Electrolyte rebalancing system of aqueous organic flow battery

Abstract

The utility model provides an electrolyte rebalancing system of an aqueous organic flow battery, which comprises the aqueous organic flow battery and an electrolyte rebalancing device, and the electrolyte rebalancing device comprises a negative electrode electrolyte rebalancing device and / or a positive electrode electrolyte rebalancing device. The electrolyte rebalancing system of the aqueous organic flow battery is simple, reasonable and compact in structure, extra electrochemical devices and extra chemical reagents are not introduced, and unbalanced electrolyte is rebalanced by designing a reserved interface and a bypass on an original battery system and introducing air into the electrolyte storage tank, so that the service life of the battery system is prolonged, and the service life of the battery system is prolonged. The problem of capacity imbalance after long-term operation of the water-based organic flow battery is solved, the service life of the water-based organic flow battery is prolonged, and the water-based organic flow battery has good application prospect and large-scale popularization potential in the field of electrolyte rebalance after long-term operation of the water-based organic flow battery.

Description

Technical Field

[0001] This utility model relates to aqueous organic flow battery technology, and more particularly to an electrolyte rebalancing system for aqueous organic flow batteries. Background Technology

[0002] Flow batteries, as a novel energy storage technology, have attracted much attention due to their suitability for large-scale, long-term energy storage. Among them, aqueous organic flow batteries demonstrate broad application prospects due to the high designability of their molecules.

[0003] However, as a type of electrochemical energy storage technology, aqueous organic flow batteries experience a slow capacity decay during long-term charge-discharge cycles. The main reasons include:

[0004] (1) Organic active molecules that undergo electrochemical reactions permeate across the membrane;

[0005] (2) Thermal decomposition of organic active molecules;

[0006] (3) Battery side reactions.

[0007] Among these, the capacity decay caused by the thermal decomposition of organic active molecules is irreversible because the functional groups no longer exist after decomposition or the electrochemical reaction is no longer reversible. Transmembrane permeation and battery side reactions, on the other hand, can lead to an imbalance in the capacity of the positive and negative electrode electrolytes. This imbalance can be restored by adjusting the oxidized or reduced state of the active molecules.

[0008] In inorganic metal flow batteries (such as vanadium redox flow batteries, iron-chromium flow batteries, and iron redox flow batteries), capacity decay is typically caused by hydrogen evolution, transmembrane migration of metal ions, and oxidation of low-valence metals, ultimately leading to the accumulation of high-valence metal ions. When the valence shift is not severe, partial capacity recovery can be achieved by mixing the solutions; however, when the valence shift is severe, it is necessary to add a reducing agent or reduce the high-valence metal ions through electrochemical methods.

[0009] Patent CN115051005B discloses a flow battery capacity recovery system and method. By designing a bypass in the main piping system, when the battery capacity decays to a certain level, the bypass is activated, allowing for thorough mixing of the positive and negative electrolytes, thereby achieving capacity recovery. This method is simple and effective, but it only shows significant effects on capacity decay caused by transmembrane permeation of the positive and negative electrode active materials. For capacity decay caused by side reactions such as hydrogen evolution and oxidation, it is necessary to adjust the ion valence state.

[0010] Patent CN103762377B discloses a vanadium battery and a method for rebalancing its electrolyte. The device includes a low-valent vanadium ion supply device and a high-valent vanadium ion recovery device. Low-valent vanadium ions flow into the positive electrode electrolyte storage tank to neutralize pentavalent vanadium ions. Excess high-valent vanadium ions are collected by the recovery device and then reduced to low-valent vanadium ions by chemical or electrochemical methods for subsequent use.

[0011] There are various methods for chemically reducing high-valence vanadium ions. Patent CN106876814B discloses a method for restoring the capacity of a vanadium redox flow battery, using ferrous ammonium sulfate as a reducing agent. This agent is added to the positive electrode electrolyte during any charge / discharge process to reduce high-valence vanadium ions, thereby adjusting their valence state and achieving capacity recovery. Patent CN110911722B discloses a capacity-restoring agent for vanadium redox flow battery electrolytes, its preparation method, and its applications. The reducing agent is made into organic molecular spheres with a density lower than the electrolyte, floating on the electrolyte surface without affecting normal electrolyte circulation or clogging electrolyte inlet / outlet pipes. Patent CN111509278B discloses a method for online restoration of the capacity and efficiency of a vanadium redox flow battery. The positive and negative electrode electrolytes are first mixed, and then a reducing agent such as oxalic acid, tartaric acid, hydrazine, and hydrogen sulfide is added to the positive electrode electrolyte to reduce high-valence vanadium ions to a low-valence state, achieving capacity recovery.

[0012] Patent CN116387583B discloses a method for restoring the capacity of a vanadium redox flow battery. It uses a combination of electrochemical and chemical methods. First, the battery is charged, then a reducing agent is added to the positive electrode storage tank, and finally the end of the restoration process is determined by titrating the valence state of the electrolyte.

[0013] In addition, patent CN222380602U discloses a mobile capacity recovery vehicle and capacity recovery system for vanadium redox flow batteries. It uses a mobile capacity recovery device that is connected to the storage tank that needs to be restored through a reserved interface. Vanadium pentoxide (for negative electrode storage tanks) or vanadium trioxide (for positive electrode storage tanks) and acid are added to the tank. After the reaction is complete, the valence state of the electrolyte is adjusted to the set value. Finally, the device interface is disassembled and the device is moved to the next location that needs capacity recovery.

[0014] Patent CN118281259B discloses a rebalancing device and method for an iron-chromium flow battery electrolyte. The iron electrolyte is used as the cathode of the rebalancing device, and concentrated hydrochloric acid is used as the anode. Through an electrochemical reaction, chloride ions in the anode electrolyte lose electrons and are converted into chlorine gas, which is absorbed by the alkaline solution tank. Meanwhile, ferric ions in the cathode electrolyte gain electrons and are converted into ferrous ions, thus achieving the purpose of rebalancing.

[0015] Patent CN114824369B discloses a rebalancing method for an all-iron flow battery electrolyte. The positive electrode electrolyte to be balanced is used as the cathode of the rebalancing reactor, and organic small molecule fuel is used as the anode to form a fuel cell. Through an electrochemical reaction, the anode fuel is consumed, and the high-valence iron ions at the cathode are reduced to low-valence iron ions, thereby achieving the purpose of rebalancing.

[0016] The electrolyte rebalancing or capacity recovery methods disclosed in the above patents can be mutually referenced in inorganic metal-based flow batteries, as their capacity decay is usually caused by the accumulation of high-valence metal ions, which can be restored through chemical or electrochemical reduction. However, these methods are not applicable to aqueous organic flow batteries that use organic molecules as electrochemical active materials. The positive and negative electrode electrolytes in aqueous organic flow batteries typically use organic compounds with different structures; after mixing, the positive and negative electrode materials react with each other. Although the battery can still operate, its effective capacity is significantly reduced.

[0017] Furthermore, the degradation mechanisms of aqueous organic flow batteries differ significantly. For capacity imbalance in the positive electrode electrolyte, oxidation or reduction operations can be performed, as can corresponding operations on the negative electrode electrolyte; similarly, for capacity imbalance in the negative electrode electrolyte, corresponding operations can be performed on the positive electrode electrolyte. Oxidation or reduction operations can employ chemical methods (such as adding oxidizing or reducing agents) or electrochemical methods (i.e., introducing electrochemical devices, using the electrolyte to be balanced as the cathode or anode, and selecting suitable materials as the anode or cathode to induce an electrochemical reaction). Among the many feasible methods, it is necessary to select methods that are simple to operate, easy to scale, and do not significantly affect other battery performance characteristics, based on the needs of commercial applications. However, there are relatively few published patents regarding capacity recovery in aqueous organic flow batteries.

[0018] Patent CN118216026A discloses a system and process for rebalancing the state of charge of a flow battery. This method employs an electrochemical approach, where the electrolyte to be balanced serves as one electrode of the rebalancing battery, and the other electrode closes the circuit via an oxygen evolution reaction. This method requires the introduction of an electrochemical reaction device, and for the oxygen evolution reaction to occur successfully, the oxygen electrode of the rebalancing battery needs optimization. Furthermore, a voltage needs to be applied across the battery, consuming additional energy.

[0019] Patent CN118867325A discloses a method for restoring the performance of a flow battery. The method involves first discharging the battery, then connecting an external adjustable power load to reduce the voltage level of each battery cell to below 0.3V, thereby restoring the battery capacity. While this method can restore the performance of flow batteries, it has limitations in large-scale applications. Utility Model Content

[0020] The purpose of this invention is to address the aforementioned problems by proposing an electrolyte rebalancing system for aqueous organic flow batteries. This system does not introduce additional electrochemical devices or chemical reagents. By designing reserved interfaces and bypasses on the existing battery system, air is introduced into the electrolyte storage tank to rebalance the unbalanced electrolyte. This solves the capacity imbalance problem of aqueous organic flow batteries after long-term operation, improves the service life of aqueous organic flow batteries, and has good application prospects and large-scale promotion potential in the field of electrolyte rebalancing of aqueous organic flow batteries after long-term operation.

[0021] It should be noted that, in this utility model, unless otherwise specified, the specific meaning of "comprising" in relation to composition and description includes both open-ended meanings such as "comprising," "including," etc., and closed-ended meanings such as "composed of," "consisting of," etc., and similar meanings.

[0022] To achieve the above objectives, the technical solution adopted by this utility model is: an electrolyte rebalancing system for an aqueous organic flow battery includes an aqueous organic flow battery and an electrolyte rebalancing device.

[0023] The aqueous organic flow battery includes: a flow battery stack, a positive electrode electrolyte storage tank, a negative electrode electrolyte storage tank, a positive electrode circulation pump, a negative electrode circulation pump, a positive electrode inlet pipe, a positive electrode return pipe, a negative electrode inlet pipe, and a negative electrode return pipe; the outlet of the positive electrode electrolyte storage tank is connected to the positive electrode electrolyte inlet of the flow battery stack via the positive electrode inlet pipe, and a positive electrode circulation pump is installed in the positive electrode inlet pipe; the outlet of the positive electrode electrolyte of the flow battery stack is connected to the inlet of the positive electrode electrolyte storage tank via the positive electrode return pipe; the outlet of the negative electrode electrolyte storage tank is connected to the negative electrode electrolyte inlet of the flow battery stack via the negative electrode inlet pipe, a negative electrode circulation pump is installed in the negative electrode inlet pipe, and the outlet of the negative electrode electrolyte of the flow battery stack is connected to the inlet of the negative electrode electrolyte storage tank via the negative electrode return pipe;

[0024] The electrolyte rebalancing device includes: a negative electrode electrolyte rebalancing device and / or a positive electrode electrolyte rebalancing device;

[0025] The negative electrode electrolyte rebalancing device includes: a negative electrode inlet valve, a negative electrode outlet valve, a negative electrode inlet pipeline, and a negative electrode outlet pipeline; the negative electrode electrolyte storage tank is connected to the negative electrode inlet pipeline, the negative electrode inlet pipeline is equipped with a negative electrode inlet valve, the negative electrode inlet pipeline is connected to an oxygen source, and oxygen is introduced into the negative electrode electrolyte storage tank through the negative electrode inlet pipeline to rebalance the electrolyte in the storage tank that has an unbalanced capacity; the negative electrode electrolyte storage tank is connected to the negative electrode outlet pipeline, and the negative electrode outlet pipeline is equipped with a negative electrode outlet valve;

[0026] The positive electrode electrolyte rebalancing device includes: a positive electrode inlet valve, a positive electrode outlet valve, a positive electrode inlet pipeline, and a positive electrode outlet pipeline; the positive electrode electrolyte storage tank is connected to the positive electrode inlet pipeline, the positive electrode inlet pipeline is equipped with a positive electrode inlet valve, and the positive electrode inlet pipeline is connected to an oxygen source; the positive electrode electrolyte storage tank is connected to the positive electrode outlet pipeline, and the positive electrode outlet pipeline is equipped with a positive electrode outlet valve.

[0027] Furthermore, the flow battery stack is a flow-through electrolyte flow structure or a flow-by electrolyte flow structure.

[0028] Furthermore, the positive electrode liquid inlet pipe, the positive electrode liquid return pipe, the negative electrode liquid inlet pipe, and the negative electrode liquid return pipe are plastic pipes.

[0029] Furthermore, the positive electrode inlet pipe, positive electrode return pipe, negative electrode inlet pipe, and negative electrode return pipe are made of oxygen-permeable materials, such as polyvinyl chloride (PVC), polyethylene (PE), and polypropylene (PP). When the battery is charging or discharging, if the negative electrode inlet pipe and negative electrode return pipe are made of oxygen-permeable materials, the negative electrode air inlet valve, negative electrode air outlet valve, negative electrode bypass inlet valve, and negative electrode bypass outlet valve remain closed, allowing balancing operations to occur online in real time within the negative electrode inlet pipe and negative electrode return pipe.

[0030] Furthermore, the oxygen source can be a pure oxygen source or a mixture of oxygen and other inert gases, with the oxygen content in the mixture ranging from 1% to 99%. Other inert gases can be nitrogen, helium, argon, etc.

[0031] Furthermore, the side of the negative electrode electrolyte storage tank near its outlet is connected to the negative electrode air inlet pipe, and the side of the negative electrode electrolyte storage tank near its inlet is connected to the negative electrode air outlet pipe.

[0032] Furthermore, the positive electrode electrolyte storage tank is connected to the positive electrode inlet pipe on the side near its outlet; the positive electrode electrolyte storage tank is connected to the positive electrode outlet pipe on the side near its inlet.

[0033] Furthermore, the electrolyte rebalancing device also includes: a negative electrode bypass pipeline, a negative electrode bypass inlet valve, a negative electrode inlet valve, a negative electrode bypass outlet valve, and a negative electrode outlet valve;

[0034] The negative electrode inlet pipeline and the negative electrode return pipeline are connected by a negative electrode bypass pipeline. A negative electrode bypass inlet valve is installed in a section of the negative electrode bypass pipeline near the negative electrode inlet pipeline, and a negative electrode bypass outlet valve is installed in a section of the negative electrode bypass pipeline near the negative electrode return pipeline. A negative electrode inlet valve is installed in the negative electrode inlet pipeline between the negative electrode bypass pipeline and the negative electrode electrolyte inlet of the flow battery stack, and a negative electrode outlet valve is installed in the negative electrode return pipeline between the negative electrode bypass pipeline and the negative electrode electrolyte outlet of the flow battery stack.

[0035] Furthermore, the positive electrode electrolyte rebalancing device also includes: a positive electrode bypass pipeline, a positive electrode bypass inlet valve, a positive electrode inlet valve, a positive electrode bypass outlet valve, and a positive electrode outlet valve;

[0036] The positive electrode inlet pipeline and the positive electrode return pipeline are connected through a positive electrode bypass pipeline. A positive electrode bypass inlet valve is installed in a section of the positive electrode bypass pipeline near the positive electrode inlet pipeline, and a positive electrode bypass outlet valve is installed in a section of the positive electrode bypass pipeline near the positive electrode return pipeline. A positive electrode inlet valve is installed in the positive electrode inlet pipeline between the positive electrode bypass pipeline and the positive electrode electrolyte inlet of the flow battery stack, and a positive electrode outlet valve is installed in the positive electrode return pipeline between the positive electrode bypass pipeline and the positive electrode electrolyte outlet of the flow battery stack.

[0037] Furthermore, the negative electrode electrolyte storage tank is equipped with a pH detection structure. During rebalancing, the pH of the negative electrode electrolyte needs to be monitored and maintained below 9. The rebalancing operation is considered complete when the pH reaches 8.

[0038] Furthermore, a pH detection structure is provided inside the positive electrode electrolyte storage tank.

[0039] The working principle of the electrolyte rebalancing system of this novel aqueous organic flow battery is as follows:

[0040] This invention is applicable to aqueous organic flow batteries. For example, patent CN108140864B discloses a positive and negative electrode electrolyte pairing scheme, wherein the effective reactant of the positive electrode electrolyte is a derivative based on 2,2,6,6-tetramethylpiperidine oxygen radical, and the effective reactant of the negative electrode electrolyte is a derivative based on 4,4'-bipyridine. The electrochemical reaction equations are attached. Figure 1As shown. Even if the substituents on the piperidine ring or nitrogen atom change, the principle of this invention still applies. Furthermore, even if multiple active molecules are linked by carbon chains to form a polymer electrolyte (as described in DE102014001816A1), the principle of this invention still applies because the main structure of the electrochemical reaction remains unchanged: the electron transfer reaction site of the positive electrode electrolyte is located on the nitroxide radical of the piperidine ring, while the electron transfer reaction site of the negative electrode electrolyte is located on the nitrogen atom and ring of 4,4'-bipyridine. Moreover, this invention is also applicable if other organic compounds have similar chemical and electrochemical properties to 4,4'-bipyridine.

[0041] When the positive electrode material undergoes self-discharge due to intermolecular interactions caused by high operating temperature, or when the negative electrode electrolyte permeates across the membrane to the positive electrode side, triggering self-discharge, it leads to the accumulation of charged states in the negative electrode electrolyte, resulting in capacity imbalance. This invention utilizes virtually cost-free air as an oxidant to oxidize the accumulated charged states in the negative electrode electrolyte back to their initial state, thereby adjusting the capacity imbalance of the positive electrode electrolyte and achieving capacity recovery.

[0042] The electrolyte rebalancing system of this aqueous organic flow battery has the following advantages compared with the prior art:

[0043] 1) This utility model solves the capacity imbalance problem of aqueous organic flow batteries after long-term operation, improves the service life of aqueous organic flow batteries, and has great commercial value.

[0044] 2) This invention does not introduce any additional electrochemical devices. It restores the battery capacity simply by introducing air / oxygen into the electrolyte storage tank. The entire reaction process is rapid, does not introduce any additional chemical reagents, and does not produce any extra impurities.

[0045] 3) In inorganic metal flow batteries, air or oxygen is often one of the causes of capacity imbalance, but it can be used as a rebalancing method in aqueous organic flow batteries. The rebalancing system has a simple, reasonable and compact structure and can realize online dynamic correction and rebalancing, which greatly reduces the cost of its commercial application.

[0046] In summary, the electrolyte rebalancing system of this utility model of aqueous organic flow battery does not introduce additional electrochemical devices or chemical reagents. By designing reserved interfaces and bypasses on the original battery system, air is introduced into the electrolyte storage tank to rebalance the unbalanced electrolyte, thus solving the capacity imbalance problem of aqueous organic flow battery after long-term operation and improving the service life of aqueous organic flow battery. Attached Figure Description

[0047] Appendix Figure 1The electrochemical reaction equations for charging and discharging the positive and negative electrolytes of an aqueous organic flow battery are shown. The structural formula to the left of the vertical dashed line is the positive electrolyte, and the structural formula to the right of the vertical dashed line is the negative electrolyte.

[0048] Appendix Figure 2 A schematic diagram of the basic components of an aqueous organic flow battery;

[0049] Appendix Figure 3 This diagram illustrates the electrolyte flow patterns used in flow battery stacks. The structure on the left represents a flow-through electrolyte flow pattern, while the structure on the right represents a flow-by electrolyte flow pattern.

[0050] Appendix Figure 4 A schematic diagram of the apparatus for rebalancing operations from the negative electrode storage tank;

[0051] Appendix Figure 5 A schematic diagram of a device for rebalancing operations from the positive electrode storage tank;

[0052] Appendix Figure 6 A schematic diagram of the air interface in the rebalancing system;

[0053] Appendix Figure 7 The figure represents the change in battery discharge capacity before and after the rebalancing operation with the number of cycles. Cycles 1 to 100 represent the battery discharge capacity before the rebalancing operation, and cycles 101 to 110 represent the battery discharge capacity after the rebalancing operation.

[0054] The attached figures are labeled as follows:

[0055] 1-Flow battery stack, 2-Positive electrode electrolyte storage tank, 3-Negative electrode electrolyte storage tank, 4-Positive electrode circulation pump, 5-Negative electrode circulation pump, 6-Positive electrode inlet pipe, 7-Negative electrode inlet pipe, 8-Positive electrode return pipe, 9-Negative electrode return pipe, 10-Negative electrode air inlet valve, 101-First diaphragm, 102-First flow frame, 103-First electrode, 111-Second diaphragm, 112-Second flow frame, 113-Second electrode, 11- Negative electrode outlet valve, 12-negative electrode inlet pipe, 13-negative electrode outlet pipe, 301-negative electrode bypass pipe, 701-negative electrode bypass liquid inlet valve, 702-negative electrode liquid inlet valve, 901-negative electrode bypass liquid outlet valve, 902-negative electrode liquid outlet valve, 14-positive electrode inlet valve, 15-positive electrode outlet valve, 16-positive electrode inlet pipe, 17-positive electrode outlet pipe, 1201-air interface housing, 1202-porous diaphragm. Detailed Implementation

[0056] 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 a part of the embodiments of this application, and not all of them. 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.

[0057] The composition of an aqueous organic flow battery is shown in the attached figure. Figure 2 As shown, the flow battery stack 1 is the site of the electrochemical reaction. The positive electrolyte storage tank 2 holds the positive electrolyte, and the negative electrolyte storage tank 3 holds the negative electrolyte. The positive and negative circulation pumps 4 and 5 are used to transport the electrolyte. Electrolyte flowing from the positive electrolyte storage tank 2 is transported by the positive circulation pump 4, enters the flow battery stack 1 through the positive inlet pipe 6, and flows back to the positive electrolyte storage tank 2 through the positive return pipe 8 after exiting the flow battery stack 1. Electrolyte flowing from the negative electrolyte storage tank 3 is transported by the negative circulation pump 5, enters the flow battery stack 1 through the negative inlet pipe 7, and flows back to the negative electrolyte storage tank 3 through the negative return pipe 9 after exiting the flow battery stack 1.

[0058] As attached Figure 3 As shown, the battery stack 1 can employ a flow-through electrolyte flow method. The first electrode 103 can be a porous carbon material, embedded in the middle of the first liquid flow frame 102 (the flow channels and inlet / outlet details on the liquid flow frame are not shown in the figure). The first separator 101 can be an ion-exchange membrane or a porous membrane, used to separate the positive and negative electrodes of the battery. The electrolyte enters from the lower side of the first liquid flow frame 102, passes through the pores of the first electrode 103, gains and loses electrons at the electrode, undergoes an electrochemical reaction, and then flows out from the upper side of the first liquid flow frame 102. Alternatively, the flow battery stack 1 can employ a flow-by electrolyte flow method. The second electrode 113 can be a relatively dense carbon paper or carbon cloth, in contact with the surface of the second liquid flow frame 112 (the flow channels and inlet / outlet details on the liquid flow frame are not shown in the figure), rather than being embedded within the frame. The second separator 111 can be an ion-exchange membrane or a porous membrane, used to separate the positive and negative electrodes of the battery.

[0059] Example 1

[0060] This embodiment discloses an electrolyte rebalancing system for an aqueous organic flow battery, the structure of which is as follows: Figure 4 As shown, it includes an aqueous organic flow battery and an electrolyte rebalancing device, wherein the electrolyte rebalancing device is a negative electrode electrolyte rebalancing device.

[0061] The aqueous organic flow battery includes: a flow battery stack 1, a positive electrode electrolyte storage tank 2, a negative electrode electrolyte storage tank 3, a positive electrode circulation pump 4, a negative electrode circulation pump 5, a positive electrode inlet pipe 6, a positive electrode return pipe 8, a negative electrode inlet pipe 7, and a negative electrode return pipe 9; the outlet of the positive electrode electrolyte storage tank 2 is connected to the positive electrode electrolyte inlet of the flow battery stack 1 through the positive electrode inlet pipe 6, and the positive electrode circulation pump 4 is installed in the positive electrode inlet pipe 6; the positive electrode electrolyte outlet of the flow battery stack 1 is connected to the positive electrode return pipe. The positive electrode electrolyte storage tank 2 is connected to the inlet of the positive electrode electrolyte storage tank 2 via the negative electrode inlet pipe 7. The negative electrode inlet pipe 7 is equipped with a negative electrode circulation pump 5. The negative electrode electrolyte outlet of the flow battery stack 1 is connected to the inlet of the negative electrode electrolyte storage tank 3 via the negative electrode return pipe 9. The negative electrode electrolyte storage tank 3 is equipped with a pH detection structure. During the rebalancing operation, the pH value of the negative electrode electrolyte needs to be monitored to keep the pH value below 9.

[0062] The negative electrode electrolyte rebalancing device includes: a negative electrode inlet valve 10, a negative electrode outlet valve 11, a negative electrode inlet pipe 12, and a negative electrode outlet pipe 13; the negative electrode electrolyte storage tank 3 is connected to the negative electrode inlet pipe 12 near its outlet, and the negative electrode inlet pipe 12 is equipped with a negative electrode inlet valve 10. The negative electrode inlet pipe 12 is connected to an oxygen source, and oxygen is introduced into the negative electrode electrolyte storage tank 3 through the negative electrode inlet pipe to rebalance the electrolyte in the electrolyte storage tank that has an unbalanced capacity; the negative electrode electrolyte storage tank 3 is connected to the negative electrode outlet pipe 13 near its inlet, and the negative electrode outlet pipe 13 is equipped with a negative electrode outlet valve 11;

[0063] The negative electrode inlet pipe 7 and negative electrode return pipe 9 are made of materials permeable to oxygen, including but not limited to polyvinyl chloride (PVC), polyethylene (PE), and polypropylene (PP). Although the transmembrane permeation of active substances in the positive and negative electrolytes is slow, it continues throughout battery use. Therefore, the negative electrode inlet pipe 7 and negative electrode return pipe 9 can be made of materials with a certain oxygen permeability, allowing the battery to slowly rebalance during use, correcting capacity imbalances online, and minimizing maintenance costs.

[0064] The electrolyte rebalancing device further includes: a negative electrode bypass pipeline 301, a negative electrode bypass inlet valve 701, a negative electrode inlet valve 702, a negative electrode bypass outlet valve 901, and a negative electrode outlet valve 902.

[0065] The negative electrode inlet pipe 7 and the negative electrode return pipe 9 are connected by a negative electrode bypass pipe 301. A negative electrode bypass inlet valve 701 is provided in a section of the negative electrode bypass pipe 301 near the negative electrode inlet pipe 7, and a negative electrode bypass outlet valve 901 is provided in a section of the negative electrode bypass pipe 301 near the negative electrode return pipe 9. A negative electrode inlet valve 702 is provided in the negative electrode inlet pipe 7 between the negative electrode bypass pipe 301 and the negative electrode electrolyte inlet of the flow battery stack 1, and a negative electrode outlet valve 902 is provided in the negative electrode return pipe 9 between the negative electrode bypass pipe 301 and the negative electrode electrolyte outlet of the flow battery stack 1.

[0066] In this embodiment, the electrolyte rebalancing system of the aqueous organic flow battery uses a negative electrode inlet valve 10 and a negative electrode outlet valve 11 pre-installed below and above the negative electrode electrolyte storage tank 3, respectively. The negative electrode inlet valve 10 is connected to the negative electrode inlet pipe 12, and the negative electrode outlet valve 11 is connected to the negative electrode outlet pipe 13 to discharge unreacted gas from the storage tank. Gas can be supplied to the negative electrode storage tank using gas cylinders or by constructing an air supply source using an air compressor, steel pipes, valves, and gas hoses. Oxygen is the primary gas, with a purity of 1% to 100%. Other gas components can be any inert gas, such as helium, neon, or argon. During aeration, the negative electrode circulation pump 5 can be either on or off. When the negative electrode circulation pump 5 is on, the electrolyte can flow through the flow battery stack 1. Alternatively, a bypass pipe can be designed on the negative electrode inlet pipe 7 and the negative electrode return pipe 9 to prevent the electrolyte from flowing through the flow battery stack 1 during aeration. As attached Figure 4 As shown, close the negative electrode inlet valve 702 and the negative electrode outlet valve 902, open the negative electrode bypass inlet valve 701 and the negative electrode bypass outlet valve 901, and start the negative electrode circulation pump 5. The electrolyte bypasses the flow battery stack 1 and forms a circulation loop with the negative electrode electrolyte storage tank 3 through the negative electrode bypass pipeline 301. After the aeration is completed, close the negative electrode circulation pump 5, close the negative electrode bypass inlet valve 701 and the negative electrode bypass outlet valve 901, open the negative electrode inlet valve 702 and the negative electrode outlet valve 902, and start the negative electrode circulation pump 5. The electrolyte flows normally through the flow battery stack 1 and then returns to the negative electrode electrolyte storage tank 3.

[0067] The operating parameters for this embodiment are as follows:

[0068] The flow battery stack 1 adopts a flow-through electrolyte flow mode, with a rated power of 2.5kW. 1.5M 100L 4-(N,N,N-trimethyl)amine-2,2,6,6-tetramethylpiperidine-1-oxychloride is added to the positive electrode electrolyte storage tank 2, and 1.5M 100L N,N'-dimethyl-4,4'-bipyridine dichloride is added to the negative electrode electrolyte storage tank 3. [The last sentence appears to be incomplete and possibly refers to a different component.] Figure 4The rebalancing device in the battery has the following battery charging and discharging program settings:

[0069] (1) Charge at a constant power of 2.5kW until the voltage reaches 84V;

[0070] (2) Discharge at a constant power of 2.5kW until the voltage reaches 50.4V;

[0071] (3) Repeat steps (1) to (2) 100 times to continuously cycle the battery under rated power to obtain the battery capacity decay.

[0072] When the battery is charging or discharging, the negative electrode inlet valve 10, the negative electrode outlet valve 11, the negative electrode bypass liquid inlet valve 701, and the negative electrode bypass liquid outlet valve 901 are in the closed state.

[0073] Stop the charging / discharging process, turn off the positive electrode circulation pump 4 and the negative electrode circulation pump 5, connect the negative electrode inlet valve 10 and the negative electrode inlet pipe 12, and connect the negative electrode outlet valve 11 and the negative electrode outlet pipe 13, with air supplied by an air compressor. Adjust the negative electrode inlet valve 10 and the negative electrode outlet valve 11 to the open position, open the valve of the negative electrode inlet pipe 12, adjust the air intake rate to 20 ml / s, and allow ventilation for 2 hours. After ventilation is completed, close the valve of the negative electrode inlet pipe 12, and close the negative electrode inlet valve 10 and the negative electrode outlet valve 11. Throughout the process, monitor the pH of the negative electrode electrolyte and maintain it below 8.

[0074] Connect the negative electrode inlet pipe 12 to the nitrogen cylinder, open the negative electrode inlet valve 10 and the negative electrode outlet valve 11, open the nitrogen cylinder, and use nitrogen to replace the air in the negative electrode electrolyte storage tank. After 30 minutes, the replacement is completed, and the valves of the nitrogen cylinder, negative electrode inlet valve 10 and negative electrode outlet valve 11 are closed.

[0075] The battery then operates according to the following charging and discharging procedure:

[0076] (1) Charge at a constant power of 2.5kW until the voltage reaches 84V;

[0077] (2) Discharge at a constant power of 2.5kW until the voltage reaches 50.4V;

[0078] (3) Repeat steps (1) to (2) for 5 cycles and record the battery discharge capacity.

[0079] Appendix Figure 7The changes in battery discharge capacity before and after the rebalancing operation are illustrated. Before air was introduced into the negative electrolyte tank, the battery underwent charge-discharge cycles at a constant power of 2.5kW. After 100 cycles, the battery capacity showed some degradation. After air was introduced into the negative electrolyte tank, the battery was cycled again under the same charge-discharge conditions. The battery discharge capacity recovered to a level comparable to that of the first cycle, indicating that the introduction of air effectively restored the battery capacity.

[0080] Example 2

[0081] This embodiment discloses an electrolyte rebalancing system for an aqueous organic flow battery, the structure of which is as follows: Figure 5 As shown, it includes an aqueous organic flow battery and an electrolyte rebalancing device. The aqueous organic flow battery is the same as in Example 1, and the electrolyte rebalancing device is a positive electrode electrolyte rebalancing device.

[0082] The positive electrode electrolyte rebalancing device includes: a positive electrode inlet valve 14, a positive electrode outlet valve 15, a positive electrode inlet pipeline 16, and a positive electrode outlet pipeline 17; the positive electrode electrolyte storage tank 2 is connected to the positive electrode inlet pipeline 16, the positive electrode inlet pipeline 16 is provided with the positive electrode inlet valve 14, and the positive electrode inlet pipeline 16 is connected to an oxygen source; the positive electrode electrolyte storage tank 2 is connected to the positive electrode outlet pipeline 17, and the positive electrode outlet pipeline 17 is provided with the positive electrode outlet valve 15.

[0083] Unlike Example 1, where air / oxygen is directly introduced from the negative electrode electrolyte storage tank 3, in Example 2, air / oxygen is introduced from the positive electrode electrolyte storage tank 2, and the air / oxygen permeates through the separator of the battery stack into the negative electrode electrolyte storage tank 3. (See attached diagram) Figure 5 As shown, a positive electrode inlet valve 14 and a positive electrode outlet valve 15 are respectively pre-installed below and above the positive electrode electrolyte storage tank 2. The positive electrode inlet valve 14 is connected to the positive electrode inlet pipeline 16, and the positive electrode outlet valve 15 is connected to the positive electrode outlet pipeline 17 to discharge unreacted gas from the storage tank. The airflow rate into the positive electrode inlet pipeline 17 and the negative electrode inlet pipeline 12 can be adjusted by a pressure reducing valve, or by an attached... Figure 6 The interface shown is used to further fine-tune the airflow rate. 1201 is the housing of the air interface, used to fix and seal the porous diaphragm 1202. One end is connected to the negative intake valve 10, and the other end is connected to the negative intake pipe 12. Adjusting the pore size of the porous diaphragm 1202 can fine-tune the airflow rate.

[0084] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this utility model, and are not intended to limit it. Although the utility model 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 the embodiments of this utility model.

Claims

1. An electrolyte rebalancing system for aqueous organic flow batteries, characterized in that, The water-based organic liquid flow battery and electrolyte rebalancing device are provided. The water-based organic liquid flow battery comprises a liquid flow battery stack (1), a positive electrolyte storage tank (2), a negative electrolyte storage tank (3), a positive circulating pump (4), a negative circulating pump (5), a positive liquid inlet pipeline (6), a positive liquid return pipeline (8), a negative liquid inlet pipeline (7) and a negative liquid return pipeline (9); the outlet of the positive electrolyte storage tank (2) is communicated with the positive electrolyte inlet of the liquid flow battery stack (1) through the positive liquid inlet pipeline (6), and the positive circulating pump (4) is arranged in the positive liquid inlet pipeline (6); the positive electrolyte outlet of the liquid flow battery stack (1) is communicated with the inlet of the positive electrolyte storage tank (2) through the positive liquid return pipeline (8); the outlet of the negative electrolyte storage tank (3) is communicated with the negative electrolyte inlet of the liquid flow battery stack (1) through the negative liquid inlet pipeline (7), and the negative circulating pump (5) is arranged in the negative liquid inlet pipeline (7); and the negative electrolyte outlet of the liquid flow battery stack (1) is communicated with the inlet of the negative electrolyte storage tank (3) through the negative liquid return pipeline (9). The electrolyte rebalancing device comprises a negative electrolyte rebalancing device and / or a positive electrolyte rebalancing device. The negative electrolyte rebalancing device comprises a negative gas inlet valve (10), a negative gas outlet valve (11), a negative gas inlet pipeline (12) and a negative gas outlet pipeline (13); the negative electrolyte storage tank (3) is communicated with the negative gas inlet pipeline (12), the negative gas inlet valve (10) is arranged in the negative gas inlet pipeline (12), and the negative gas inlet pipeline (12) is communicated with an oxygen source; and the negative electrolyte storage tank (3) is communicated with the negative gas outlet pipeline (13), and the negative gas outlet valve (11) is arranged in the negative gas outlet pipeline (13). The positive electrolyte rebalancing device comprises a positive gas inlet valve (14), a positive gas outlet valve (15), a positive gas inlet pipeline (16) and a positive gas outlet pipeline (17); the positive electrolyte storage tank (2) is communicated with the positive gas inlet pipeline (16), the positive gas inlet valve (14) is arranged in the positive gas inlet pipeline (16), and the positive gas inlet pipeline (16) is communicated with an oxygen source; and the positive electrolyte storage tank (2) is communicated with the positive gas outlet pipeline (17), and the positive gas outlet valve (15) is arranged in the positive gas outlet pipeline (17).

2. The electrolyte rebalancing system of the aqueous organic flow battery of claim 1, wherein, The liquid flow battery stack (1) is a flow-through electrolyte flow structure or a flow-by electrolyte flow structure.

3. The electrolyte rebalancing system of the aqueous organic flow battery of claim 1, wherein, The positive liquid inlet pipeline (6), the positive liquid return pipeline (8), the negative liquid inlet pipeline (7) and the negative liquid return pipeline (9) are plastic pipelines.

4. The electrolyte rebalancing system of the aqueous organic flow battery of claim 1, wherein, The positive liquid inlet pipeline (6), the positive liquid return pipeline (8), the negative liquid inlet pipeline (7) and the negative liquid return pipeline (9) are pipelines made of oxygen-permeable materials.

5. The electrolyte rebalancing system of the aqueous organic flow battery of claim 1, wherein, The negative electrolyte storage tank (3) is communicated with the negative gas inlet pipeline (12) on one side close to the outlet thereof; and the negative electrolyte storage tank (3) is communicated with the negative gas outlet pipeline (13) on one side close to the inlet thereof.

6. The electrolyte rebalancing system of the aqueous organic flow battery of claim 1, wherein, The positive electrolyte storage tank (2) is communicated with the positive gas inlet pipeline (16) on the side close to the outlet thereof; and the positive electrolyte storage tank (2) is communicated with the positive gas outlet pipeline (17) on the side close to the inlet thereof.

7. The electrolyte rebalancing system of the aqueous organic flow battery of claim 1, wherein, The negative electrolyte rebalancing device further comprises a negative bypass pipeline (301), a negative bypass liquid inlet valve (701), a negative liquid inlet valve (702), a negative bypass liquid outlet valve (901) and a negative liquid outlet valve (902). The negative liquid inlet pipeline (7) and the negative liquid return pipeline (9) are communicated through the negative bypass pipeline (301), the negative bypass pipeline (301) is provided with the negative bypass liquid inlet valve (701) in the section close to the negative liquid inlet pipeline (7), the negative bypass pipeline (301) is provided with the negative bypass liquid outlet valve (901) in the section close to the negative liquid return pipeline (9), the negative liquid inlet pipeline (7) between the negative bypass pipeline (301) and the negative electrolyte inlet of the flow battery stack (1) is provided with the negative liquid inlet valve (702), and the negative liquid return pipeline (9) between the negative bypass pipeline (301) and the negative electrolyte outlet of the flow battery stack (1) is provided with the negative liquid outlet valve (902).

8. The electrolyte rebalancing system of the aqueous organic flow battery of claim 1, wherein, The positive electrolyte rebalancing device further comprises a positive bypass pipeline, a positive bypass liquid inlet valve, a positive liquid inlet valve, a positive bypass liquid outlet valve and a positive liquid outlet valve. The positive liquid inlet pipeline and the positive liquid return pipeline are communicated through the positive bypass pipeline, the positive bypass pipeline is provided with the positive bypass liquid inlet valve in the section close to the positive liquid inlet pipeline, the positive bypass pipeline is provided with the positive bypass liquid outlet valve in the section close to the positive liquid return pipeline, the positive liquid inlet pipeline between the positive bypass pipeline and the positive electrolyte inlet of the flow battery stack is provided with the positive liquid inlet valve, and the positive liquid return pipeline between the positive bypass pipeline and the positive electrolyte outlet of the flow battery stack is provided with the positive liquid outlet valve.

9. The electrolyte rebalancing system of the aqueous organic flow battery of claim 1, wherein, The negative electrolyte storage tank (3) is provided with a pH value detection structure.

10. The electrolyte rebalancing system of the aqueous organic flow battery of claim 1, wherein, The positive electrolyte storage tank (2) is provided with a pH value detection structure.

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