Integrated flow battery capacity recovery system and method

Abstract

The invention discloses an integrated flow battery capacity recovery system and method, and belongs to the technical field of electrochemical energy storage. The integrated flow battery capacity recovery system comprises a main system stack and a rebalance stack, two ends of the main system stack are respectively connected with a positive storage tank and a negative storage tank, the positive storage tank is filled with a reducing agent, one end of the rebalance stack is connected with the positive storage tank, and the other end of the rebalance stack is connected with the negative storage tank. An adjusting device is arranged between the positive storage tank and the positive inlet of the rebalancing galvanic pile; the integrated flow battery capacity recovery system further comprises a charging and discharging device, and the charging and discharging device is connected with the main system electric pile and the rebalance electric pile. The integrated flow battery capacity recovery system and the integrated flow battery capacity recovery method effectively solve the problems that most reducing agents cannot directly react, and halogen simple substances are generated by adopting an electrolysis mode, and the liquid in the system is utilized to absorb halogen gas generated in the capacity recovery process, so that internal recycling is realized, and the energy consumption is reduced. The solution component stability is ensured.

Description

Technical Field

[0001] The present invention relates to the technical field of electrochemical energy storage, and in particular to an integrated liquid flow battery capacity recovery system and method. 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 the flow battery, the occurrence of side reactions such as hydrogen evolution will cause an imbalance in the ion valence state, resulting in a decrease in battery capacity, reduced performance, and shortened service life. Therefore, it is usually necessary to restore the ion valence state and substances regularly. For the sulfuric acid-based system represented by the all-vanadium flow battery, recovery is mostly carried out by adding a reducing agent or electrolysis. However, for the hydrochloric acid-based system represented by the iron-chromium flow battery, and other flow battery systems containing elements such as chlorine Cl, bromine Br, and iodine I, due to the relatively low reduction potential of the halogen, 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 a gaseous form, causing a variety of adverse effects. Therefore, designing a unique method and system to restore the active ion concentration of the positive and negative electrode electrolytes to the initial state so that the battery system capacity can be restored is one of the key research and development technologies of the iron-chromium flow battery.

[0004] In the early research of NASA's iron-chromium flow battery system, Fe 3+ -H2 rebalances the battery to achieve capacity recovery, but its hydrogen electrode requires the use of Pt (platinum) or W (tungsten) catalysts, and Pt will penetrate into the negative electrode electrolyte through the ion membrane, thereby contaminating the negative electrode electrolyte. In addition, Pt is relatively expensive and not suitable for industrial applications; W catalysts have poor stability and will deactivate after a period of use. Patent No. CN105702997A discloses a liquid flow battery rebalancing system and a liquid flow battery system and a method for rebalancing the circulating capacity of a liquid flow battery, which specifically discloses a method for reducing Fe by electrolytic reduction of a rebalanced battery. 3+ The positive electrode solution of the rebalanced battery is a positive electrode electrolyte containing active cations, and the negative electrode solution is a positive electrode storage tank of the main system flow battery. However, the cost of the rebalanced solution in this method is high, and each rebalancing requires draining the waste liquid, filling with new liquid, and treating the waste liquid. The labor cost and waste liquid treatment cost are also high.

[0005] 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

[0006] The purpose of the present invention is to provide an integrated liquid flow battery capacity recovery system and method, which is used to solve the technical problems in the prior art of liquid flow battery capacity recovery methods that the reducing agent cannot react directly and the halogen elements escape from the system in gaseous form.

[0007] To achieve the above-mentioned purpose, an embodiment of the present invention provides an integrated liquid flow battery capacity recovery system, comprising a main system stack and a rebalancing stack, wherein the two ends of the main system stack are respectively connected to a positive electrode storage tank and a negative electrode storage tank, the positive electrode storage tank is filled with a reducing agent, one end of the rebalancing stack is connected to the positive electrode storage tank, and an adjusting device is provided between the positive electrode storage tank and the positive electrode inlet of the rebalancing stack;

[0008] The integrated liquid flow battery capacity recovery system also includes charging and discharging equipment, which is connected to the main system stack and the rebalancing stack.

[0009] In one of the preferred solutions of the present invention, the main system stack and the rebalancing stack are connected in parallel, and a DC switch is provided between the main system stack and the rebalancing stack.

[0010] In one of the preferred embodiments of the present invention, the reducing agent includes at least one of formic acid, methanol, ethanol, acetic acid, oxalic acid, hydrogen peroxide, ascorbic acid, hydrazine hydrate, ammonia water and urea.

[0011] In one of the preferred solutions of the present invention, a positive electrode pump is provided between the positive electrode storage tank and the main system stack and the rebalancing stack, and a negative electrode pump is provided between the negative electrode storage tank and the main system stack.

[0012] In one of the preferred solutions of the present invention, the positive electrode storage tank is connected with a connecting pipe, one end of the connecting pipe away from the positive electrode storage tank is connected with the negative electrode storage tank, and an exhaust pipe is arranged on the negative electrode storage tank.

[0013] In one of the preferred solutions of the present invention, the regulating device is a regulating valve.

[0014] In one of the preferred solutions of the present invention, one end of the rebalancing stack away from the positive electrode storage tank is connected to the negative electrode storage tank, and a negative electrode pump is provided between the negative electrode storage tank and the rebalancing stack.

[0015] In one of the preferred solutions of the present invention, a bubbler is provided inside the positive electrode storage tank, one end of the bubbler is connected to a gas-liquid mixer, and the gas-liquid mixer is connected to the positive electrode outlet of the rebalancing stack and the positive electrode outlet of the main system stack.

[0016] One of the preferred solutions of the present invention is to combine the main system stack and the rebalancing stack into a combined stack, the combined stack includes a plurality of main system cells and a plurality of rebalancing cells, each main system cell includes a main system battery positive electrode, each rebalancing cell includes a rebalancing battery positive electrode, and a resistance member is provided in the battery flow channel of the rebalancing battery positive electrode.

[0017] In one of the preferred solutions of the present invention, the resistance member includes a screw, one end of which passes through the combined battery stack and extends into the battery flow channel of the positive electrode of the rebalancing battery.

[0018] Based on an integrated liquid flow battery capacity recovery system disclosed in the present invention, the present invention also discloses an integrated liquid flow battery capacity recovery method, comprising the following steps: a regulating device regulates the flow entering the rebalancing stack so that the voltage reaches the reaction voltage of the reducing agent in the positive electrode storage tank, the electrolyte after the positive electrode reaction of the rebalancing stack flows out from the positive electrode outlet of the rebalancing stack, then flows into the rebalancing stack from the negative electrode inlet of the rebalancing stack, and finally flows out from the negative electrode outlet of the rebalancing stack and returns to the positive electrode storage tank, thereby realizing capacity recovery of the main system battery.

[0019] In one of the preferred schemes of the present invention, the product of the positive electrode reaction of the rebalancing stack directly enters the negative electrode of the rebalancing stack, and a reverse reaction occurs at the negative electrode of the rebalancing stack, and the halogen element obtains electrons and turns back into halogen ions, thereby realizing self-circulation of halogen ions in the rebalancing system.

[0020] In summary, the beneficial effects of the present invention are:

[0021] 1. The integrated liquid flow battery capacity recovery system of the present invention adjusts the flow rate flowing into the rebalancing stack through an adjusting device so that the voltage reaches the reaction voltage of the reducing agent in the positive electrode storage tank. The electrolyte after the positive electrode reaction of the rebalancing stack flows out from its positive electrode outlet, then flows into the rebalancing stack from its negative electrode inlet, and finally flows out from its negative electrode outlet and returns to the positive electrode storage tank. By replenishing hydrogen ions and electrons into the main system battery, the charge amount of the positive and negative electrodes in the battery is adjusted, thereby realizing capacity recovery.

[0022] 2. The integrated liquid flow battery capacity recovery system and method of the present invention effectively solves the problem that most reducing agents cannot react directly and halogen elements will be produced by electrolysis. The present invention absorbs the halogen gas produced in the capacity recovery process by the liquid in the system to achieve internal circulation and ensure the stability of the solution composition. In addition, the rebalancing system and the main system for capacity recovery of the present invention are integrated into one module, which reduces the connection of pipelines outside the box and solves the problem that more equipment and long system pipelines need to be added when using an independent capacity recovery system, resulting in high system complexity and high cost. At the same time, it also greatly reduces the complexity and significantly reduces the cost.

[0023] 3. The reduction product of the reducing agent used in the integrated liquid flow battery capacity recovery system of the present invention is a non-toxic and harmless gas (such as nitrogen, carbon dioxide, etc.), which does not require post-treatment (such as alkaline solution absorption) and can be separated from the system by itself. There is no need to add a separate separation process unit, and no "three wastes" are generated.

[0024] 4. The integrated liquid flow battery capacity recovery system of the present invention adjusts the overpotential of the reducing agent and the active ions of the main system by changing the flow rate, thereby achieving the adaptation voltage of the reducing agent and the active ions of the main system to achieve the same cutoff condition and realize the sharing of equipment with the main system module.

[0025] 5. The integrated liquid flow battery capacity recovery system and method of the present invention is suitable for large-scale engineering applications. It is an integrated automatic online recovery of the capacity of halogen-containing liquid flow battery energy storage system rebalancing process system, and is suitable for iron-chromium liquid flow batteries, hydrochloric acid all-vanadium liquid flow batteries and other halogen-containing liquid flow batteries and other energy storage systems.

[0026] 6. The integrated liquid flow battery capacity recovery system of the present invention performs efficient step-by-step electrolytic reduction of excess high-valent positive / negative active reaction materials in the electrolyte to balance the charge state and storage capacity of the positive and negative electrolytes and restore the system electrolyte to its initial state, thereby restoring the performance and capacity of the liquid flow battery to its initial state.

[0027] Other features and advantages of the present invention will be described in the following description, and part of them will become obvious from the description, or will be understood by implementing the present invention. The purpose and other advantages of the present invention can be described by the effects described in the description and the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a schematic diagram of the structure of the integrated liquid flow battery capacity recovery system in Example 1 of the present invention;

[0029] Figure 2 This is a schematic diagram of the structure of the integrated flow battery capacity recovery system in Example 2 of the present invention;

[0030] Figure 3 This is a schematic diagram of the structure of the combined battery stack in Example 3 of the present invention;

[0031] Figure 4 A schematic diagram of inserting a resistance member from the edge of a plate frame of a combined battery stack in Example 3 of the present invention;

[0032] Figure 5 A schematic diagram of inserting a resistance member from the end of a combined battery stack in Example 3 of the present invention;

[0033] Figure 6 1 is a diagram showing the operating effect of the system in an embodiment of the present invention.

[0034] Among them, 1-positive electrode storage tank, 2-connecting pipe, 3-exhaust pipe, 4-negative electrode storage tank, 5-negative electrode pump, 6-liquid flow battery power module, 7-charging and discharging equipment, 8-positive electrode pump, 9-main system battery stack, 10-DC switch, 11-rebalancing battery stack positive electrode outlet, 12-rebalancing battery stack negative electrode inlet, 13-rebalancing battery stack, 14-rebalancing battery stack negative electrode outlet, 15-regulating valve, 16-rebalancing battery stack positive electrode inlet, 17-gas-liquid mixer, 18-bubbler, 19-main system battery positive electrode, 20-battery flow channel, 21-resistance piece, 22-rebalancing battery positive electrode, 23-screw, 24-sealing ring. DETAILED DESCRIPTION

[0035] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. 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.

[0036] The present invention provides an integrated liquid flow battery capacity recovery system, including a main system stack 9 and a rebalancing stack 13, wherein the two ends of the main system stack 9 are respectively connected to a positive electrode storage tank 1 and a negative electrode storage tank 4, and the positive electrode storage tank 1 is filled with a reducing agent.

[0037] The reducing agent is a compound containing hydrogen and / or carbon and / or nitrogen and / or oxygen elements which can be reduced (i.e., the valence state of the element can be increased), does not contain the same halogen elements as the main system, and the reduction product generated by it is a gas. The reducing agent itself can be solid, liquid or gas, such as formic acid, methanol, ethanol, acetic acid, oxalic acid, hydrogen peroxide, ascorbic acid, hydrazine hydrate, ammonia water, urea, etc. Take the iron-chromium flow battery as an example: when the reducing agent is formic acid, the chemical reaction equation is: 2FeCl3+HCOOH=2FeCl2+CO2+2HCl; when the reducing agent is methanol, the chemical reaction equation is: 6FeCl3+CH3OH+H2O=6FeCl2+CO2+6HCl; when the reducing agent is ethanol, the chemical reaction equation is: 12FeCl3+C2H5OH+3H2O=12FeCl2+2CO2+12HCl; when the reducing agent is acetic acid, the chemical reaction equation is: 8FeCl3+CH4O2=8FeCl2+2CO2+8HCl; when the reducing agent is ethanol, the chemical reaction equation is: 12FeCl3+C2H5OH+3H2O=12FeCl2+2CO2+12HCl; when the reducing agent is acetic acid, the chemical reaction equation is: 8FeCl3+CH4O2=8FeCl2+2CO2+8HCl; When the original agent is oxalic acid, the chemical reaction equation is: 2FeCl3+H2C2O4=2FeCl2+2CO2+2HCl; when the reducing agent is hydrogen peroxide, the chemical reaction equation is: 2FeCl3+H2O2=2FeCl2+HCl+O2; when the reducing agent is ascorbic acid, the chemical reaction equation is: 2FeCl3+C6H8O6=2FeCl2+C6H6O6+2HCl; when the reducing agent is hydrazine hydrate, the chemical reaction equation is: 4FeCl3+N2H4=4FeCl2+N2+4HCl; when the reducing agent is ammonia or urea, the chemical reaction equation is: 2NH4 + + 6FeCl3=6FeCl2+N2+6HCl+6H + .

[0038] One end of the rebalancing stack 13 is connected to the positive electrode storage tank 1, and a regulating device is provided between the positive electrode storage tank 1 and the positive electrode inlet of the rebalancing stack 13. The regulating device here is used to regulate the flow of electrolyte entering the positive electrode inlet 16 of the rebalancing stack. Preferably, the regulating device is a regulating valve 15. The integrated liquid flow battery capacity recovery system changes the flow entering the positive electrode inlet 16 of the rebalancing stack through the regulating device, so that it is in a state of low flow and large concentration polarization, so that its overpotential is increased, so that the voltage reaches the reaction voltage of the reducing agent.

[0039] The integrated liquid flow battery capacity recovery system further includes a charging and discharging device 7 , which is connected to the main system stack 9 and the rebalancing stack 13 .

[0040] The main system stack 9 and the rebalancing stack 13 are connected in parallel, and the operating voltage ranges of the main system stack 9 and the rebalancing stack 13 are made close by matching the appropriate number of nodes; and a DC switch 10 is provided between the main system stack 9 and the rebalancing stack 13. The DC switch 10 is used to disconnect when the voltage ranges do not match during discharge and charging, and to control the charging time of the rebalancing stack 13, thereby controlling the recovery amount.

[0041] A positive electrode pump 8 is provided between the positive electrode storage tank 1 and the main system stack 9 and the rebalancing stack 13, and a negative electrode pump 5 is provided between the negative electrode storage tank 4 and the main system stack 9. The positive electrode pump 8 pumps the electrolyte in the positive electrode storage tank 1 into the positive electrode inlet of the main system stack 9 and the rebalancing stack 13, and the negative electrode pump 5 pumps the electrolyte in the negative electrode storage tank 4 into the negative electrode inlet of the main system stack 9. Furthermore, the end of the rebalancing stack 13 away from the positive electrode storage tank 1 is connected to the negative electrode storage tank 4, and a negative electrode pump 5 is provided between the negative electrode storage tank 4 and the rebalancing stack 13. The negative electrode of the rebalancing stack 13 can be connected to the positive electrode electrolyte of the main system, and can also be connected to the negative electrode electrolyte of the main system.

[0042] The positive electrode storage tank 1 is connected to a connecting pipe 2, and one end of the connecting pipe 2 away from the positive electrode storage tank 1 is connected to the negative electrode storage tank 4, and an exhaust pipe 3 is provided on the negative electrode storage tank 4. The gas in the positive electrode storage tank 1 enters the negative electrode storage tank 4 through the connecting pipe 2, and is replaced with the byproduct hydrogen generated by the charging and discharging of the main system in the negative electrode storage tank 4, and the byproduct hydrogen is discharged through the exhaust pipe 3.

[0043] Furthermore, a bubbler 18 is provided inside the positive electrode storage tank 1, one end of which is connected to a gas-liquid mixer 17, and the gas-liquid mixer 17 is connected to the positive electrode outlet of the rebalanced stack 13 and the positive electrode outlet of the main system stack 9. The halogen gas in the positive electrode storage tank 1 can be discharged through the bubbler 18, and the halogen element and the Fe in the positive electrode storage tank 1 2+ The halogen ions can be converted back into halogen ions by reaction, and the halogen element gas can also be absorbed in advance by the gas-liquid mixer 17 before returning to the positive electrode storage tank 1.

[0044] Further, the main system stack 9 and the rebalancing stack 13 are combined into a combined stack, which includes a plurality of main system cells and a plurality of rebalancing cells, each of which includes a main system cell positive electrode 19, each of which includes a rebalancing cell positive electrode 22, each of which includes a main system cell positive electrode 19 and each of which includes a rebalancing cell positive electrode 22, each of which includes a positive electrode inlet and a positive electrode outlet, each of which includes a plurality of battery flow channels 20. A resistance member 21 is provided in the battery flow channel 20 of the rebalancing cell positive electrode 22, and the resistance member 21 includes a screw 23, one end of which penetrates the combined stack and extends into the battery flow channel 20 of the rebalancing cell positive electrode 22. A sealing ring 24 is provided between the screw 23 and the positive plate frame of the combined stack.

[0045] The main system stack 9 and the rebalancing stack 13 as well as the regulating device, switch and circulating pump therebetween together constitute the liquid flow battery power module 6 .

[0046] Working process: Electrolyte is stored in both the positive electrode storage tank 1 and the negative electrode storage tank 4. When the main system stack 9 is charged and discharged, the valence state of the ions in the electrolyte changes repeatedly under the action of the positive electrode pump 8 and the negative electrode pump 5. Due to a small amount of irreversible side reactions, excess ions will continue to accumulate in the positive electrode storage tank 1. At this time, the regulating device adjusts the flow of the electrolyte entering the positive electrode storage tank 1 to rebalance the stack 13, so that the voltage reaches the reaction voltage of the reducing agent in the positive electrode storage tank 1. The electrolyte that has completed the positive electrode reaction of the rebalancing stack 13 flows out from the positive electrode outlet 11 of the rebalancing stack, and then flows into the rebalancing stack 13 from the negative electrode inlet 12 of the rebalancing stack, and finally flows out from the negative electrode outlet 14 of the rebalancing stack and returns to the positive electrode storage tank 1. By replenishing hydrogen ions and electrons in the main system battery, the charge amount of the positive and negative electrodes in the main system battery is adjusted, thereby realizing capacity recovery.

[0047] The present invention also discloses an integrated liquid flow battery capacity recovery method, which is implemented based on the above-mentioned integrated liquid flow battery capacity recovery system, and includes the following steps: a regulating device adjusts the flow entering the rebalancing stack 13 so that the voltage reaches the reaction voltage of the reducing agent in the positive electrode storage tank 1, and the electrolyte after the positive electrode reaction of the rebalancing stack 13 flows out from the positive electrode outlet 11 of the rebalancing stack, and then flows into the rebalancing stack 13 from the negative electrode inlet 12 of the rebalancing stack, and finally flows out from the negative electrode outlet 14 of the rebalancing stack and returns to the positive electrode storage tank 1, thereby realizing the capacity recovery of the main system battery.

[0048] Furthermore, the product of the positive electrode reaction of the rebalancing stack 13 directly enters the negative electrode of the rebalancing stack 13, where a reverse reaction occurs, and the halogen element obtains electrons and turns back into halogen ions, thereby realizing self-circulation of halogen ions in the rebalancing system.

[0049] Example: Taking the iron-chromium flow battery as an example:

[0050] Example 1: An integrated flow battery capacity recovery system, such as Figure 1 As shown, the specific working process is:

[0051] (1) The positive electrode storage tank 1 and the negative electrode storage tank 4 contain electrolytes rich in Fe and Cr ions. When the main system stack 9 is charged and discharged, the valence states of Fe and Cr ions change repeatedly. Due to a small amount of irreversible side reactions, excess Fe ions will continue to accumulate in the positive electrode storage tank 1. 3+ ion;

[0052] (2) A reducing agent is added to the positive electrode storage tank 1. The reducing agent is a compound containing hydrogen and / or carbon and / or nitrogen and / or oxygen elements that can be reduced (i.e., the valence state of the element can be increased) (chemical formula: H a C b O c N d , wherein a is 0-4, b is 0-4, c is 0-4, and d is 0-4), the reducing agent itself can be solid, liquid or gas, or a mixture of the above substances; usually, only a very small amount of the reducing agent can directly react with Fe 3+ The reaction proceeds, so most of the reducing agent remains dissolved in the electrolyte, and the reducing agent component should not adversely affect the charging and discharging of the main system;

[0053] (3) The rebalancing stack 13 is connected in parallel with the main system stack 9 circuit, and the operating voltage ranges thereof are close by matching the appropriate number of nodes; a DC switch 10 is also provided between the rebalancing stack 13 and the main system stack 9, and the DC switch 10 is disconnected when the voltage ranges do not match during discharge and charging, and the DC switch 10 also controls the charging time of the rebalancing stack 13, thereby controlling the recovery amount;

[0054] (4) The positive electrode pump 8 delivers the positive electrode electrolyte to the main system stack 9 and the rebalancing stack 13, and changes the flow rate entering the positive electrode inlet 16 of the rebalancing stack through the regulating valve 15, so that it is in a state of low flow rate and large concentration polarization, so that its overpotential is increased, so that the voltage reaches the reaction voltage of the reducing agent, and the electrolyte of the rebalancing stack 13 that has completed the positive electrode reaction flows out from the positive electrode outlet 11 of the rebalancing stack, and then flows into the rebalancing stack 13 from the negative electrode inlet 12 of the rebalancing stack, and finally flows out from the negative electrode outlet 14 of the rebalancing stack and returns to the positive electrode storage tank 1;

[0055] (5) The positive electrode reaction of the rebalancing stack 13 includes: Fe 2+ Loses electrons to Fe 3+ ; The reducing agent R loses electrons to generate oxidized substances (N2 and / or CO2); The halogen ions lose electrons to become halogen elements; The reaction equation is as follows:

[0056] Positive electrode reaction:

[0057] Fe 2+ +e - =Fe 3+

[0058] aR - =bO

[0059] 2Cl - -2e - =Cl2

[0060] (6) The products of the positive electrode reaction will directly enter the negative electrode, where a reverse reaction will occur, i.e., the halogen element will gain electrons and turn back into halogen ions (i.e., the self-recycling of halogen ions is achieved in the rebalancing system). 3+ Get electrons and turn back into Fe 2+ ; N2 and CO2 are inert components, do not undergo reverse reaction, and cannot gain electrons; therefore, the positive electrode Fe 2+ To Fe 3+ The amount is less than that of negative electrode Fe 3+ Fe 2+ The total net reaction is that the reducing agent loses electrons to generate N2 or CO2, Fe 3+ Gaining electrons to generate Fe 2+ , thereby achieving capacity recovery;

[0061] Negative electrode reaction:

[0062] Fe 3+ +e - =Fe 2+

[0063] Cl2+2e - =2Cl -

[0064] Total reaction of positive and negative electrodes:

[0065] Fe 3+ +aR=Fe 2+ +bO

[0066] (7) After N2 and CO2 return to the positive electrode storage tank 1, they enter the negative electrode storage tank 4 along the connecting pipe 2 between the positive electrode storage tank 1 and the negative electrode storage tank 4, replace the by-product hydrogen generated by the charging and discharging of the main system in the negative electrode storage tank 4, and are discharged along the exhaust pipe 3 to ensure the safety of the system.

[0067] Example 2: An integrated liquid flow battery capacity recovery system, which is partially modified based on Example 1, and the specific working process is as follows:

[0068] like Figure 2 As shown, the positive electrode outlet 11 of the rebalanced stack is adjusted to return directly to the positive electrode storage tank 1 and discharged through the bubbler 18. The halogen element and the Fe 2+ Reaction, turned back into halogen ions, inert components N2 and CO2 escape from the liquid surface and then discharged, and a gas-liquid mixer 17 can also be set before returning to the positive electrode storage tank 1 to absorb the halogen elemental gas in advance;

[0069] In addition, the negative electrode of the rebalanced stack 13 can be connected to the positive electrode electrolyte of the main system, or it can be connected to the negative electrode electrolyte of the main system ( Figure 2 To connect the negative electrode tank 4);

[0070] ① When the negative electrode of the rebalanced stack 13 is connected to the positive electrode storage tank 1, the electrons generated by the positive electrode reaction of the rebalanced stack 13 are transferred to the negative electrode of the rebalanced stack 13 and are absorbed by the Fe 3+ Obtain, generate Fe 2+ , achieving capacity recovery;

[0071] ② When the negative electrode of the rebalanced stack 13 is connected to the negative electrode storage tank 4, the electrons generated by the positive electrode reaction of the rebalanced stack 13 are transferred to the negative electrode of the rebalanced stack 13 and are absorbed by the Cr in the negative electrode storage tank 4. 3+ Obtain and generate Cr 2+ , the main system can discharge more electricity, thus avoiding Fe 3+ The accumulation of can also achieve capacity recovery;

[0072] Example 3: An integrated liquid flow battery capacity recovery system, based on Example 1, combines the main system stack 9 and the rebalancing stack 13 into a combined stack.

[0073] like Figure 3 As shown, the rebalancing stack 13 and the main system stack 9 can be combined into a stack called a combined stack; the combined stack is matched with the number of single cells according to the required rebalancing rate, and the number of main system single cells is usually greater than the rebalancing single cells, such as 1-2 rebalancing cells for every 100 main system batteries. The combined stack can be used in full or in part in a set of flow battery modules;

[0074] The combined battery stack includes a plurality of main system cells and a plurality of rebalancing cells, each of which includes a main system cell positive electrode 19, and each of which includes a rebalancing cell positive electrode 22. The materials and structures of the rebalancing cells and the main system cells are essentially the same, so that the arrangement is conducive to reducing the manufacturing difficulty and cost. The main difference between the rebalancing cells and the main system cells is that a resistance member 21 is arranged in the battery flow channel 20 of the positive plate frame of the rebalancing cells, such as a plastic block, to block a part of the battery flow channel 20, thereby reducing the flow of the battery, increasing concentration polarization, and improving overpotential.

[0075] During the charging process of the battery stack, due to the high overpotential of the rebalanced single cell, its voltage increases, and the reductant and halogen on this single cell will react, lose electrons, and generate N2, CO2 and halogen elements. When flowing out of the battery stack, it will merge with the fluid of other ordinary single cells, and the halogen elements will react with the remaining Fe in the electrolyte. 2+ The inert components N2 and CO2 return to the positive electrode tank 1 and are discharged. The electrons lost by the reducing agent are replaced by Cr at the negative electrode of the battery stack. 3+ Get, generate Cr 2+ , achieving capacity recovery.

[0076] The structure of the resistance member 21 is as follows: Figure 4 and Figure 5 As shown, the resistance member 21 includes a screw 23, one end of which passes through the combined battery stack and extends into the battery flow channel 20 of the positive electrode 22 of the rebalancing battery. Specifically, the resistance member 21 is designed to be adjustable, such as a plastic member that can be inserted from the edge of the plate frame. The more it is inserted, the greater the flow resistance. At the same time, the resistance member 21 can also be inserted from the end of the combined battery stack. A sealing ring 24 can be used to seal between the resistance member 21 and the plate frame. The resistance member 21 is provided with threads for the purpose of adjustment.

[0077] By utilizing the integrated iron-chromium liquid flow battery capacity recovery system suitable for engineering applications provided by the present invention, after the system is started, it is only necessary to replenish the reducing agent in the fixed period storage tank, the operation process is simple, and the long-term operation of the battery and the efficient use of the electrolyte can be achieved.

[0078] Example

[0079] Methanol (CH4O) is used as the reducing agent, and the integrated flow battery capacity recovery system is used. Figure 1 As shown, the overall reaction is:

[0080] CH4O+H2O+6Fe 3+ =CO2+6Fe 2+ +6H +

[0081] The main system stack is 100 sections and the rebalancing stack is 80 sections.

[0082] The operating results of the system are shown in Table 1 and Figure 6 As shown:

[0083] Table 1: System operation results

[0084] state Capacity retention rate Initial state 100％ Rebalance stack switch is always off Decayed to about 80% after 50 cycles When the main system is 110V, close the switch 28 cycles to recover to about 100% When the main system is 119V, close the switch Slight decay after 20 cycles When the main system is 118V, close the switch Capacity remains basically stable

[0085] From Table 1 and Figure 6 It can be seen that the initial charging voltage of the main system is 90V. As the charging gradually increases, the DC switch of the rebalancing stack is always closed during the first 50 cycles, and the system capacity gradually decays to 80%;

[0086] Starting from the 51st cycle, when the main system charging voltage reaches 110V, the DC switch is closed and the rebalancing stack begins to charge. Since the circuit is connected in parallel, the rebalancing stack charging voltage is also 110V, which is equivalent to a single cell voltage of 1.38V. At this time, the reducing agent and halogen dissolved in the electrolyte both lose electrons, and the rebalancing stack is charged until the main system is charged to 125V.

[0087] It can be observed that the capacity gradually recovers and is close to 100% after 28 cycles, indicating that the balance rate is greater than the decay rate. At this time, the starting voltage is increased to 119V. After 20 cycles, it is found that the capacity is slightly reduced, so the starting voltage is fine-tuned to 118V. At this time, the balance speed is close to the decay speed, and the capacity remains basically stable.

[0088] In summary, the integrated liquid flow battery capacity recovery system of the present invention realizes the absorption and recycling of the halogen gas generated during the electrolysis process while restoring the capacity.

[0089] The embodiments described above are merely descriptions of preferred implementations of the present invention and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary engineering and technical personnel in the field should all fall within the protection scope of the claims of the present invention.

Claims

1. An integrated liquid flow battery capacity recovery system, characterized in that: It comprises a main system stack and a rebalancing stack, wherein the two ends of the main system stack are respectively connected to a positive electrode storage tank and a negative electrode storage tank, the positive electrode storage tank is filled with a reducing agent, one end of the rebalancing stack is connected to the positive electrode storage tank, and an adjusting device is provided between the positive electrode storage tank and the positive electrode inlet of the rebalancing stack; The integrated liquid flow battery capacity recovery system also includes a charging and discharging device, which is connected to the main system stack and the rebalancing stack.

2. An integrated liquid flow battery capacity recovery system as claimed in claim 1, characterized in that: The main system stack and the rebalancing stack are connected in parallel, and a DC switch is provided between the main system stack and the rebalancing stack.

3. The integrated liquid flow battery capacity recovery system according to claim 1, characterized in that: The reducing agent includes at least one of formic acid, methanol, ethanol, acetic acid, oxalic acid, hydrogen peroxide, ascorbic acid, hydrazine hydrate, ammonia water and urea.

4. The integrated liquid flow battery capacity recovery system according to claim 1, characterized in that: A positive electrode pump is provided between the positive electrode storage tank and the main system stack and the rebalancing stack, and a negative electrode pump is provided between the negative electrode storage tank and the main system stack.

5. An integrated liquid flow battery capacity recovery system as claimed in claim 4, characterized in that: The positive electrode storage tank is connected with a connecting pipe, one end of the connecting pipe away from the positive electrode storage tank is connected with the negative electrode storage tank, and the negative electrode storage tank is provided with an exhaust pipe.

6. The integrated liquid flow battery capacity recovery system according to claim 1, characterized in that: The regulating device is a regulating valve.

7. The integrated liquid flow battery capacity recovery system according to claim 1, characterized in that: One end of the rebalancing stack away from the positive electrode storage tank is connected to the negative electrode storage tank, and a negative electrode pump is arranged between the negative electrode storage tank and the rebalancing stack.

8. An integrated liquid flow battery capacity recovery system according to claim 1 or 7, characterized in that: A bubbler is arranged inside the positive electrode storage tank, one end of the bubbler is connected to a gas-liquid mixer, and the gas-liquid mixer is connected to the positive electrode outlet of the rebalancing stack and the positive electrode outlet of the main system stack.

9. The integrated liquid flow battery capacity recovery system according to claim 1, characterized in that: The main system stack and the rebalancing stack are combined into a combined stack, which includes a plurality of main system cells and a plurality of rebalancing cells, each of the main system cells includes a main system cell positive electrode, each of the rebalancing cells includes a rebalancing cell positive electrode, and a resistance member is provided in the cell flow channel of the rebalancing cell positive electrode.

10. An integrated liquid flow battery capacity recovery system as claimed in claim 9, characterized in that: The resistance member comprises a screw, one end of which penetrates through the combined battery stack and extends into the battery flow channel of the positive electrode of the rebalancing battery.

11. An integrated liquid flow battery capacity recovery method, based on an integrated liquid flow battery capacity recovery system according to any one of claims 1 to 10, characterized in that: The following steps are involved: The regulating device regulates the flow entering the rebalancing stack so that the voltage reaches the reaction voltage of the reducing agent in the positive electrode storage tank. The electrolyte after the positive electrode reaction of the rebalancing stack flows out from the positive electrode outlet of the rebalancing stack, then flows into the rebalancing stack from the negative electrode inlet of the rebalancing stack, and finally flows out from the negative electrode outlet of the rebalancing stack and returns to the positive electrode storage tank, thereby realizing the capacity recovery of the main system battery.

12. The integrated liquid flow battery capacity recovery method according to claim 11, characterized in that: The products of the positive electrode reaction of the rebalancing stack directly enter the negative electrode of the rebalancing stack, where a reverse reaction occurs and the halogen element gains electrons and turns back into halogen ions, thereby achieving self-circulation of halogen ions in the rebalancing system.

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