A method and device for recovering the capacity of electrolyte of a vanadium redox flow battery and application thereof

Abstract

The application discloses a kind of all-vanadium redox battery electrolyte capacity recovery method, device and application, belong to the technical field of flow battery electrolyte.The all-vanadium redox battery electrolyte capacity recovery method provided by the application comprises: introducing the positive electrolyte and negative electrolyte of the all-vanadium redox battery to be recovered into an electrolysis stack for electrolysis, so that the positive electrolyte and negative electrolyte are electrolyzed;The positive electrolyte after electrolysis is introduced into the positive electrode chamber in the reduction reaction tank, and the reducing solution is introduced into the solution chamber in the reduction reaction tank, and the potential difference between the positive electrolyte and the reducing solution is used to carry out redox reaction;The positive electrolyte in the positive electrode chamber after electrolysis is introduced into the positive electrolyte storage tank of the all-vanadium redox battery, and the negative electrolyte after electrolysis is introduced into the negative electrolyte storage tank of the all-vanadium redox battery, thereby completing the capacity recovery of the all-vanadium redox battery, and has wide application prospect in the field of all-vanadium redox battery.

Description

Technical Field

[0001] This application belongs to the field of flow battery electrolyte technology, and particularly relates to a method, apparatus and application for capacity recovery of vanadium redox flow battery electrolyte. Background Technology

[0002] Vanadium redox flow batteries (VRBs) are a novel energy storage system characterized by fast charge / discharge response, large and adjustable charging capacity, and high battery efficiency, demonstrating significant advantages in the field of stationary renewable energy storage. However, after long-term charge / discharge cycles, the electrolyte capacity decay problem gradually becomes prominent, becoming a key bottleneck restricting its commercial application. To address this issue, researchers have proposed several electrolyte activity recovery technologies, all with the core objective of reversing VRB capacity decay. 2+ / V 5+ The increasing trend of ion valence entropy helps to reconstruct the redox potential balance of the electrolyte.

[0003] For example, prior art application CN 115051005 A discloses a flow battery capacity recovery system and method, which restores vanadium ion balance and improves electrolyte activity through electrolyte mixing, thereby achieving battery capacity recovery. Prior art application CN 111509278 A discloses an online method for restoring the capacity and efficiency of a vanadium redox flow battery, which regenerates the electrolyte by adding a reducing agent (oxalic acid, tartaric acid, hydrazine, etc.) to the electrolyte after long-term cycling. As another example, CN 117727988 A discloses a method and apparatus for capacity recovery of vanadium redox flow battery electrolyte, which restores electrolyte capacity by mixing the vanadium redox flow battery electrolyte with a reducing gas and under the action of a hydrogen reduction catalyst.

[0004] Although the above-mentioned recovery methods can restore electrolyte capacity to a certain extent, the following problems still exist: First, physical mixing operations are complex and can only repair the concentration and volume imbalance of the electrolyte, with limited effect on alleviating the vanadium ion valence state imbalance generated during operation. Furthermore, vanadium ion concentration monitoring mostly employs spectrophotometers and potentiometric titration, which have certain limitations and large measurement errors. Second, chemical reduction methods are prone to introducing contamination due to reagent residues, inducing chain side reactions, such as the residual carboxylate ions (COOH) after oxalic acid reduction. - ) and V in the electrolyte 4+ This combination forms a blue-green precipitate [VO(C2O4)2]. 2- First, it blocks the flow channel and causes irreversible loss of vanadium; second, catalytic reduction usually requires the use of precious metal catalysts and dangerous gases, which is not only costly but also poses great safety hazards, making it difficult to implement in engineering applications. Summary of the Invention

[0005] This application discloses a method, apparatus, and application for restoring the capacity of electrolyte in a vanadium redox flow battery, aiming to solve the technical problems of existing methods for restoring the capacity of electrolyte in vanadium redox flow batteries, such as vanadium ion valence state imbalance, reagent contamination, side reactions, and high cost.

[0006] To achieve the above objectives, the technical solution of this application is:

[0007] The first aspect of this application provides a method for recovering the capacity of an electrolyte in a vanadium redox flow battery, comprising:

[0008] (1) The positive and negative electrolytes of the vanadium redox flow battery to be recovered are introduced into the electrolytic stack for electrolysis, so that the positive electrolyte is electrolyzed into pentavalent vanadium and the negative electrolyte is electrolyzed into divalent vanadium.

[0009] (2) The positive electrode electrolyte after electrolysis in step (1) is introduced into the positive electrode chamber of the reduction reaction tank, and the reducing solution is introduced into the solution chamber of the reduction reaction tank. The spontaneous oxidation-reduction reaction is carried out by utilizing the potential difference between the positive electrode electrolyte and the reducing solution.

[0010] (3) The positive electrolyte in the positive electrode chamber after electrolysis in step (2) is introduced into the positive electrolyte storage tank of the vanadium redox flow battery, and the negative electrolyte after electrolysis in step (1) is introduced into the negative electrolyte storage tank of the vanadium redox flow battery, thereby restoring the electrolyte capacity.

[0011] Preferably, in conjunction with the first aspect, the method further includes:

[0012] A potential monitoring device is used to monitor the potentials of the positive electrode electrolyte, negative electrode electrolyte, and reference electrolyte of the vanadium redox flow battery before and after recovery. Based on the comparison results of the potential difference between the positive electrode electrolyte to be recovered and the negative electrode electrolyte, and the potential difference between the positive electrode electrolyte and the reference electrolyte before and after recovery and the potential difference between the negative electrode electrolyte, the start and stop signals for electrolyte capacity recovery are output.

[0013] The reference electrolyte is a full vanadium redox flow battery electrolyte containing at least one of divalent, trivalent, tetravalent, and pentavalent vanadium ions.

[0014] Preferably, in conjunction with the first aspect, the start / stop signal for restoring the output electrolyte capacity includes:

[0015] The potential difference between V1 and V2 is obtained through a potential monitoring device;

[0016] When the potential monitoring device detects that the potential difference between V1 and V2 is greater than 0.15 V, it outputs a start signal for the recovery method to execute step (1) and outputs an alarm message.

[0017] Wherein, V1 is the potential difference between the positive electrolyte to be restored and the negative electrolyte; V2 is the potential difference between the potential formed by the positive electrolyte to be restored and the reference electrolyte and the negative electrolyte.

[0018] Preferably, in conjunction with the first aspect, the start / stop signal for restoring the output electrolyte capacity includes:

[0019] The potential difference between V1 and V3 is obtained through a potential monitoring device;

[0020] When the potential monitoring device detects that the potential difference between V1 and V3 is less than 0.05 V, it outputs a stop signal for step (3) of the recovery method.

[0021] Wherein, V1 is the potential difference between the positive electrolyte and the negative electrolyte to be restored; V3 is the potential difference between the positive electrolyte and the reference electrolyte after restoration and the negative electrolyte.

[0022] Preferably, in conjunction with the first aspect, the redox reaction utilizing the potential difference between the positive electrode electrolyte and the reducing solution includes:

[0023] The potential of the positive electrolyte in the positive electrode chamber of the reduction reaction tank is higher than the potential of the reducing solution in the solution chamber, and the potential difference is >0.3 V.

[0024] Preferably, in conjunction with the first aspect, the reducing agent in the reducing solution is one or more of oxalic acid, citric acid, ascorbic acid, ethylene glycol, glycerol, tartaric acid, hydrazine, and ferrous ammonium sulfate;

[0025] The solvent in the reducing solution that dissolves the reducing agent is sulfuric acid, hydrochloric acid, or a combination thereof;

[0026] The concentration of the reducing solution is 0.001 M-3 M.

[0027] Preferably, in conjunction with the first aspect, the reduction reaction tank is provided with an ion exchange membrane, which divides the space within the reduction reaction tank into the positive electrode chamber and the solution chamber;

[0028] The ion exchange membrane is one of the following: cation exchange membrane, anion exchange membrane, porous membrane, or composite membrane;

[0029] The ion exchange membrane has a thickness of 50-200 μm and a vanadium ion permeability of <10. -7 cm² / min, proton conductivity greater than 0.02 S / cm.

[0030] The second aspect of this application provides a vanadium redox flow battery electrolyte capacity recovery device, the device being used to implement the vanadium redox flow battery electrolyte capacity recovery method described in the first aspect, comprising:

[0031] A reduction reaction tank is provided with an ion exchange membrane, which divides the reduction reaction tank into a positive electrode chamber and a solution chamber that are ion-conducting but not connected to the solution.

[0032] An electrolytic reactor is used to electrolyze the electrolyte of the vanadium redox flow battery, so that the positive electrode electrolyte in the vanadium redox flow battery is completely electrolyzed into pentavalent vanadium and the negative electrode electrolyte is electrolyzed into divalent vanadium.

[0033] A positive electrode electrolyte circulation path is fluidly connected to the positive electrode of the vanadium redox flow battery, the positive electrode chamber of the reduction reaction tank, the positive electrode electrolyte storage tank, the electrolytic stack, and the positive electrode pump. Driven by the positive electrode pump, the positive electrode electrolyte circulation path circulates the positive electrode electrolyte between the positive electrode chamber, the positive electrode of the vanadium redox flow battery, the positive electrode electrolyte storage tank, and the electrolytic stack.

[0034] The negative electrode electrolyte circulation path is fluidly connected to the negative electrode of the vanadium redox flow battery, the negative electrode electrolyte storage tank, the electrolytic stack, and the negative electrode pump. Driven by the negative electrode pump, the negative electrode electrolyte circulation path allows the negative electrode electrolyte to circulate between the electrolytic stack, the negative electrode of the vanadium redox flow battery, and the negative electrode electrolyte storage tank.

[0035] The reducing agent solution circulation path is fluidly connected to the reducing solution storage tank and the solution chamber of the reduction reaction tank. Driven by the reducing agent pump, the reducing agent solution circulates between the solution chamber and the reducing solution storage tank.

[0036] In conjunction with the second aspect, preferably, the vanadium redox flow battery electrolyte capacity recovery device further includes a control cabinet and a feeding device;

[0037] The control cabinet controls each component through control circuits;

[0038] The feeding device is used to store and dispense reducing reagents.

[0039] The third aspect of this application provides the application of the vanadium redox flow battery electrolyte capacity recovery method described in the first aspect or the vanadium redox flow battery electrolyte capacity recovery device described in the second aspect in the field of vanadium redox flow batteries.

[0040] Compared with the prior art, the advantages or beneficial effects of the embodiments of this application include at least the following:

[0041] The capacity recovery method provided in this application achieves capacity recovery of the vanadium redox flow battery electrolyte by electrolyzing the positive and negative electrode electrolytes. On one hand, no impurity ions are introduced into the positive electrode electrolyte of the vanadium redox flow battery during the entire capacity recovery process, thus avoiding negative impacts on subsequent charge and discharge functions. This fundamentally solves the problem of residual reducing agents, prevents irreversible degradation, and greatly improves system lifespan. On the other hand, the spontaneous redox reaction via potential difference completely avoids dependence on precious metal catalysts and the risks of using hazardous gases, achieving a safe recovery and regeneration process under mild conditions of ambient temperature and pressure. Furthermore, the capacity recovery method for vanadium redox flow battery electrolytes provided in this application can effectively recover large-scale electrolytes independently of energy storage power stations without conflicting with the power grid system. The entire process is fully automated, and the only byproducts are carbon dioxide and water, causing no environmental pollution and making it suitable for industrial production and control. Attached Figure Description

[0042] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments recorded in this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0043] Figure 1 This is a schematic flowchart illustrating the method for restoring the electrolyte capacity of a vanadium redox flow battery according to an embodiment of this application.

[0044] Figure 2 This is a schematic diagram of the arrangement and connection of the apparatus for implementing the method for restoring the electrolyte capacity of a vanadium redox flow battery according to an embodiment of this application;

[0045] In the figure, the labels for each item are as follows: 1-Vanadium redox flow battery system, 2-Vanadium redox flow battery electrolyte recovery system, 3-Positive electrode electrolyte storage tank, 4-Negative electrode electrolyte storage tank, 5-Positive electrode pump, 6-Negative electrode pump, 7-Anode pump, 8-Potential monitoring device, 9-Electrolytic stack, 10-Reduction reaction tank, 11-Jet mixer, 12-Solenoid valve, 13-Feeder, 14-Storage tank, 15-Exhaust port, 16-pH meter, 17-Three-way valve;

[0046] Figure 3 This is a schematic diagram of the potential monitoring device used in the embodiments of this application;

[0047] Figure 4 This is a graph showing the capacity change of the battery before and after adopting the full vanadium redox flow battery electrolyte capacity recovery method in the embodiments of this application. Detailed Implementation

[0048] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0049] In the following description of this embodiment, the term "and / or" is used to describe the association relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, B existing alone, and A and B existing simultaneously. A and B can be singular or plural. The character " / " generally indicates that the preceding and following related objects have an "or" relationship.

[0050] In the following description of this embodiment, the term "at least one" means one or more, and "more than one" means two or more. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of single or multiple items. For example, "at least one of a, b, or c", or "at least one of a, b, and c", can both mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be single or multiple.

[0051] Those skilled in the art should understand that, in the following description of the embodiments of this application, the sequence of numbers does not imply the order of execution. Some or all steps may be executed in parallel or sequentially. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.

[0052] The terminology used in the embodiments of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of this application. The singular forms "a" and "the" as used in the embodiments of this application and the appended claims are also intended to include the plural forms, unless the context clearly indicates otherwise.

[0053] It should be noted that all raw materials and / or reagents in the embodiments of this application were purchased on the market or prepared according to conventional methods known to those skilled in the art.

[0054] In a first aspect, this application provides a method for recovering the capacity of an electrolyte in a vanadium redox flow battery, comprising:

[0055] (1) The positive and negative electrolytes of the vanadium redox flow battery to be recovered are introduced into the electrolytic stack for electrolysis, so that the positive electrolyte is electrolyzed into pentavalent vanadium and the negative electrolyte is electrolyzed into divalent vanadium.

[0056] (2) The positive electrode electrolyte after electrolysis in step (1) is introduced into the positive electrode chamber of the reduction reaction tank, and the reducing solution is introduced into the solution chamber of the reduction reaction tank. The spontaneous oxidation-reduction reaction is carried out by utilizing the potential difference between the positive electrode electrolyte and the reducing solution.

[0057] (3) The positive electrolyte in the positive electrode chamber after electrolysis in step (2) is introduced into the positive electrolyte storage tank of the vanadium redox flow battery, and the negative electrolyte after electrolysis in step (1) is introduced into the negative electrolyte storage tank of the vanadium redox flow battery, thereby restoring the electrolyte capacity.

[0058] It should be noted that: 1. During the capacity recovery process throughout the entire life cycle, no impurity ions are introduced into the vanadium redox flow battery electrolyte, which will not negatively affect the subsequent charge and discharge functions. This fundamentally solves the problem of residual reducing agent, avoids irreversible degradation, and greatly improves the system life. 2. By using a spontaneous redox reaction through potential difference, the consumption of precious metal catalysts and the risks of using hazardous gases, such as hydrogenation catalytic reactions, are completely avoided. This achieves a safe recovery and regeneration process under mild conditions of normal temperature and pressure. At the same time, the vanadium redox flow battery electrolyte capacity recovery device and method provided in this application can easily and continuously achieve effective electrolyte recovery without calling the battery stack of the energy storage power station, balancing the state of charge (SOC) of the battery packs, and will not cause power consumption conflicts with the power grid system. The entire process only requires maintenance personnel to add sufficient reducing agent to the raw material hopper. Sampling analysis, electrolysis, and reduction are all fully automated. Moreover, the only byproducts of the reaction are carbon dioxide and water, which will not cause environmental pollution. The operation is simple and easy to learn, making it particularly suitable for the operation and maintenance of large-scale vanadium redox flow energy storage power stations. The vanadium redox flow battery electrolyte capacity recovery device used in this application can flexibly control the flow rate of the positive and negative electrode electrolytes, and suppress the migration of vanadium ions and the occurrence of hydrogen evolution side reactions.

[0059] In this embodiment, the reducing agent in the reducing solution is preferably one or more of oxalic acid, citric acid, ascorbic acid, ethylene glycol, glycerol, tartaric acid, hydrazine, and ferrous ammonium sulfate; the solvent for dissolving the reducing agent in the reducing solution is sulfuric acid, hydrochloric acid, or a combination thereof. The concentration of the reducing solution is preferably 0.001-3 M, more preferably 0.1-0.5 M. By controlling the concentration of the reducing solution, it is possible to ensure that vanadium (V) in the positive electrode electrolyte is fully reduced, while reducing the problem of side reactions or reagent waste caused by excessive concentration, thereby ensuring the recovery of the battery's normal charge and discharge performance.

[0060] In this embodiment, the reduction reaction tank is equipped with an ion exchange membrane, which divides the space within the reduction reaction tank into the positive electrode chamber and the solution chamber. The ion exchange membrane is preferably one of a cation exchange membrane, anion exchange membrane, porous membrane, or composite membrane. The cation exchange membrane is preferably one of a perfluorosulfonic acid ion exchange membrane, a xanthocyanided polyether ether ketone-based cation exchange membrane, or a composite membrane. The anion exchange membrane is preferably one of a polyarylene ether ketone-based anion exchange membrane, a polybenzimidazole anion exchange membrane, a fluorinated anion exchange membrane, or a non-fluorinated anion exchange membrane. The zwitterionic membrane is preferably one of a xanthocyanided polyether ether ketone-based composite membrane or a polybenzimidazole-based zwitterionic membrane. The thickness of the ion exchange membrane is preferably 50-200 μm, and the vanadium ion permeability is preferably <10. -7 The density of the material is preferably greater than 0.02 S / cm, the thickness is preferably 50-60 μm, and the vanadium ion permeability is preferably less than 10 μm. -8 The ion exchange membrane has a flow rate of cm² / min and a proton conductivity preferably greater than 0.1 S / cm. It is used to block the migration of products undergoing the redox reaction while allowing specific ions to permeate in a directional manner, thereby ensuring the orderly conduct of the reaction.

[0061] In this embodiment, the capacity recovery reaction temperature is preferably 25-90 ℃, more preferably 30-50 ℃, which means that the recovery method of this application can realize the recovery of electrolyte capacity at room temperature.

[0062] In this embodiment, an ion exchange membrane is provided in the reduction reaction tank. The ion exchange membrane is used to block the migration of the products undergoing the redox reaction, dividing the reduction reaction tank into a positive electrode chamber and a solution chamber that are ion-conducting but not solution-conducting. Taking oxalic acid as an example, the reaction occurring in the positive electrode chamber of the reduction reaction tank is specifically: VO2 + +2H + +e - →VO 2+ +H₂O; The specific reaction occurring in the solution chamber is: H₂C₂O₄⁻ 2e⁻ - →2H + +2CO2↑.

[0063] Secondly, this application provides a vanadium redox flow battery electrolyte capacity recovery device, which is used to implement the vanadium redox flow battery electrolyte capacity recovery method described in the first aspect, specifically as follows: Figure 2As shown, the system includes a vanadium redox flow battery system 1 and a vanadium redox flow battery electrolyte recovery system 2. The vanadium redox flow battery system 1 includes a positive electrode electrolyte storage tank 3 and a negative electrode electrolyte storage tank 4; the vanadium redox flow battery electrolyte recovery system 2 includes a positive electrode pump 5, a negative electrode pump 6, an anode pump 7, a potential monitoring device 8, an electrolytic stack 9, a reduction reaction tank 10, a jet mixer 11, a solenoid valve 12, a feeder 13, a storage tank 14, an exhaust port 15, a pH meter 16, a three-way valve 17, and several connecting pipes. The positive electrode electrolyte storage tank 3 is connected to the inlet of the positive electrode pump 5 via a connecting pipe, and the outlet of the positive electrode pump 5 is connected to the positive electrode side inlet of the electrolytic reactor 9 and the positive electrode side inlet of the potential monitoring device 8 via a connecting pipe; the negative electrode electrolyte storage tank 4 is connected to the inlet of the negative electrode pump 6 via a connecting pipe, and the outlet of the negative electrode pump 6 is connected to the negative electrode side inlet of the electrolytic reactor 9 and the potential monitoring device 8 via connecting pipes; the negative electrode side outlet of the potential monitoring device 8 is connected to the negative electrode electrolyte storage tank 4 via a connecting pipe, and the positive electrode side outlet of the potential monitoring device 8 is connected to the inlet of the positive electrode electrolyte storage tank 3 via a connecting pipe; The positive electrode outlet of the decomposition unit 9 is connected to the inlet of the reduction reaction tank 10 via a connecting pipe. The positive electrode outlet of the reduction reaction tank 10 is connected to the positive electrode inlet of the potential monitoring device 8 and the positive electrode electrolyte storage tank 3 via connecting pipes. The inlet of the jet mixer 11 is connected to the feeder 13 via a connecting pipe. The outlet of the jet mixer 11 is connected to the storage tank 14 via a connecting pipe. The solenoid valve 12 is installed on the connecting pipe between the feeder 13 and the jet mixer 11. The pH meter 16 is installed on the connecting pipe between the storage tank 14 and the anode pump 7. The exhaust port 15 is installed on the storage tank 14.

[0064] It should be noted that in the vanadium redox flow battery electrolyte capacity recovery method adopted in this application, during long-term operation of the vanadium redox flow battery, when the potential displayed by the potential monitoring device satisfies |V1-V2|>0.15 V, the electrolytic reactor is automatically started, and the electrolytic reactor cutoff voltage is set to 1.6 V. The positive and negative electrode electrolytes of the vanadium redox flow battery are electrolyzed into vanadium (V) and vanadium (II) forms. After electrolysis, the negative electrode electrolyte returns to the negative electrode electrolyte storage tank through a connecting pipe, and the positive electrode electrolyte flows through the positive electrode chamber of the reduction reaction tank and returns to the positive electrode electrolyte storage tank after passing through the potential monitoring device. When the electrolytic reactor voltage reaches 1.6 V, the anode pump 7 and solenoid valve 12 are automatically opened. After the reducing solution is mixed evenly, the three-way valve 17 is opened to introduce the reducing solution into the solution chamber of the reduction reaction tank, and the electrolyte capacity recovery begins. When the potential displayed by the potential monitoring device meets |V1-V3| < 0.05 V, the capacity recovery is complete. Then, the anode pump 7 and the three-way valve 17 are closed, thus completing the electrolyte capacity recovery.

[0065] It should be noted that the reference electrolyte used in this application is a full vanadium redox flow battery electrolyte containing at least one of divalent, trivalent, tetravalent, and pentavalent vanadium ions, or a full vanadium redox flow battery electrolyte containing a mixture of divalent and trivalent, tetravalent and pentavalent vanadium ions in any target state of charge.

[0066] It should be noted that this application uses an electrolytic reactor to transfer charge in the electrolyte of the vanadium redox flow battery. By adjusting the flow rate and electrolysis current of the positive and negative electrode pumps, the positive electrode electrolyte in the vanadium redox flow battery is electrolyzed into a high SOC state that is close to the complete pentavalent vanadium state after flowing through the electrolytic reactor. In the negative electrode electrolyte, some vanadium ions gain electrons and reduce their valence state before returning to the negative electrode electrolyte storage tank.

[0067] It should be noted that the feeding device used in this application is for storing and dispensing reducing reagents. Preferably, the feeding device uses a reducing agent pump as a power source and a jet mixer to assist in the uniform mixing of the solid and liquid phases.

[0068] Thirdly, this application also provides the application of the vanadium redox flow battery electrolyte capacity recovery method described in the first aspect or the vanadium redox flow battery electrolyte capacity recovery device described in the second aspect in the field of vanadium redox flow batteries. Based on the above methods, large-scale electrolyte recovery can be effectively achieved independently of energy storage power stations without causing power grid conflicts; the entire process is fully automated, and the only byproducts are carbon dioxide and water, which will not cause environmental pollution, thus showing broad application prospects in the field of vanadium redox flow batteries.

[0069] The technical solution of this application will be further described below with reference to specific embodiments.

[0070] Example 1

[0071] This embodiment provides a method for restoring the electrolyte capacity of a vanadium redox flow battery, the flowchart of which is shown below. Figure 1 As shown, it specifically includes:

[0072] S101: The electrolyte for the all-vanadium redox flow battery uses a sulfuric acid system, with a vanadium ion concentration of 1.65 M and a sulfuric acid concentration of 3 mol / L. 100 mL of electrolyte is used on each of the positive and negative electrode sides. The electrolyte concentration is [not specified] at 160 mA / cm². 2 It operates at a current density of 0.5 mol / L H2C2O4 + 3 mol / L H2SO4. The reference electrolyte in the potential monitoring device is a tetravalent vanadium solution with the same concentration as the positive electrode electrolyte.

[0073] S102: During long-term operation of the vanadium redox flow battery, when the potential displayed by the potential monitoring device meets |V1-V2|>0.15 V, the electrolytic reactor is automatically started, and the electrolytic reactor cutoff voltage is set to 1.6 V. The positive and negative electrode electrolytes of the vanadium redox flow battery are electrolyzed into vanadium (V) and vanadium (II) forms. After electrolysis, the negative electrode electrolyte returns to the negative electrode electrolyte storage tank through a connecting pipe, and the positive electrode electrolyte flows through the positive electrode chamber of the reduction reaction tank and returns to the positive electrode electrolyte storage tank after passing through the potential monitoring device. When the electrolytic reactor voltage reaches 1.6 V, the anode pump 7 and solenoid valve 12 are automatically opened. After the reducing solution is mixed evenly, the three-way valve 17 is opened to introduce the reducing solution into the solution chamber of the reduction reaction tank, and the electrolyte capacity recovery begins. When the potential displayed by the potential monitoring device meets |V1-V3|<0.05 V, the capacity recovery is complete, and the anode pump 7 and three-way valve 17 are closed.

[0074] This application uses electrochemical titration analysis to compare the vanadium ion concentration before and after recovery. The electrochemical titration analysis procedure is performed in accordance with the test method section of NB / T 42006-2013 for electrolytes used in all-vanadium redox flow batteries.

[0075] Table 1. Parameter values ​​of electrolyte before and after recovery

[0076]

[0077] As shown in Table 1, after restoration using the method described in this application, the average valence state of vanadium ions in the vanadium redox flow battery electrolyte is restored to an average valence state of 3.51.

[0078] according to Figure 2 As can be seen, when the potential monitoring device 8 deviates from the preset threshold, the electrolyte recovery device is activated. First, the positive electrode pump 5 and the negative electrode pump 6 are activated to transport the positive and negative electrode electrolytes to the electrolytic reactor 9 through the connecting pipe. The vanadium redox flow battery electrolyte to be recovered is electrolyzed through the electrolytic reactor, so that the positive electrode electrolyte is completely oxidized to vanadium (V) and the negative electrode electrolyte is completely reduced to vanadium (II). The positive electrode electrolyte enters the positive electrode chamber of the reduction reaction tank 10 through the outlet of the electrolytic reactor 9, and then returns to the positive electrode electrolyte storage tank 3 through the potential monitoring device 8. After the electrolytic reactor 9 completes electrolysis, the anode pump 7 and the solenoid valve 12 are activated. The solvent and reducing agent in the storage tank are mixed in the jet mixer 11, and then enter the solution chamber of the reduction reaction tank 10 through the connecting pipe to restore the electrolyte capacity. When the potential monitoring device 8 reaches the preset threshold, the electrolyte recovery is completed.

[0079] according to Figure 3The diagram shows the structure of the potential monitoring device 8. Its core structure consists of a single-cell vanadium redox flow battery, a dual-cell vanadium redox flow battery, and a central groove for storing the reference electrolyte. The single-cell vanadium redox flow battery on one side of the groove receives the negative electrode electrolyte and the positive electrode electrolyte restored by the reduction reaction tank. The dual-cell vanadium redox flow battery on the other side of the groove receives the negative electrode electrolyte and the positive electrode electrolyte in the positive electrode storage tank. The positive electrode electrolyte to be restored refers to the positive electrode electrolyte in the positive electrode storage tank, and the restored positive electrode electrolyte refers to the positive electrode electrolyte after treatment by the reduction reaction tank. V1 is the potential difference between the positive electrode electrolyte to be restored and the negative electrode electrolyte; V2 is the potential difference between the potential formed by the positive electrode electrolyte to be restored and the reference electrolyte and the negative electrode electrolyte; V3 is the potential difference between the potential formed by the restored positive electrode electrolyte and the reference electrolyte and the negative electrode electrolyte.

[0080] To verify the battery capacity before and after capacity recovery of the electrolyte in the all-vanadium redox flow battery prepared in the embodiments of this application, the results are as follows: Figure 4 As shown.

[0081] according to Figure 4 It can be seen that the all-vanadium redox flow battery achieves a current density of 160 mA / cm². 2 During operation, when the capacity decreased from 3.07 Ah to 2.36 Ah, the potential monitor alarmed, and the electrolyte recovery device was activated. After restoring the electrolyte activity using the method described in this application, the capacity recovered from 2.36 Ah to 2.98 Ah, and the recovered vanadium redox flow battery capacity reached 97% of the initial electrolyte capacity. Potentiometric titration tests verified that after restoring the electrolyte activity using the method described in this application, the average vanadium ion valence state recovered from 3.68 to 3.51. The recovery of electrolyte capacity and reactivity is achieved by correcting the electrolyte valence state.

[0082] Therefore, the capacity of vanadium redox flow batteries shows significant decay after long-term cycling. The vanadium redox flow battery electrolyte capacity recovery method provided in this application firstly electrolyzes the vanadium redox flow battery electrolyte into vanadium (V) and vanadium (II) forms through an external electrolytic reactor, thereby regenerating the negative electrode electrolyte. Secondly, the positive electrode electrolyte after electrolysis is passed through a reduction reaction tank to reduce vanadium (V) to vanadium (IV). Then, a potential monitoring device is used to determine the electrolyte recovery status, ultimately achieving full vanadium redox flow battery capacity recovery. The vanadium redox flow battery electrolyte capacity recovery device provided in this application can effectively restore large-scale positive and negative electrode electrolytes independently of energy storage power stations, without causing power supply conflicts with the power grid system. The entire process is fully automated, and the only byproducts of the reaction are carbon dioxide and water, which will not cause environmental pollution, making it suitable for industrial production and control.

[0083] The various embodiments in this specification are described in a progressive manner. The same or similar parts between the various embodiments can be referred to each other. Each embodiment focuses on describing the differences from other embodiments.

[0084] The above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit this application. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of this application.

Claims

1. A method for restoring the capacity of an electrolyte in a vanadium redox flow battery, characterized in that, include: (1) The positive and negative electrolytes of the vanadium redox flow battery to be recovered are introduced into the electrolytic stack for electrolysis, so that the positive electrolyte is electrolyzed into pentavalent vanadium and the negative electrolyte is electrolyzed into divalent vanadium. (2) The positive electrode electrolyte after electrolysis in step (1) is introduced into the positive electrode chamber of the reduction reaction tank, and the reducing solution is introduced into the solution chamber of the reduction reaction tank. The spontaneous oxidation-reduction reaction is carried out by utilizing the potential difference between the positive electrode electrolyte and the reducing solution. (3) The positive electrolyte in the positive electrode chamber after electrolysis in step (2) is introduced into the positive electrolyte storage tank of the vanadium redox flow battery, and the negative electrolyte after electrolysis in step (1) is introduced into the negative electrolyte storage tank of the vanadium redox flow battery, thereby restoring the electrolyte capacity. A potential monitoring device is used to monitor the potentials of the positive electrode electrolyte, negative electrode electrolyte, and reference electrolyte of the vanadium redox flow battery before and after recovery. Based on the comparison results of the potential difference between the positive electrode electrolyte to be recovered and the negative electrode electrolyte, and the potential difference between the positive electrode electrolyte and the reference electrolyte before and after recovery and the potential difference between the negative electrode electrolyte, the start and stop signals for electrolyte capacity recovery are output. The reference electrolyte is a full vanadium redox flow battery electrolyte containing at least one of divalent, trivalent, tetravalent, and pentavalent vanadium ions.

2. The method for restoring the electrolyte capacity of a vanadium redox flow battery according to claim 1, characterized in that, The start / stop signal for restoring the output electrolyte capacity includes: The potential difference between V1 and V2 is obtained through a potential monitoring device; When the potential monitoring device detects that the potential difference between V1 and V2 is greater than 0.15 V, it outputs a start signal for the recovery method to execute step (1) and outputs an alarm message. Wherein, V1 is the potential difference between the positive electrolyte to be restored and the negative electrolyte; V2 is the potential difference between the potential formed by the positive electrolyte to be restored and the reference electrolyte and the negative electrolyte.

3. The method for restoring the electrolyte capacity of a vanadium redox flow battery according to claim 1, characterized in that, The start / stop signal for restoring the output electrolyte capacity includes: The potential difference between V1 and V3 is obtained through a potential monitoring device; When the potential monitoring device detects that the potential difference between V1 and V3 is less than 0.05 V, it outputs a stop signal for step (3) of the recovery method. Wherein, V1 is the potential difference between the positive electrolyte and the negative electrolyte to be restored; V3 is the potential difference between the positive electrolyte and the reference electrolyte after restoration and the negative electrolyte.

4. The method for restoring the electrolyte capacity of a vanadium redox flow battery according to claim 1, characterized in that, The potential of the positive electrolyte in the positive electrode chamber of the reduction reaction tank is higher than the potential of the reducing solution in the solution chamber, and the potential difference is >0.3 V.

5. The method for restoring the electrolyte capacity of a vanadium redox flow battery according to claim 1, characterized in that, The reducing agent in the reducing solution is one or more of oxalic acid, citric acid, ascorbic acid, ethylene glycol, glycerol, tartaric acid, hydrazine, and ferrous ammonium sulfate. The solvent in the reducing solution that dissolves the reducing agent is sulfuric acid, hydrochloric acid, or a combination thereof; The concentration of the reducing solution is 0.001 M-3 M.

6. The method for restoring the electrolyte capacity of a vanadium redox flow battery according to claim 1, characterized in that, The reduction reaction tank is equipped with an ion exchange membrane, which divides the space inside the reduction reaction tank into the positive electrode chamber and the solution chamber. The ion exchange membrane is either a cation exchange membrane or an anion exchange membrane; The ion exchange membrane has a thickness of 50-200 μm and a vanadium ion permeability of <10. -7 cm² / min, proton conductivity greater than 0.02 S / cm.

7. A capacity recovery device for an all-vanadium redox flow battery electrolyte, characterized in that, The apparatus is used to implement the capacity recovery method for the electrolyte of a vanadium redox flow battery according to any one of claims 1-6, comprising: A reduction reaction tank is provided with an ion exchange membrane, which divides the reduction reaction tank into a positive electrode chamber and a solution chamber that are ion-conducting but not connected to the solution. An electrolytic reactor is used to electrolyze the electrolyte of the vanadium redox flow battery, so that the positive electrode electrolyte in the vanadium redox flow battery is completely electrolyzed into pentavalent vanadium and the negative electrode electrolyte is electrolyzed into divalent vanadium. A positive electrode electrolyte circulation path is fluidly connected to the positive electrode of the vanadium redox flow battery, the positive electrode chamber of the reduction reaction tank, the positive electrode electrolyte storage tank, the electrolytic stack, and the positive electrode pump. Driven by the positive electrode pump, the positive electrode electrolyte circulation path circulates the positive electrode electrolyte between the positive electrode chamber, the positive electrode of the vanadium redox flow battery, the positive electrode electrolyte storage tank, and the electrolytic stack. The negative electrode electrolyte circulation path is fluidly connected to the negative electrode of the vanadium redox flow battery, the negative electrode electrolyte storage tank, the electrolytic stack, and the negative electrode pump. Driven by the negative electrode pump, the negative electrode electrolyte circulation path allows the negative electrode electrolyte to circulate between the electrolytic stack, the negative electrode of the vanadium redox flow battery, and the negative electrode electrolyte storage tank. The reducing agent solution circulation path is fluidly connected to the reducing solution storage tank and the solution chamber of the reduction reaction tank. Driven by the reducing agent pump, the reducing agent solution circulates between the solution chamber and the reducing solution storage tank.

8. The vanadium redox flow battery electrolyte capacity recovery device according to claim 7, characterized in that, The full vanadium redox flow battery electrolyte capacity recovery device also includes a control cabinet and a feeding device; The control cabinet controls each component through control circuits; The feeding device is used to store and dispense reducing reagents.

9. The application of the vanadium redox flow battery electrolyte capacity recovery method according to any one of claims 1-6 or the vanadium redox flow battery electrolyte capacity recovery device according to any one of claims 7-8 in the field of vanadium redox flow batteries.

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