System and method for recovering capacity of halogen-containing flow battery

Abstract

The invention belongs to the field of flow batteries, and discloses a system and a method for recovering the capacity of a halogen-containing flow battery, the system comprises a rebalance galvanic pile, the positive liquid of the rebalance galvanic pile circularly circulates with a rebalance storage tank through a positive pump, and the negative liquid of the rebalance galvanic pile circularly circulates with an electrolyte storage tank through a negative pump; the rebalancing electric pile is connected with a rebalancing power supply, and the rebalancing power supply, the positive electrode pump and the negative electrode pump are all in signal connection with the system controller. Charging is started on the basis of the ion average valence state, charging is stopped on the basis of the charging capacity, the current intensity and the charging time of the rebalance power supply are limited on the basis of the decomposition rate of the downstream hypohalous acid, cyclic utilization of halogen is guaranteed, and meanwhile the system controller is additionally arranged to control starting and stopping of the power supply and the charging intensity. And automatic online recovery of the capacity of the energy storage system of the halogen-containing flow battery is realized.

Description

Technical Field

[0001] The present application belongs to the field of liquid flow batteries, and in particular, relates to a system and method for restoring the capacity of a halogen-containing liquid flow battery. Background Art

[0002] Liquid flow battery is a new type of large-scale electrochemical energy storage device. It stores electrical energy in electrolyte solution during charging and converts the stored energy into electrical energy during discharge. The output power of the battery depends on the size and number of battery stacks, and the storage capacity depends on the concentration and volume of the electrolyte. During the battery charging and discharging process, only the ion valence state in the positive and negative electrolytes changes. The electrolyte can be recycled and reused, and the operation is safe.

[0003] During the long-term operation of liquid flow batteries, the occurrence of side reactions such as hydrogen evolution will cause an imbalance in ion valence, resulting in a decrease in battery capacity, performance, and service life. Therefore, it is usually necessary to restore the ion valence and substances regularly. For sulfuric acid-based systems represented by all-vanadium liquid flow batteries, recovery is often carried out by adding reducing agents or electrolysis. However, for hydrochloric acid-based systems represented by iron-chromium liquid flow batteries, and other liquid flow battery systems containing elements such as chlorine Cl, bromine Br, and iodine I, due to the relatively low reduction potential of halogens, the reduction reaction required by the battery cannot be carried out independently, and is inevitably accompanied by the generation of halogen elements, and is affected by the battery temperature and escapes from the system in the form of gas, causing a variety of adverse effects.

[0004] Therefore, researching and designing a method for realizing capacity recovery in an efficient, convenient and easy-to-operate manner is currently one of the focuses of researchers in this field. Summary of the invention

[0005] In order to overcome the defects of the above-mentioned prior art, the present application provides a system and method for automatically restoring the capacity of a halogen-containing liquid flow battery online.

[0006] To achieve the above objectives, this application provides the following technical solutions:

[0007] A system for restoring the capacity of a halogen-containing liquid flow battery comprises a rebalancing stack, wherein the positive electrode liquid of the rebalancing stack circulates with a rebalancing tank via a positive electrode pump, and the negative electrode liquid of the rebalancing stack circulates with an electrolyte tank via a negative electrode pump. The rebalancing stack is connected to a rebalancing power supply, and the rebalancing power supply, the positive electrode pump and the negative electrode pump are all connected to a system controller signal.

[0008] Furthermore, an ion valence detector is provided in the electrolyte storage tank, and the ion valence detector is connected to the system controller signal.

[0009] Furthermore, a spray unit is provided on the top of the tank body of the rebalancing tank, and the positive electrode liquid enters the rebalancing tank through the spray unit. A gas sensor is provided upstream of the spray unit, and the gas sensor is connected to the system controller signal.

[0010] Furthermore, an ultraviolet light source is provided in the tank body of the rebalancing tank, and the ultraviolet light source is connected to the system controller signal.

[0011] Furthermore, the center of the tank body of the rebalance tank is filled with catalyst filler.

[0012] Furthermore, the top of the rebalancing tank is connected to the alkali absorption tank, and an exhaust pipe is arranged on the top of the alkali absorption tank.

[0013] Furthermore, an exposure tank is provided between the rebalancing tank and the cathode pump, and the exposure tank and the rebalancing tank are cyclically connected via a gas phase connecting pipe and a liquid phase connecting tank.

[0014] Furthermore, the exposure pool is sealed with a transparent top cover.

[0015] The present application also discloses a method for recovering the capacity of a halogen-containing liquid flow battery, which recovers the capacity of a halogen-containing liquid flow battery based on the above-mentioned system.

[0016] Further, a method for restoring the capacity of a halogen-containing flow battery comprises:

[0017] The charging capacity is calculated based on the average valence state of the active ions monitored by the ion valence detector, and the system controller controls the opening of the rebalancing power supply based on whether the average valence state of the active ions reaches a preset valence state, and controls the closing of the rebalancing power supply based on whether the charging capacity reaches a preset capacity;

[0018] The system controller adjusts the current intensity of the rebalancing power supply and the light intensity of the ultraviolet light source to control the generation rate of hypohalous acid to be equal to the decomposition rate.

[0019] Technical effects and advantages of this application:

[0020] 1. This application starts charging based on the average valence state of ions, stops charging based on charging capacity, limits the current intensity and charging time of the power supply based on the decomposition rate of downstream hypohalous acid, ensures the recycling of halogens, and adds a system controller to control the start and stop of the power supply and the charging intensity, so as to realize automatic online recovery of the capacity of the halogen-containing liquid flow battery energy storage system.

[0021] 2. This application is applicable to capacity recovery of halogen-containing flow battery energy storage systems and projects of various sizes without the need to supplement reducing agents.

[0022] 3. This application can utilize sunlight to decompose hypohalite, which is energy-saving and environmentally friendly.

[0023] Other features and advantages of the present application will be described in the following description, and partly become apparent from the description, or be understood by practicing the present application. The purpose and other advantages of the present application can be realized and obtained by the structures indicated in the description, claims and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a schematic structural diagram of a system for recovering the capacity of a halogen-containing liquid flow battery according to the present application.

[0025] Figure numerals: 1. electrolyte storage tank; 2. rebalancing tank; 3. negative electrode pump; 4. positive electrode pump; 5. rebalancing stack; 6. rebalancing power supply; 7. spray unit; 8. catalyst filler; 9. ultraviolet light source; 10. alkali absorption tank; 11. exhaust pipe; 12. gas sensor; 13. liquid phase connecting pipe; 14. gas phase connecting pipe; 15. exposure tank; 16. transparent top cover; 17. ion valence detector; 18. system controller. DETAILED DESCRIPTION

[0026] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0027] like Figure 1 As shown, the present application provides a system for restoring the capacity of a halogen-containing liquid flow battery, including a rebalancing stack 5, wherein the positive electrode liquid of the rebalancing stack 5 circulates with the rebalancing tank 2 via a positive electrode pump 4, and the negative electrode liquid of the rebalancing stack 5 circulates with the electrolyte tank 1 via a negative electrode pump 3, and the rebalancing stack 5 is connected to a rebalancing power supply 6, and the rebalancing power supply 6, the positive electrode pump 4 and the negative electrode pump 3 are all connected to the system controller 18 signal.

[0028] In some embodiments of the present application, an ion valence detector 17 is provided in the electrolyte storage tank 1 , and the ion valence detector 17 is signal-connected to the system controller 18 for real-time monitoring of the average valence of active ions in the electrolyte storage tank 1 .

[0029] In some embodiments of the present application, a spray unit 7 is provided at the top of the tank of the rebalance tank 2, and the cathode liquid enters the rebalance tank 2 through the spray unit 7. An ultraviolet light source 9 is provided in the tank of the rebalance tank 2, and the ultraviolet light source 9 is located below the spray unit 7. The cathode liquid is transformed into small droplets by the spray unit 7. Under the irradiation of the ultraviolet light source 9, the hypohalous acid in the cathode liquid is decomposed into oxygen and hydrogen halide. A gas sensor 12 is provided upstream of the spray unit 7 to monitor the gas content in the cathode liquid, so as to determine the generation rate of hypohalous acid in the cathode liquid. The gas sensor 12 is connected to the system controller 18 by signal, and the ultraviolet light source 9 is also connected to the system controller 18 by signal. The system controller 18 controls the decomposition rate of hypohalous acid by adjusting the light intensity of the ultraviolet light source 9. The generation rate of hypohalous acid is adjusted by adjusting the current intensity of the rebalance power supply to ensure that the generation rate of hypohalous acid is equal to the decomposition rate, so that the halogen element does not overflow the system, and the recycling of halogen is ensured.

[0030] In some embodiments of the present application, the center of the tank body of the rebalance storage tank 2 is filled with a catalyst filler 8, and the catalyst may contain a transition metal oxide, such as Co2O3, to further promote the decomposition of hypohalous acid.

[0031] In some embodiments of the present application, the top of the rebalancing tank 2 is connected to the alkali absorption tank 10, and an exhaust pipe 11 is provided on the top of the alkali absorption tank 10. The oxygen generated by the decomposition of hypohalous acid is purified by alkali liquid and discharged through the exhaust pipe 11.

[0032] In some embodiments of the present application, an exposure pool 15 is provided between the rebalancing tank 2 and the cathode pump 4, and the exposure pool 15 and the rebalancing tank 2 are circulated and connected through the gas phase connecting pipe 14 and the liquid phase connecting pipe 13. The cathode pump 4 pumps the liquid in the exposure pool 16 into the cathode of the rebalancing stack 5, and then returns to the rebalancing tank 2 through the spray unit 7, and then returns to the exposure pool 15 along the liquid phase connecting pipe 13; the hypohalite contained in the solution in the exposure pool 15 decomposes under sunlight to generate oxygen and hydrogen halide, and the oxygen precipitates and enters the rebalancing tank 2 along the gas phase connecting pipe 14, and then is discharged through the alkali absorption tank 10 and the exhaust pipe 11. The exposure pool 15 is sealed with a transparent top cover 16. Preferably, quartz glass or a fluorine-containing transparent polyimide plastic film can be selected, and ultraviolet lamps and catalyst particles can also be installed in the exposure pool 15 to further promote the decomposition of hypohalite and provide decomposition capacity at night or on cloudy days.

[0033] The present application also provides a method for restoring the capacity of a halogen-containing liquid flow battery, which restores the capacity of a halogen-containing liquid flow battery based on the system described in the claims.

[0034] When the main system is charged and discharged, the valence states of the first active ions (M) and the second active ions (N) change repeatedly. Due to the hydrogen evolution side reaction in the aqueous flow battery, the average ion valence state of the electrolyte will gradually increase, and it is necessary to start the rebalancing system to restore the solution ion valence state and replenish hydrogen ions at the same time. The rebalancing tank 2 contains an acid solution containing hydrochloric acid and / or hydrobromic acid, which is consistent with the halogen composition of the main system, and may also contain the first active ions and / or the second active ions. The negative electrode liquid of the rebalancing stack 5 comes from the electrolyte storage tank 1 to be restored, and the positive electrode liquid comes from the rebalancing tank 2, which are circulated through the negative electrode pump 3 and the positive electrode pump 4 respectively. The ion valence detector 17 monitors the average valence state of the first / second active ions in the storage tank 1 at the end of the main system discharge, and feeds back to the system controller 18, which is recorded as M m+ / N n+ , taking the electrolyte storage tank 1 as the main system positive electrode electrolyte, containing the first active ion M as an example (the same applies to the negative electrode), the system controller 18 determines whether the average valence state m of the first active ion M is greater than or equal to x, where x is a preset valence state. When m≥x, the system controller 18 starts the rebalancing power supply 6, the positive electrode pump 4 and the negative electrode pump 3 to charge the rebalancing stack 5, and its charging capacity is recorded as Q (Ah). The system controller 18 turns off the rebalancing power supply 6 when it determines that Q meets the following conditions: Q=26.8*C (M) *V (M) *(mx), where C (M) is the total ion concentration of the first active ion M in the solution; V (M) is the total volume of the solution in the electrolyte storage tank 1; m is the average valence state of the first active ion M; x is the preset valence state set by the system. During the period when the rebalancing power supply 6 charges the rebalancing stack 5, the positive electrode of the rebalancing stack 5 produces chlorine and / or bromine and / or iodine, which dissolve in the solution and react with water to generate their hydrides and hypohalous acid. The general reaction formula is X2+H2O=HX+HXO (X is a halogen atom). The electrolyte enters the rebalancing tank 2, and the negative electrode of the rebalancing stack 5 undergoes a reduction reaction synchronously, and the high-valence first active ion (M a+ ) obtains electrons to generate the first active ion (M c+ ), that is, capacity recovery is achieved. The reactions involved in the positive electrode are: 2X - -2e-→X2, X2+H2O→HX+HXO, the total reaction at the positive electrode is: X - +H2O-2e-→H + +HXO; the negative electrode reaction is M a+ +e-→M c+ .

[0035] During the period when the rebalanced power supply 6 charges the rebalanced battery stack 5, the gas sensor 13 synchronously monitors the gas concentration in the positive electrode liquid entering the rebalanced storage tank 2. The positive electrode liquid is sprayed into small droplets by the spray unit 7 and enters the rebalanced storage tank 2. The system controller 18 controls the ultraviolet lamp 10 to irradiate the small droplets. The hypohalous acid in the positive electrode liquid is decomposed into oxygen and hydrogen halide. The reaction equation is: 2HXO→2HX+O2↑, the decomposition rate of hypohalous acid V1=k*S*C, where k is the hypohalous acid photolysis rate constant, S is the light intensity, C is the hypohalous acid concentration, and the hypohalous acid generation rate V2=0.0185*I, where I is the current intensity of the rebalanced battery stack 5. By adjusting S and I through the system controller 18, and controlling the irradiation time T1 and the charging time T2 at the same time, it can be ensured that V1*T1=V2*T2, so that the halogen element does not overflow the system, and the recycling of the halogen is guaranteed. For the overall system, the equivalent total reaction equation is: 4M a+ +2H2O→4M c+ +O2↑+4H + or 4N b+ +2H2O→4N d+ +O2↑+4H + .

[0036] In summary, the present application starts charging based on the average valence state of the ions, stops charging based on the charging capacity, limits the current intensity and charging time of the power supply based on the decomposition rate of the downstream hypohalous acid, ensures the recycling of halogens, and adds a system controller to control the start and stop of the power supply and the charging intensity, thereby realizing automatic online recovery of the capacity of the halogen-containing liquid flow battery energy storage system.

[0037] Finally, it should be noted that the above is only a preferred embodiment of the present application and is not intended to limit the present application. Although the present application has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A system for restoring the capacity of a halogen-containing flow battery, characterized in that: The invention comprises a rebalancing stack (5), wherein the positive electrode liquid of the rebalancing stack (5) circulates with the rebalancing tank (2) through a positive electrode pump (4), and the negative electrode liquid of the rebalancing stack (5) circulates with the electrolyte tank (1) through a negative electrode pump (3). The rebalancing stack (5) is connected to a rebalancing power supply (6), and the rebalancing power supply (6), the positive electrode pump (4) and the negative electrode pump (3) are all connected to the system controller (18) by signal.

2. A system for recovering the capacity of a halogen-containing flow battery according to claim 1, characterized in that: An ion valence detector (17) is arranged in the electrolyte storage tank (1), and the ion valence detector (17) is connected to the system controller (18) by signal.

3. A system for recovering the capacity of a halogen-containing flow battery according to claim 1, characterized in that: A spray unit (7) is provided at the top of the tank body of the rebalancing tank (2), and the positive electrode liquid enters the rebalancing tank (2) through the spray unit (7). A gas sensor (12) is provided upstream of the spray unit (7), and the gas sensor (12) is connected to the system controller (18) by signal.

4. A system for recovering the capacity of a halogen-containing flow battery according to claim 1, characterized in that: An ultraviolet light source (9) is arranged in the tank body of the rebalancing tank (2), and the ultraviolet light source (9) is connected to the system controller (18) via a signal.

5. A system for recovering the capacity of a halogen-containing flow battery according to claim 1, characterized in that: The center of the tank body of the rebalancing tank (2) is filled with a catalyst filler (8).

6. A system for recovering the capacity of a halogen-containing flow battery according to claim 1, characterized in that: The top of the rebalancing storage tank (2) is connected to the alkali absorption tank (10), and the top of the alkali absorption tank (10) is provided with an exhaust pipe (11).

7. A system for recovering the capacity of a halogen-containing flow battery according to claim 1, characterized in that: An exposure pool (15) is provided between the rebalancing tank (2) and the cathode pump (4), and the exposure pool (15) and the rebalancing tank (2) are cyclically connected via a gas phase connecting pipe (14) and a liquid phase connecting pipe (13).

8. A system for recovering the capacity of a halogen-containing flow battery according to claim 7, characterized in that: The exposure pool (15) is sealed with a transparent top cover (16).

9. A method for restoring the capacity of a halogen-containing flow battery, characterized in that: The method recovers the capacity of a halogen-containing flow battery based on the system described in any one of claims 1 to 8.

10. A method for restoring the capacity of a halogen-containing redox flow battery according to claim 9, characterized in that: include: The charging capacity is calculated based on the average valence state of the active ions monitored by the ion valence state detector (17), and the system controller (18) controls the opening of the rebalancing power supply (6) based on whether the average valence state of the active ions reaches a preset valence state, and controls the closing of the rebalancing power supply (6) based on whether the charging capacity reaches a preset capacity; The system controller (18) adjusts the current intensity of the rebalancing power supply (6) and the illumination intensity of the ultraviolet light source (10) to control the generation rate of hypohalous acid to be equal to the decomposition rate.

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