A flow battery cycle recovery system and recovery method

Abstract

The present application discloses a liquid flow battery circulation recovery system and recovery method, which belongs to the field of liquid flow battery technology. The recovery system includes a positive electrode storage tank, which is filled with a positive electrode electrolyte. The positive electrode electrolyte contains reducing ions and active ions. The reducing ions can react with the active ions to reduce the valence of the active ions and produce a first oxidizing gas; a catalytic reaction device, which is filled with a catalyst, and the catalytic reaction device can receive the first oxidizing gas to oxidize and fix the catalyst; a negative electrode storage tank, which is filled with a negative electrode electrolyte. The negative electrode electrolyte undergoes a side reaction to produce a first reducing gas; the catalytic reaction device receives the first reducing gas, and the first reducing gas is used to reduce the oxidized catalyst, and the generated acidic gas can return to the negative electrode storage tank. The present application can maintain the valence balance of the positive and negative electrode solutions without adding a recovery agent to the positive electrode solution, avoids contamination of the electrolyte, and realizes long-life stable operation of the liquid flow battery.

Description

Technical Field

[0001] The present application belongs to the technical field of liquid flow batteries, and specifically relates to a liquid flow battery circulation recovery system and recovery method. Background Art

[0002] During the long-term charge and discharge process of the flow battery, the hydrogen evolution side reaction at the negative electrode will cause the average valence of the positive and negative electrode solutions to gradually increase, thereby reducing the capacity of the flow battery. In order to restore the capacity of the flow battery, reducing substances are usually added to the positive electrode solution under high charge state (SOC) conditions. High-valent active ions with strong oxidizing properties can undergo redox reactions with reducing substances to generate low-valent active ions, thereby reducing the average valence of active ions in the positive and negative electrode electrolytes. However, this method will continue to introduce redox reaction residues of the reducing agent.

[0003] Fuel cells can also be constructed using reducing gases and cathode solutions, such as hydrogen, using precious metal catalysts to catalyze the reduction of cathode active substances and reduce their valence. However, since precious metal catalysts easily fall off into the electrolyte, hydrogen evolution at the negative electrode of the flow battery is aggravated, causing the battery capacity to decay rapidly.

[0004] Neither of the above two methods is the optimal choice for flow battery recovery. Summary of the invention

[0005] Purpose of application: This application provides a liquid flow battery circulation recovery system and recovery method, which can realize the capacity recovery of the liquid flow battery without introducing chemical substances to contaminate the electrolyte.

[0006] Technical solution: A flow battery cycle recovery system of the present application includes:

[0007] A positive electrode storage tank, wherein the positive electrode storage tank contains a positive electrode electrolyte, wherein the positive electrode electrolyte contains reducing ions and active ions, wherein the reducing ions can react with the active ions to reduce the valence state of the active ions and generate a first oxidizing gas;

[0008] A catalytic reaction device, wherein the catalytic reaction device contains a catalyst, the catalytic reaction device is connected to the positive electrode liquid storage tank, the catalytic reaction device can receive the first oxidizing gas, and the first oxidizing gas is used to oxidize the catalyst and fix it;

[0009] A negative electrode storage tank is provided with a negative electrode electrolyte, wherein the negative electrode electrolyte contains a supporting electrolyte, and the supporting electrolyte is prone to produce a first reducing gas by a side reaction during or under the charging process of the battery; the negative electrode storage tank is connected to the catalytic reaction device, and the catalytic reaction device can also receive the first reducing gas, and the first reducing gas is used to reduce the catalyst that has been oxidized, and the generated acidic gas can return to the negative electrode storage tank and be absorbed by the negative electrode electrolyte.

[0010] In some embodiments, the positive electrode liquid storage tank includes a first gas outlet and a first gas inlet, the catalytic reaction device includes a second gas inlet and a second gas outlet; the recovery system further includes:

[0011] a first pipeline, the first pipeline being connected to the first gas outlet and the second gas inlet, respectively, and being used to transport the first oxidizing gas from the positive electrode liquid storage tank to the catalytic reaction device;

[0012] A second pipeline, the second pipeline is connected to the second gas outlet and the first gas inlet respectively, and is used to transport the remaining first oxidizing gas from the catalytic reaction device back to the positive electrode liquid storage tank after the catalyst is oxidized.

[0013] In some embodiments, the recovery system further comprises:

[0014] A first one-way guide valve is provided on the first pipeline.

[0015] In some embodiments, it also includes:

[0016] A positive electrode recovery device, the positive electrode recovery device is connected to the positive electrode liquid storage tank, the positive electrode recovery device can receive the positive electrode electrolyte and promote the positive electrode electrolyte reaction to produce a second oxidizing gas;

[0017] The positive electrode recovery device is also connected to the catalytic reaction device, and the catalytic reaction device is capable of receiving the second oxidizing gas, and the second oxidizing gas is used to oxidize the catalyst and fix it.

[0018] In some embodiments, the positive electrode liquid storage tank includes a first liquid outlet and a first liquid inlet, the positive electrode recovery device includes a second liquid inlet and a second liquid outlet, and the recovery system further includes:

[0019] a third pipeline, the third pipeline being connected to the first liquid outlet and the second liquid inlet, respectively, and being used for transporting the positive electrode electrolyte from the positive electrode storage tank to the positive electrode recovery device;

[0020] A fourth pipeline, the fourth pipeline is connected to the second liquid outlet and the first liquid inlet respectively, and is used to transport the reacted positive electrode electrolyte back to the positive electrode storage tank.

[0021] In some embodiments, the positive electrode recovery device further includes a third gas outlet and a third gas inlet; the recovery system further includes:

[0022] a fifth pipeline, the fifth pipeline being connected to the third gas outlet and the second gas inlet, respectively, and being used for transporting the second oxidizing gas from the positive electrode recovery device to the catalytic reaction device;

[0023] A sixth pipeline, the sixth pipeline is connected to the second gas outlet and the third gas inlet, respectively, and is used to transport the remaining second oxidizing gas from the catalytic reaction device back to the positive electrode recovery device after the catalyst is oxidized.

[0024] In some embodiments, the recovery system further comprises:

[0025] A second one-way conducting valve is provided on the fifth pipeline.

[0026] In some embodiments, the negative electrode liquid storage tank includes a fourth gas outlet and a fourth gas inlet, and the recovery system further includes: a seventh pipeline, the seventh pipeline is connected to the fourth gas outlet and the second gas inlet, respectively, and is used to transport the first reducing gas from the negative electrode liquid storage tank to the catalytic reaction device;

[0027] An eighth pipeline, the eighth pipeline is connected to the second gas outlet and the fourth gas inlet, respectively, and is used to transport the gas generated after being oxidized by the catalyst in the catalytic reaction device back to the negative electrode storage tank.

[0028] In some embodiments, the recovery system further comprises:

[0029] A third one-way conducting valve is provided on the seventh pipeline.

[0030] In some embodiments, it also includes:

[0031] a reducing gas source, the reducing gas source being connected to the catalytic reaction device and being used to introduce a second reducing gas into the catalytic reaction device; the catalytic reaction device receiving the second reducing gas, and the second reducing gas being used to reduce the catalyst that has been oxidized;

[0032] An exhaust gas treatment device is connected to the negative electrode liquid storage tank and is used to treat the gas discharged from the negative electrode liquid storage tank.

[0033] In some embodiments, the catalyst is selected from at least one of a copper-based catalyst, a nickel-based catalyst, and a bismuth-based catalyst; or,

[0034] The reducing ions are selected from at least one of chloride ions and bromide ions; or

[0035] The active ions are selected from at least one of vanadium ions, manganese ions, bromide ions, iron ions, and lead ions; or

[0036] The supporting electrolyte is selected from at least one of sulfuric acid, hydrochloric acid and phosphoric acid;

[0037] The first oxidizing gas is selected from at least one of chlorine and bromine;

[0038] The first reducing gas is hydrogen.

[0039] In some embodiments, the second oxidizing gas is selected from at least one of chlorine and bromine; or

[0040] The second reducing gas is selected from at least one of hydrogen, carbon monoxide, methane and propane.

[0041] In some embodiments, the SOC of the positive electrode electrolyte before the reaction is 60% to 100%, and the SOC of the positive electrode electrolyte after the reaction is 50% to 100%.

[0042] In some embodiments, the present application also provides a flow battery cycle recovery method, comprising the following steps:

[0043] The positive electrode storage tank is filled with a positive electrode electrolyte, wherein the positive electrode electrolyte contains reducing ions and active ions, and the reducing ions react with the active ions to reduce the valence of the active ions and generate a first oxidizing gas;

[0044] Passing the first oxidizing gas into a catalytic reaction device, wherein the catalytic reaction device contains a catalyst, and the first oxidizing gas reacts with the catalyst to oxidize and fix the catalyst;

[0045] The negative electrode storage tank is filled with a negative electrode electrolyte, wherein the negative electrode electrolyte contains a supporting electrolyte, and the supporting electrolyte is prone to produce a first reducing gas by a side reaction during or in a charging state of the battery;

[0046] The first reducing gas is introduced into the catalytic reaction device, and a redox reaction occurs between the first reducing gas and the oxidized catalyst. The catalyst is reduced and releases acidic gas. The generated acidic gas can return to the negative electrode storage tank and be absorbed by the negative electrode electrolyte.

[0047] In some embodiments, the molar ratio of the reducing ions to the active ions is (1-10): (0.1-5);

[0048] Wherein, the concentration of the reducing ions in the positive electrode electrolyte is 0.5-10 mol / L;

[0049] The concentration of the active ions in the positive electrode electrolyte is 0.1-5 mol / L.

[0050] The concentration of the supporting electrolyte in the negative electrode electrolyte is 0.5-10 mol / L.

[0051] In some embodiments, the temperature at which the reducing ions react with the active ions is 20-100° C.; or

[0052] The temperature at which the first oxidizing gas reacts with the catalyst is 20-400° C.; or

[0053] The reaction temperature of the first reducing gas and the oxidized catalyst is 100-550° C.; or in some embodiments, before the step of reacting the reducing ions with the active ions, the step further includes:

[0054] Passing the positive electrode electrolyte into the positive electrode recovery device, adjusting the temperature to make the positive electrode electrolyte react to generate a second oxidizing gas and reduce the valence of the active ions;

[0055] A second oxidizing gas is introduced into the catalytic reaction device, and the second oxidizing gas reacts with the catalyst to oxidize the catalyst.

[0056] In some embodiments, in the positive electrode recovery device, the temperature is adjusted in the range of 20-100°C.

[0057] In some embodiments, before the step of reacting the first oxidizing gas with the catalyst and / or after the step of reacting the first reducing gas with the oxidized catalyst,

[0058] Passing a second reducing gas provided by a reducing gas source into the catalytic reaction device, and reacting the first reducing gas with at least a portion of the oxidized catalyst to completely reduce the catalyst;

[0059] The gas after the reaction is introduced into the negative electrode storage tank, and then processed and discharged through the exhaust gas treatment device.

[0060] Beneficial effect: Compared with the prior art, a liquid flow battery circulation recovery system of the present application includes: a positive electrode storage tank, the positive electrode storage tank is filled with a positive electrode electrolyte, the positive electrode electrolyte contains reducing ions and active ions, the reducing ions can react with the active ions to reduce the valence state of the active ions and produce a first oxidizing gas; a catalytic reaction device, the catalytic reaction device is filled with a catalyst, the catalytic reaction device is connected to the positive electrode storage tank, the catalytic reaction device can receive the first oxidizing gas, and the first oxidizing gas is used to oxidize the catalyst; a negative electrode storage tank, the negative electrode storage tank is filled with a negative electrode electrolyte, the negative electrode electrolyte contains a supporting electrolyte, and the supporting electrolyte is prone to side reactions during or under battery charging to produce a first reducing gas; the negative electrode storage tank is connected to the catalytic reaction device, the catalytic reaction device can also receive the first reducing gas, and the first reducing gas is used to reduce the catalyst that has been oxidized. The present application relates to a liquid flow battery circulation recovery system, which can maintain the valence state balance of the positive and negative electrode solutions without adding a recovery agent to the positive electrode solution, thereby avoiding electrolyte contamination and realizing the application of long-life, non-attenuation liquid flow batteries. The present application relates to a liquid flow battery circulation recovery system, which also introduces an auxiliary reduction gas source to achieve full reduction of the catalyst and achieve the cyclic application of the catalyst.

[0061] The liquid flow battery circulation recovery system of the present application also includes a positive electrode recovery device, which is connected to the positive electrode storage tank, and can receive the positive electrode electrolyte and promote the positive electrode electrolyte reaction to produce a second oxidizing gas; the positive electrode recovery device is also connected to the catalytic reaction device, and the catalytic reaction device can receive the second oxidizing gas, and the second oxidizing gas is used to oxidize the catalyst. The positive electrode recovery device can promote the reaction of the positive electrode electrolyte and produce the second oxidizing gas; the produced second oxidizing gas can react with the catalyst, thereby reducing the valence of the active ions in the positive electrode electrolyte, helping to achieve the purpose of restoring the battery capacity.

[0062] A liquid flow battery cycle recovery method of the present application includes the following steps: a positive electrode electrolyte is contained in a positive electrode storage tank, the positive electrode electrolyte contains reducing ions and active ions, the reducing ions react with the active ions to reduce the valence state of the active ions and generate a first oxidizing gas; the first oxidizing gas is passed into a catalytic reaction device, the catalytic reaction device is contained in the catalyst, the first oxidizing gas reacts with the catalyst to oxidize the catalyst; a negative electrode electrolyte is contained in a negative electrode storage tank, the negative electrode electrolyte contains a supporting electrolyte, the supporting electrolyte is prone to side reactions to generate the first reducing gas during the battery charging process or state; the first reducing gas is passed into the catalytic reaction device, the first reducing gas undergoes a redox reaction with the oxidized catalyst, the catalyst is reduced and releases an acidic gas, and the generated acidic gas can return to the negative electrode storage tank and be absorbed by the negative electrode electrolyte. The method of the present application links the recovery process with the attenuation of the flow battery capacity and the SOC, thereby realizing automatic operation of the flow battery recovery; and the method of the present application can also be configured with an optional recovery system of an external reducing gas source, so that external intervention adjustment of the electrolyte can be performed according to actual operating conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0063] The technical solution and other beneficial effects of the present application will be made apparent by describing in detail the specific implementation methods of the present application in conjunction with the accompanying drawings.

[0064] Figure 1 A connection diagram of a flow battery circulation recovery system provided in an embodiment of the present application;

[0065] Figure 2 A schematic diagram of the connection of the positive electrode recovery device provided in the embodiment of the present application;

[0066] Figure 3 A schematic diagram of the connection of a reducing gas source provided in an embodiment of the present application;

[0067] Figure 4 Schematic diagram of the structure of a flow battery;

[0068] Figure 5 A flow chart of a flow battery cycle recovery method provided in an embodiment of the present application;

[0069] Figure 6 A comparison chart of the catalyst provided in the embodiment of the present application before and after chlorine oxidation and before and after hydrogen reduction;

[0070] Reference numerals: 10-positive electrode liquid storage tank, 101-first gas outlet, 102-first gas inlet, 103-first liquid outlet, 104-first liquid inlet, 20-catalytic reaction device, 201-second gas inlet, 202-second gas outlet, 30-negative electrode liquid storage tank, 301-fourth gas outlet, 302-fourth gas inlet, 40-first pipeline, 401-first one-way valve, 50-second pipeline, 60 - positive electrode recovery device, 601- second liquid inlet end, 602- second liquid outlet end, 603- third gas outlet end, 604- third gas inlet end, 70- third pipeline, 80- fourth pipeline, 90- fifth pipeline, 901- second one-way guide valve, 100- sixth pipeline, 200- seventh pipeline, 2001- third one-way guide valve, 300- eighth pipeline, 400- reduction gas source, 500- tail gas treatment device. DETAILED DESCRIPTION

[0071] The technical solutions in the embodiments of the present application will be described clearly and completely below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present application.

[0072] In the description of the present application, it should be noted that, unless otherwise clearly specified and limited, the terms "connected" and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection, an electrical connection, or can communicate with each other; it can be directly connected, or indirectly connected through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to the specific circumstances. In the description of the present application, the meaning of "multiple" is two or more, unless otherwise clearly and specifically defined. In addition, the terms "first" and "second" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more features.

[0073] In the present example, the reagents or instruments used without indicating the manufacturer are all conventional products that can be obtained through commercial purchase.

[0074] The disclosure below provides many different embodiments or examples to realize the different structures of the present application. In order to simplify the disclosure of the present application, the parts and settings of specific examples are described below. Of course, they are only examples, and the purpose is not to limit the present application.

[0075] The applicant discovered that the liquid flow battery is an electrochemical energy storage technology proposed by Thaller and is a new type of storage battery. The liquid flow battery is composed of a battery stack unit, an electrolyte, an electrolyte storage and supply unit, and a management and control unit. It is a high-performance storage battery that separates the positive and negative electrolytes and circulates them separately. It has the characteristics of high capacity, wide application field (environment), and long cycle life. As a new type of large-scale and efficient electrochemical energy storage (electricity) technology, liquid flow battery technology realizes the mutual conversion and energy storage of electrical energy and chemical energy through the valence change of reactive substances. The structural schematic diagram of the liquid flow battery is shown in the figure below. Figure 4 As shown in the figure, the positive and negative electrolytes of the battery are respectively stored in two tanks, and the electrolytes are circulated in the battery system by a liquid delivery pump. Inside the battery stack, the positive and negative electrolytes are separated by an ion exchange membrane (or ion diaphragm), and the battery is connected to an external load and power supply; during the charge and discharge process, the positive and negative electrolytes realize the redox reaction of the corresponding electrodes on the electrodes in the battery stack; with the continuous charge and discharge cycle, the charge and discharge capacity of the flow battery will inevitably decay to varying degrees.

[0076] Taking vanadium-containing liquid flow batteries as an example, the increase in the average valence of vanadium ions in the positive and negative electrolytes caused by the hydrogen evolution reaction at the negative electrode is one of the important reasons for the capacity decay of liquid flow batteries. ,negative electrode In the initial stage, the amount of active substances in the positive and negative electrodes is equal. During the cycle, the negative electrode electrolyte continues to undergo hydrogen evolution reaction:

[0077] ;

[0078] This causes the valence state of vanadium ions to continue to increase, which is manifested as a gradual increase in the concentration of pentavalent vanadium in the positive electrode solution at the end of the discharge step, directly leading to a gradual decay of the battery capacity.

[0079] In order to restore the capacity of the battery, reducing substances are usually added to the cathode solution under high SOC conditions. High-valent active ions with strong oxidizing properties can undergo redox reactions with reducing substances to generate low-valent active ions, thereby reducing the average valence state of the active ions in the positive and negative electrolytes. This method will continuously introduce redox reaction residues of the reducing agent. On the other hand, the fuel cell method is also one of the current research and application directions. The battery is constructed with reducing gas and cathode solution, and precious metal catalysts are used to catalyze the reduction of the cathode active substance to reduce the valence state. However, since the precious metal catalysts are easily detached and enter the electrolyte, hydrogen evolution at the negative electrode is aggravated, causing the battery capacity to decay rapidly.

[0080] Therefore, there is an urgent need for a recovery method for flow batteries that can restore the battery capacity without introducing chemical substances to contaminate the electrolyte.

[0081] Based on the above problems, see Figure 1 The embodiment of the present application provides a flow battery circulation recovery system, including: a positive electrode storage tank 10, a catalytic reaction device 20 and a negative electrode storage tank 30, the positive electrode storage tank 10 is filled with a positive electrode electrolyte, the positive electrode electrolyte contains reducing ions and active ions, the reducing ions can react with the active ions to reduce the valence state of the active ions and produce a first oxidizing gas; the catalytic reaction device 20 is filled with a catalyst, the catalytic reaction device 20 is connected to the positive electrode storage tank 10, the catalytic reaction device 20 can receive the first oxidizing gas, and the first oxidizing gas is used to oxidize the catalyst; the negative electrode storage tank 30 is filled with a negative electrode electrolyte, the negative electrode electrolyte contains a supporting electrolyte, and the supporting electrolyte is prone to side reactions during or under battery charging to produce a first reducing gas; the negative electrode storage tank 30 is connected to the catalytic reaction device 20, the catalytic reaction device 20 can also receive the first reducing gas, and the first reducing gas is used to reduce the oxidized catalyst, so that the generated acidic gas can return to the negative electrode storage tank 30 and be absorbed by the negative electrode electrolyte.

[0082] The all-vanadium liquid flow battery consists of two reaction pairs, positive and negative. During the charging process, an oxidation reaction occurs at the positive electrode and a reduction reaction occurs at the negative electrode:

[0083] Positive electrode reaction: VO 2+ +H2O=e - +VO2 + +2H + ; (1V)

[0084] Negative electrode reaction: V 3+ + e - =V 2+ ; (-0.225V)

[0085] During the discharge process, a reduction reaction occurs at the positive electrode and an oxidation reaction occurs at the negative electrode, which is the opposite of the above reaction.

[0086] Setting active ions of the same mass at the positive and negative electrodes of the battery can theoretically enable the battery to achieve charge and discharge capabilities, that is, in the initial state of charging, when the mass of the tetravalent vanadium ions in the positive electrode electrolyte is the same as the mass of the trivalent vanadium in the negative electrode electrolyte, the positive and negative electrodes can charge the same number of electrons, or in the initial state of discharging, when the mass of the pentavalent vanadium ions in the positive electrode is the same as the mass of the divalent vanadium ions in the negative electrode, the positive and negative electrodes can release the same number of electrons in the electrochemical reaction. The capacity of the battery depends on the minimum of the two, that is, in the initial state of charging, the lowest mass of the tetravalent vanadium ions in the positive electrode electrolyte and the trivalent vanadium in the negative electrode electrolyte determines the chargeable capacity; in the initial state of discharging, the lowest mass of the pentavalent vanadium ions in the positive electrode and the divalent vanadium ions in the negative electrode determines the dischargeable capacity.

[0087] At the negative electrode of the battery, hydrogen reduction reaction is likely to occur:

[0088] 2H + +2e - =H2; (0V)

[0089] The potential of divalent and trivalent vanadium at the negative electrode is lower than the standard potential of the hydrogen evolution reaction (HER). However, since carbon felt is used as an electrode in the battery, its hydrogen evolution overpotential is relatively high, so the occurrence of the hydrogen evolution reaction can be suppressed to a large extent. However, the hydrogen evolution reaction cannot be completely suppressed, and the hydrogen evolution reaction is irreversible. When the hydrogen evolution reaction occurs, the corresponding reaction at the positive electrode is the oxidation of vanadium. As the battery charge and discharge process cycles, the amount of hydrogen evolution gradually accumulates, the total amount of tetravalent vanadium contained in the positive electrode electrolyte becomes lower and lower, and the battery charge capacity gradually decreases.

[0090] It can be understood that in order to restore the capacity of the battery, in the system of this embodiment, the reaction of the positive electrode electrolyte in the positive electrode storage tank 10 is used to reduce the valence of the active ions and generate the first oxidizing gas, specifically to reduce the pentavalent vanadium to a tetravalent state, thereby increasing the total amount of tetravalent vanadium in the positive electrode so that it is close to the mass of trivalent vanadium in the negative electrode at the initial stage of charging, thereby realizing the recovery of the battery capacity. Figure 1 In some embodiments, the recovery system of the present application is a self-circulating closed system. The entire process does not introduce any additional devices or gas sources, and does not require any external recovery agents, which can ensure the recovery of battery capacity and avoid electrolyte contamination.

[0091] In some embodiments, see further Figure 1 , the positive electrode liquid storage tank 10 includes a first gas outlet 101 and a first gas inlet 102, and the catalytic reaction device 20 includes a second gas inlet 201 and a second gas outlet 202; the recovery system also includes: a first pipeline 40 and a second pipeline 50, the first pipeline 40 is connected to the first gas outlet 101 and the second gas inlet 201 respectively, and is used to transport the first oxidizing gas from the positive electrode liquid storage tank 10 to the catalytic reaction device 20; the second pipeline 50 is connected to the second gas outlet 202 and the first gas inlet 102 respectively, and is used to transport the remaining first oxidizing gas from the catalytic reaction device 20 back to the positive electrode liquid storage tank 10 after the catalyst is oxidized. It can be understood that the arrangement of the first pipeline 40 and the second pipeline 50 realizes the cyclic transportation of the first oxidizing gas, and the first oxidizing gas is transported from the positive electrode liquid storage tank 10 to the catalytic reaction device 20 through the first pipeline 40, and then transported back to the positive electrode liquid storage tank 10 again through the second pipeline 50. This cyclic transportation ensures full utilization of the gas. The balance of active ions and reducing ions in the positive and negative electrode electrolytes can be maintained, which helps to avoid the problem of high average valence of the positive and negative electrode electrolytes caused by side reactions such as hydrogen evolution in traditional liquid flow batteries, thereby reducing the impact of battery capacity decay.

[0092] In some embodiments, see further Figure 1The recovery system further includes a first one-way valve 401, which is disposed on the first pipeline 40. The first one-way valve 401 allows the first oxidizing gas to flow out of the positive electrode liquid storage tank 10 only, but not flow back to the positive electrode liquid storage tank 10.

[0093] In some embodiments, see further Figure 2 The recovery system also includes a positive electrode recovery device 60, which is connected to the positive electrode storage tank 10. The positive electrode recovery device 60 can receive the positive electrode electrolyte and promote the reaction of the positive electrode electrolyte to produce a second oxidizing gas; the positive electrode recovery device 60 is also connected to the catalytic reaction device 20, which can receive the second oxidizing gas, and the second oxidizing gas is used to oxidize the catalyst.

[0094] It should be noted that the positive electrode recovery device 60 is a device that promotes the reaction of the positive electrode electrolyte, reduces the active substances in the positive electrode electrolyte, and produces a second oxidizing gas; the second oxidizing gas can be any one of chlorine and bromine. When the reaction rate of the reducing ions in the positive electrode electrolyte and the high-valent active ions is too slow or the valence of the active ions in the electrolyte needs to be greatly reduced, the positive electrode recovery device 60 needs to be connected; the high SOC positive electrode electrolyte is pumped into the positive electrode recovery device, and the temperature is adjusted to achieve the redox reaction of the reducing ions and the active high-valent ions to produce a second oxidizing gas, thereby reducing the valence of the active ions in the positive electrode electrolyte and achieving the purpose of restoring the battery capacity.

[0095] In some embodiments, see further Figure 2 , the positive electrode storage tank 10 includes a first liquid outlet 103 and a first liquid inlet 104, the positive electrode recovery device 60 includes a second liquid inlet 601 and a second liquid outlet 602, and the recovery system further includes: a third pipeline 70 and a fourth pipeline 80, the third pipeline 70 is connected to the first liquid outlet 103 and the second liquid inlet 601, respectively, for transporting the positive electrode electrolyte from the positive electrode storage tank 10 to the positive electrode recovery device 60; the fourth pipeline 80 is connected to the second liquid outlet 602 and the first liquid inlet 104, respectively, for transporting the reacted positive electrode electrolyte back to the positive electrode storage tank 10. It can be understood that the third pipeline 70 and the fourth pipeline 80 are used to pump out the positive electrode electrolyte with a high SOC from the positive electrode storage tank 10 and introduce it into the positive electrode recovery device 60 for reaction recovery, and then return it to the positive electrode storage tank 10.

[0096] In some embodiments, see further Figure 2, the positive electrode recovery device 60 also includes a third gas outlet 603 and a third gas inlet 604; the recovery system also includes: a fifth pipeline 90 and a sixth pipeline 100, the fifth pipeline 90 is connected to the third gas outlet 603 and the second gas inlet 201 respectively, and is used to transport the second oxidizing gas from the positive electrode recovery device 60 to the catalytic reaction device 20; the sixth pipeline 100 is connected to the second gas outlet 202 and the third gas inlet 604 respectively, and is used to transport the remaining second oxidizing gas from the catalytic reaction device 20 back to the positive electrode recovery device 60 after the catalyst is oxidized. The arrangement of the fifth pipeline 90 and the sixth pipeline 100 can maintain the balance of active ions and reducing ions in the positive and negative electrode electrolytes, which helps to avoid the problem of high average valence of the positive and negative electrode electrolytes caused by side reactions such as hydrogen evolution in traditional liquid flow batteries, thereby reducing the impact of battery capacity decay.

[0097] In some embodiments, see Figure 2 The recovery system further includes: a second one-way valve 901, which is disposed on the fifth pipeline 90. The second one-way valve 901 allows the first oxidizing gas to flow out of the positive electrode recovery device 60 and prevents the first reducing gas from flowing into the positive electrode recovery device 60.

[0098] In some embodiments, see further Figure 1 , the negative electrode liquid storage tank 30 includes a fourth gas outlet 301 and a fourth gas inlet 302, and the recovery system also includes: a seventh pipeline 200 and an eighth pipeline 300, the seventh pipeline 200 is connected to the fourth gas outlet 301 and the second gas inlet 201 respectively, and is used to transport the first reducing gas from the negative electrode liquid storage tank 30 to the catalytic reaction device 20; the eighth pipeline 300 is connected to the second gas outlet 202 and the fourth gas inlet 302 respectively, and is used to transport the gas generated by the catalyst oxidation in the catalytic reaction device 20 back to the negative electrode liquid storage tank 30. It should be noted that the seventh pipeline 200 and the eighth pipeline 300 realize the circulation of the first reducing gas and the gas generated by the catalyst oxidation in the catalytic reaction device 20.

[0099] In some embodiments, the recovery system further includes a third one-way valve 2001, which is disposed on the seventh pipeline 200. The third one-way valve 2001 allows the first reducing gas to flow out of the negative electrode liquid storage tank 30, and prevents the first oxidizing gas and the second oxidizing gas from flowing into the negative electrode liquid storage tank 30.

[0100] In some embodiments, see Figure 3The recovery system further includes: a reducing gas source 400 and an exhaust gas treatment device 500, wherein the reducing gas source 400 is connected to the catalytic reaction device 20 for introducing a second reducing gas into the catalytic reaction device 20; the catalytic reaction device 20 receives the second reducing gas, and the second reducing gas is used to reduce the oxidized catalyst; the exhaust gas treatment device 500 is connected to the negative electrode storage tank 30 for treating the gas discharged from the negative electrode storage tank 30. It is understandable that the setting of the reducing gas source 400 can further provide the catalytic reaction device 20 with a second reducing gas, which can ensure that the catalyst in the catalytic reaction device 20 is completely reduced, and maximize the amount of the catalyst reacting with the first oxidizing gas and the second oxidizing gas. The exhaust gas treatment device 500 can ensure that the gas discharged from the negative electrode storage tank 30 is discharged after producing water or carbon dioxide through catalytic oxidation, thereby avoiding environmental pollution.

[0101] In some embodiments, the catalyst is selected from at least one of a copper-based catalyst, a nickel-based catalyst, and a bismuth-based catalyst. Copper-based catalysts include, but are not limited to, copper, copper oxide, copper chloride, cuprous chloride, copper bromide, copper iodide, and copper-containing alloys; nickel-based catalysts include, but are not limited to, nickel, nickel oxide, nickel chloride, nickel bromide, and nickel-containing alloys; bismuth-based catalysts include, but are not limited to, bismuth, bismuth oxide, bismuth chloride, bismuth bromide, and bismuth-containing alloys.

[0102] In some embodiments, the reduced state of the catalyst can be judged by color appearance, such as metallic luster. Figure 6 , the catalyst is in a light-colored state before oxidation, in a dark-colored state after oxidation, and returns to a light-colored state after reduction.

[0103] In some embodiments, the reducing ion is selected from at least one of chloride ion and bromide ion.

[0104] In some embodiments, the reducing ions are provided by a component that can release chloride ions or bromide ions, such as one or a mixture of perchloric acid, hypochlorous acid, chloric acid, hydrochloric acid, liquid bromine, hypobromous acid, hydrobromic acid and bromic acid.

[0105] In some embodiments, the active ions are selected from at least one of vanadium ions, manganese ions, bromide ions, iron ions, and lead ions.

[0106] In some embodiments, the negative electrode electrolyte contains one or a mixture of vanadium ions, chromium ions, manganese ions, titanium ions, iron ions, zinc ions, tin ions, bismuth ions, and mercury ions.

[0107] In some embodiments, the supporting electrolyte is selected from at least one of sulfuric acid, hydrochloric acid, and phosphoric acid.

[0108] In some embodiments, the first oxidizing gas is selected from at least one of chlorine and bromine.

[0109] In some embodiments, the first reducing gas is hydrogen.

[0110] In some embodiments, the second oxidizing gas is selected from at least one of chlorine and bromine.

[0111] In some embodiments, the second reducing gas is selected from at least one of hydrogen, carbon monoxide, methane, and propane.

[0112] In some embodiments, the SOC of the positive electrolyte before the reaction is 60% to 100%, and the SOC of the positive electrolyte after the reaction is 50% to 100%. Preferably, the SOC of the positive electrolyte before the reaction is 75% to 90%, and the SOC of the positive electrolyte after the reaction is 60% to 70%. Among them, SOC (State of Charge) represents the charge state of the battery, which indicates the ratio between the amount of charge currently stored in the battery and its maximum charge capacity.

[0113] In some embodiments, see Figure 5 , and also provides a flow battery cycle recovery method, comprising the following steps:

[0114] A positive electrode electrolyte is introduced into the positive electrode storage tank 10. The positive electrode electrolyte contains reducing ions and active ions. The reducing ions react with the active ions to reduce the valence of the active ions and generate a first oxidizing gas.

[0115] The first oxidizing gas is introduced into the catalytic reaction device 20, in which a catalyst is installed, and the first oxidizing gas reacts with the catalyst to oxidize the catalyst;

[0116] A negative electrode electrolyte is introduced into the negative electrode storage tank 30, wherein the negative electrode electrolyte contains a supporting electrolyte, and the supporting electrolyte is prone to produce a first reducing gas by a side reaction during or in a state of battery charging;

[0117] The first reducing gas is introduced into the catalytic reaction device 20, and the first reducing gas undergoes a redox reaction with the oxidized catalyst, the catalyst is reduced and releases acidic gas, and the generated acidic gas can return to the negative electrode storage tank 30 and be absorbed by the negative electrode electrolyte.

[0118] It can be understood that the method of the present application links the recovery process with the attenuation of battery capacity and SOC, thereby realizing automatic operation of battery recovery. The liquid flow battery circulation recovery system solves the problem of battery capacity attenuation caused by the high average valence state of the positive and negative electrode electrolytes due to side reactions such as hydrogen evolution in the liquid flow battery.

[0119] In some embodiments, the molar ratio of reducing ions to active ions is (1-10): (0.1-5). Further preferably, the molar ratio of reducing ions to active ions can be any one of 1:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1 or a range between any two of the ratios.

[0120] In some embodiments, the concentration of reducing ions in the positive electrode electrolyte is 0.5~10 mol / L; for example, it can be any one of 0.5 mol / L, 0.6 mol / L, 0.7 mol / L, 0.8 mol / L, 0.9 mol / L, 1 mol / L, 2 mol / L, 3 mol / L, 4 mol / L, 5 mol / L, 6 mol / L, 7 mol / L, 8 mol / L, 9 mol / L, 10 mol / L, or a range between any two values.

[0121] In some embodiments, the concentration of active ions in the positive electrode electrolyte is 0.1 to 5 mol / L. For example, it can be any one of 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, 0.4 mol / L, 0.5 mol / L, 0.6 mol / L, 0.7 mol / L, 0.8 mol / L, 0.9 mol / L, 1 mol / L, 2 mol / L, 3 mol / L, 4 mol / L, 5 mol / L, or a range between any two values.

[0122] In some embodiments, the concentration of the supporting electrolyte in the negative electrode electrolyte is 0.5 to 10 mol / L. For example, it can be any one of 0.5 mol / L, 0.6 mol / L, 0.7 mol / L, 0.8 mol / L, 0.9 mol / L, 1 mol / L, 2 mol / L, 3 mol / L, 4 mol / L, 5 mol / L, 6 mol / L, 7 mol / L, 8 mol / L, 9 mol / L, and 10 mol / L, or a range between any two values.

[0123] In some embodiments, the temperature at which the reducing ions react with the active ions is 20-100° C. For example, it can be any one of 20° C., 30° C., 40° C., 50° C., 60° C., 70° C., 80° C., 90° C., and 100° C., or a range between any two of the values.

[0124] In some embodiments, the temperature at which the first oxidizing gas reacts with the catalyst is 20-400°C; for example, it can be any one of 20°C, 50°C, 100°C, 120°C, 150°C, 180°C, 200°C, 250°C, 300°C, 350°C, 400°C, or a range between any two values.

[0125] In some embodiments, the reaction temperature of the first reducing gas and the oxidized catalyst is 100~550°C; for example, it can be any one of 100°C, 150°C, 200°C, 250°C, 300°C, 350°C, 400°C, 450°C, 500°C, 550°C or a range between any two values.

[0126] In some embodiments, before the step of reacting the reducing ions with the active ions, the method further comprises:

[0127] Passing the positive electrode electrolyte into the positive electrode recovery device 60, adjusting the temperature to make the positive electrode electrolyte react to generate a second oxidizing gas and reduce the valence of active ions;

[0128] The second oxidizing gas is introduced into the catalytic reaction device 20, and the second oxidizing gas reacts with the catalyst to oxidize the catalyst.

[0129] It is understandable that the positive electrode recovery device 60 can further enhance the reaction between the reducing ions and the active ions in the positive electrode electrolyte to ensure the generation of the second oxidizing gas, thereby reducing the valence state of the active ions in the positive electrode electrolyte and achieving the purpose of restoring the battery capacity. The second oxidizing gas and the first oxidizing gas are the same gas and can be used to generate an oxidation reaction with the catalyst.

[0130] In some embodiments, in the positive electrode recovery device 60, the temperature is adjusted in the range of 20-100° C. For example, the adjusted temperature can be any one of 20° C., 25° C., 30° C., 35° C., 40° C., 45° C., 50° C., 55° C., 60° C., 65° C., 70° C., 75° C., 80° C., 85° C., 90° C., 95° C., and 100° C., or a range between any two values.

[0131] In some embodiments, before the step of reacting the first oxidizing gas with the catalyst and / or after the step of reacting the first reducing gas with the oxidized catalyst, when the amount of the first reducing gas is insufficient, the catalyst cannot be completely reduced.

[0132] Passing the second reducing gas provided by the reducing gas source 400 into the catalytic reaction device 20 to completely reduce the catalyst;

[0133] The reacted gas is introduced into the negative electrode liquid storage tank 30, and then is processed by the tail gas treatment device 500 and discharged.

[0134] It is understandable that, in addition to the liquid flow battery circulation recovery system, an optional recovery system of an external reducing gas source 400 is configured, which can perform external intervention adjustments of the electrolyte according to actual operating conditions.

[0135] Using the above-mentioned liquid flow battery cycle recovery method, the battery's charge and discharge cycle capacity has almost no attenuation, truly achieving the characteristics of a long-life, attenuation-free liquid flow battery.

[0136] Specifically provided is a recovery method for a flow battery, comprising:

[0137] Step 1: Load the catalyst into the catalytic reaction device 20, connect the catalytic reaction device 20 to the reducing gas source 400 in a circular manner, and introduce the second reducing gas into the catalyst in the catalytic reaction device 20 for pre-reduction; taking nickel oxide as an example, the following reaction occurs:

[0138] NiO(s)+CO(g)=Ni(s)+CO2(g);

[0139] The gas generated after the reaction is introduced into the negative electrode liquid storage tank through the external circulation pipeline, and then discharged after passing through the tail gas treatment device 500; after the reaction is completed, step 2 is entered; if a reducing catalyst is used, step 2 is directly entered;

[0140] Step 2: Under high SOC, the reducing ions in the positive electrode storage tank 10 react with the high-valent active ions to generate the first oxidizing gas, and the reaction is as follows:

[0141] ;

[0142] Step 3: Switch the internal circulation pipeline, pump the first oxidizing gas into the catalytic reaction device 20 through the first pipeline 40, take the nickel catalyst as an example, the catalytic reaction device 20 undergoes an absorption reaction to generate nickel chloride; the residual gas returns to the positive electrode storage tank 10 through the second pipeline 50 to achieve cyclic absorption;

[0143] Step 4: Switch the circulation pipeline, pump the first reducing gas generated in the negative electrode storage tank 30 into the catalytic reaction device 20 through the seventh pipeline 200 to reduce the catalyst; taking nickel chloride as an example, the reaction that occurs is as follows:

[0144] NiCl2(s)+H2(g) = Ni(s)+2HCl(g);

[0145] The gas (hydrogen chloride) generated in the catalytic reaction device 20 is passed into the negative electrode liquid storage tank 30 via the eighth pipeline 300; the catalyst is reduced to the target state within a certain circulation volume, and returns to step 2 to achieve internal circulation, otherwise it goes to step 5;

[0146] Step 5, switch the circulation pipeline, introduce external reducing gas (H2) to reduce the catalyst, and the reaction is the same as step 4; when the catalyst is reduced to the target state, return to step 2;

[0147] Step 6: When the reaction speed of the reducing ions and high-valent active ions in the positive electrode electrolyte is too slow or the valence of the active ions in the positive electrode electrolyte needs to be greatly reduced, the positive electrode recovery device 60 is connected; the high SOC positive electrode electrolyte is pumped into the positive electrode recovery device 60 through the third pipeline 70, and the temperature is adjusted to achieve the redox reaction of the reducing ions and the active high-valent ions to generate halogen gas (such as chlorine), thereby reducing the valence of the active ions in the positive electrode electrolyte and achieving the purpose of restoring the battery capacity. The reaction is the same as step 2; the positive electrode electrolyte after the reaction is then transported back to the positive electrode storage tank 10 through the fourth pipeline 80;

[0148] Step 7: pump the gas (containing halogen gas) in the positive electrode recovery device 60 into the catalytic reaction device 20 through the fifth pipeline 90, and the reaction is the same as step 3; the residual gas is pumped into the positive electrode recovery device 60 through the sixth pipeline 100 to achieve cyclic absorption; then enter step 4 or step 5 again.

[0149] In the above recovery method, the liquid circulation mode of the positive electrode electrolyte recovery is: positive electrode liquid storage tank-positive electrode recovery device-positive electrode liquid storage tank.

[0150] In the above recovery method, the circulation mode of the gas oxidation catalyst includes: 1) positive electrode liquid storage tank-catalytic reaction device-positive electrode liquid storage tank; 2) positive electrode recovery device-catalytic reaction device-positive electrode recovery device;

[0151] In the above recovery method, the circulation mode of the gas reduction catalyst includes: 1) negative electrode liquid storage tank-gas device-negative electrode liquid storage tank; 2) reducing gas source-catalytic reaction device-negative electrode liquid storage tank-exhaust gas treatment device.

[0152] Specific applications

[0153] As shown in Table 1, the initial average valence of vanadium ions in the positive and negative electrolytes of the flow battery is 3.503, and the single-side capacities of the positive and negative electrolytes are: 15894.83 Ah for the positive electrode and 15964.52 Ah for the negative electrode, respectively. The theoretical maximum capacity of the battery is: 15894.83 Ah; the initial concentration of pentavalent vanadium in the positive electrode is: 0.069 mol / L. After 100 charge and discharge cycles, the average valence of vanadium ions in the positive and negative electrodes increased from the initial 3.503 to 3.601, and the single-side capacities of the positive and negative electrolytes were: 14054.07 Ah for the positive electrode and 16800.69 Ah for the negative electrode, respectively. The theoretical maximum capacity of the battery dropped to 14054.07 Ah. After 100 cycles, the flow battery was charged to a high SOC state, and the flow battery circulation recovery system provided in the embodiment of the present application was used to adjust the valence state. The temperature of the catalytic reaction device was adjusted to 100° C., and chlorine gas in the positive electrode storage tank was circulated until the catalyst surface turned black-gray. After the catalytic reaction device was adjusted to 450° C., hydrogen produced by the hydrogen evolution reaction in the negative electrode storage tank was circulated for 60 minutes, and then the external reducing gas was switched until the color of the catalyst turned silver-gray.

[0154] Table 1

[0155]

[0156] The results of the segmented sampling test are shown in Table 1. After the first recovery cycle procedure, the positive electrode SOC decreased from the original 88.81% to 73.17%, the average valence of vanadium ions recovered to 3.495, and the theoretical maximum capacity recovered to 16119.37 Ah. The three cycles of charge and discharge test recovery cycles were completed, and the results showed that the theoretical maximum capacity was restored to 15964.52 Ah. Therefore, the recovery system of the present application can well maintain the battery capacity.

[0157] The above is a detailed introduction to a liquid flow battery circulation recovery system and recovery method provided in the embodiments of the present application. Specific examples are used in the present application to illustrate the principles and implementation methods of the present application. The description of the above embodiments is only used to help understand the technical solution and its core idea of ​​the present application. Ordinary technicians in this field should understand that they can still modify the technical solutions recorded in the aforementioned embodiments, or replace some of the technical features therein with equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A flow battery cycle recovery system, characterized in that: include: A positive electrode storage tank, wherein the positive electrode storage tank contains a positive electrode electrolyte, wherein the positive electrode electrolyte contains reducing ions and active ions, wherein the reducing ions can react with the active ions to reduce the valence state of the active ions and generate a first oxidizing gas; A catalytic reaction device, wherein the catalytic reaction device contains a catalyst, the catalytic reaction device is connected to the positive electrode liquid storage tank, the catalytic reaction device can receive the first oxidizing gas, and the first oxidizing gas is used to oxidize the catalyst and fix it; A negative electrode liquid storage tank, wherein the negative electrode liquid storage tank contains a negative electrode electrolyte, the negative electrode electrolyte contains a supporting electrolyte, and the supporting electrolyte undergoes a side reaction to generate a first reducing gas; the negative electrode liquid storage tank is connected to the catalytic reaction device, the catalytic reaction device can also receive the first reducing gas, and the first reducing gas is used to reduce the oxidized catalyst, and the generated acidic gas can return to the negative electrode liquid storage tank and be absorbed by the negative electrode electrolyte; Wherein, the positive electrode liquid storage tank includes a first gas outlet and a first gas inlet, and the catalytic reaction device includes a second gas inlet and a second gas outlet; the recovery system also includes: a first pipeline, the first pipeline being connected to the first gas outlet and the second gas inlet, respectively, and being used to transport the first oxidizing gas from the positive electrode liquid storage tank to the catalytic reaction device; A second pipeline, the second pipeline is connected to the second gas outlet and the first gas inlet respectively, and is used to transport the remaining first oxidizing gas from the catalytic reaction device back to the positive electrode liquid storage tank after the catalyst is oxidized.

2. The liquid flow battery circulation recovery system according to claim 1, characterized in that: The recovery system also includes: A first one-way guide valve is provided on the first pipeline.

3. A liquid flow battery cycle recovery system according to claim 1, characterized in that: Also includes: A positive electrode recovery device, the positive electrode recovery device is connected to the positive electrode liquid storage tank, the positive electrode recovery device can receive the positive electrode electrolyte and promote the positive electrode electrolyte reaction to produce a second oxidizing gas; The positive electrode recovery device is also connected to the catalytic reaction device, and the catalytic reaction device is capable of receiving the second oxidizing gas, and the second oxidizing gas is used to oxidize the catalyst and fix it.

4. A liquid flow battery cycle recovery system according to claim 3, characterized in that: The positive electrode liquid storage tank includes a first liquid outlet and a first liquid inlet, the positive electrode recovery device includes a second liquid inlet and a second liquid outlet, and the recovery system further includes: a third pipeline, the third pipeline being connected to the first liquid outlet and the second liquid inlet, respectively, and being used for transporting the positive electrode electrolyte from the positive electrode storage tank to the positive electrode recovery device; A fourth pipeline, the fourth pipeline is connected to the second liquid outlet and the first liquid inlet respectively, and is used to transport the reacted positive electrode electrolyte back to the positive electrode storage tank.

5. A liquid flow battery cycle recovery system according to claim 4, characterized in that: The positive electrode recovery device further includes a third gas outlet and a third gas inlet; the recovery system further includes: a fifth pipeline, the fifth pipeline being connected to the third gas outlet and the second gas inlet, respectively, and being used for transporting the second oxidizing gas from the positive electrode recovery device to the catalytic reaction device; A sixth pipeline, the sixth pipeline is connected to the second gas outlet and the third gas inlet, respectively, and is used to transport the remaining second oxidizing gas from the catalytic reaction device back to the positive electrode recovery device after the catalyst is oxidized.

6. A liquid flow battery cycle recovery system according to claim 5, characterized in that: The recovery system also includes: A second one-way conducting valve is provided on the fifth pipeline.

7. A liquid flow battery circulation recovery system according to claim 3, characterized in that: The negative electrode liquid storage tank includes a fourth gas outlet and a fourth gas inlet, and the recovery system further includes: a seventh pipeline, the seventh pipeline being connected to the fourth gas outlet and the second gas inlet, respectively, and being used for transporting the first reducing gas from the negative electrode liquid storage tank to the catalytic reaction device; An eighth pipeline, the eighth pipeline is connected to the second gas outlet and the fourth gas inlet, respectively, and is used to transport the gas generated after being oxidized by the catalyst in the catalytic reaction device back to the negative electrode liquid storage tank.

8. A liquid flow battery cycle recovery system according to claim 7, characterized in that: The recovery system also includes: A third one-way conducting valve is provided on the seventh pipeline.

9. A liquid flow battery cycle recovery system according to claim 7, characterized in that: Also includes: a reducing gas source, the reducing gas source being connected to the catalytic reaction device and being used to pass a second reducing gas into the catalytic reaction device; The catalytic reaction device receives the second reducing gas, and the second reducing gas is used to reduce the catalyst that has been oxidized; An exhaust gas treatment device is connected to the negative electrode liquid storage tank and is used to treat the gas discharged from the negative electrode liquid storage tank.

10. A liquid flow battery circulation recovery system according to claim 1, characterized in that: The catalyst is selected from at least one of a copper-based catalyst, a nickel-based catalyst, and a bismuth-based catalyst; or The reducing ions are selected from at least one of chloride ions and bromide ions; or The active ions are selected from at least one of vanadium ions, manganese ions, bromide ions, iron ions, and lead ions; or The supporting electrolyte is selected from at least one of sulfuric acid, hydrochloric acid and phosphoric acid; The first oxidizing gas is selected from at least one of chlorine and bromine; The first reducing gas is hydrogen.

11. A liquid flow battery circulation recovery system according to claim 9, characterized in that: The second oxidizing gas is selected from at least one of chlorine and bromine; or The second reducing gas is selected from at least one of hydrogen, carbon monoxide, methane and propane.

12. A liquid flow battery circulation recovery system according to claim 3, characterized in that: The SOC of the positive electrode electrolyte before the reaction is 60% to 100%; The SOC of the positive electrode electrolyte after the reaction is 50% to 100%.

13. A method for recovering a flow battery cycle, characterized in that: The following steps are involved: The positive electrode storage tank is filled with a positive electrode electrolyte, wherein the positive electrode electrolyte contains reducing ions and active ions, and the reducing ions react with the active ions to reduce the valence of the active ions and generate a first oxidizing gas; Passing the first oxidizing gas into a catalytic reaction device, wherein the catalytic reaction device contains a catalyst, and the first oxidizing gas undergoes a redox reaction with the catalyst and is fixed; The negative electrode storage tank is filled with a negative electrode electrolyte, wherein the negative electrode electrolyte contains a supporting electrolyte, and the supporting electrolyte undergoes a side reaction to generate a first reducing gas; The first reducing gas is introduced into the catalytic reaction device, and a redox reaction occurs between the first reducing gas and the oxidized catalyst. The catalyst is reduced and releases acidic gas. The generated acidic gas can return to the negative electrode storage tank and be absorbed by the negative electrode electrolyte.

14. A method for recovering a flow battery cycle according to claim 13, characterized in that: The molar ratio of the reducing ions to the active ions is (1-10): (0.1-5); Wherein, the concentration of the reducing ions in the positive electrode electrolyte is 0.5-10 mol / L; The concentration of the active ions in the positive electrode electrolyte is 0.1-5 mol / L; The concentration of the supporting electrolyte in the negative electrode electrolyte is 0.5-10 mol / L.

15. A method for recovering a flow battery cycle according to claim 13, characterized in that: The temperature at which the reducing ions react with the active ions is 20-100° C.; or The temperature at which the first oxidizing gas reacts with the catalyst is 20-400° C.; or The reaction temperature of the first reducing gas and the oxidized catalyst is 100-550°C.

16. A method for recovering a flow battery cycle according to claim 13, characterized in that: Before the step of reacting the reducing ions with the active ions, the method further comprises: Passing the positive electrode electrolyte into the positive electrode recovery device, adjusting the temperature to make the positive electrode electrolyte react to generate a second oxidizing gas and reduce the valence of the active ions; A second oxidizing gas is introduced into the catalytic reaction device, and the second oxidizing gas reacts with the catalyst to oxidize the catalyst.

17. A method for recovering a flow battery cycle according to claim 13, characterized in that: In the positive electrode recovery device, the temperature is adjusted in the range of 20~100℃.

18. A method for recovering a flow battery cycle according to claim 13, characterized in that: Before the step of reacting the first oxidizing gas with the catalyst and / or after the step of reacting the first reducing gas with the oxidized catalyst, Passing a second reducing gas provided by a reducing gas source into the catalytic reaction device, and reacting the first reducing gas with at least a portion of the oxidized catalyst to completely reduce the catalyst; The gas after the reaction is introduced into the negative electrode storage tank and absorbed by the negative electrode electrolyte; then it is processed and discharged through the exhaust gas treatment device.

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