A vanadium redox flow battery and a method of protecting it when stopped

Abstract

The application provides a full vanadium liquid flow battery and a protection method thereof when stopping operation, and belongs to the technical field of methods or devices for directly converting chemical energy into electric energy, wherein the full vanadium liquid flow battery comprises a positive electrode circulation system and a negative electrode circulation system; the positive electrode circulation system comprises a positive electrode storage tank, a positive electrode pump and a positive electrode half cell; and the negative electrode circulation system comprises a negative electrode storage tank, a negative electrode pump and a negative electrode half cell; the full vanadium liquid flow battery of the application can isolate the negative electrode storage tank by arranging valves at the inlet and outlet of the negative electrode storage tank; the negative electrode circulation system and the positive electrode storage tank are communicated through a first communication pipeline and a second communication pipeline; when the full vanadium liquid flow battery stops operation, the positive electrode electrolyte in the positive electrode storage tank can be guided into the negative electrode circulation system, so that the negative electrode electrolyte in the negative electrode circulation system is mixed, thereby avoiding the problem that the negative electrode electrolyte is precipitated in solid form due to a low-temperature environment, and the negative electrode circulation system is effectively protected.

Description

Technical Field

[0001] This invention relates to the field of methods or apparatus for directly converting chemical energy into electrical energy, and more specifically to a vanadium redox flow battery and a protection method thereon when the battery is not in operation. Background Technology

[0002] Vanadium redox flow batteries (VFBs) have become one of the most promising technologies for large-scale energy storage in renewable energy generation, grid peak shaving and valley filling, emergency and backup power plants due to their outstanding advantages such as independent and adjustable system capacity and power, rapid response, safety and reliability, environmental friendliness, long cycle life, and easy maintenance and regeneration.

[0003] Electrolyte is a crucial component of VFB (Vacuum-Based Battery), and its concentration and volume directly determine the battery's capacity. The stability of the electrolyte directly impacts the reliability and stability of the VFB during long-term operation. However, in practice, the solubility and stability of vanadium ions in the supporting electrolyte are limited. For example, when the VFB system is running stably, the electrolyte temperature will not fall below 20°C. When the VFB system is shut down and the ambient temperature is low, the electrolyte temperature will continue to drop. When the temperature drops to a certain threshold, low-valence vanadium ions in the negative electrode electrolyte are prone to precipitate as solids, causing damage to the battery and piping, thus affecting the practical application of the VFB system.

[0004] In existing technologies, while the deposition of low-valence vanadium ions in the electrolyte can be addressed by adding small amounts of additives to improve the low-temperature stability of these ions, allowing them to remain stable at lower temperatures, this method only stabilizes the negative electrode electrolyte for a few hours. If the low-temperature period is prolonged, solid deposition will still occur. Therefore, it is urgent to address the potential damage to the system caused by the negative electrode electrolyte under low-temperature conditions, especially for VFB systems operating in extremely cold regions. Summary of the Invention

[0005] Therefore, the technical problem to be solved by the present invention is to overcome the defect of the existing vanadium redox flow battery that cannot maintain stability when it stops operating at a low temperature, thereby providing a vanadium redox flow battery and a protection method thereon when it stops operating.

[0006] To solve the above-mentioned technical problems, the present invention provides a vanadium redox flow battery, comprising: a positive electrode circulation system and a negative electrode circulation system, wherein the positive electrode circulation system comprises: a positive electrode storage tank, a positive electrode pump and a positive electrode half-cell, and the negative electrode circulation system comprises: a negative electrode storage tank, a negative electrode pump and a negative electrode half-cell;

[0007] The negative electrode storage tank is equipped with a liquid outlet valve at its outlet and a liquid return valve at its reflux outlet.

[0008] The outlet pipe of the liquid outlet valve is connected to the outlet of the positive electrode storage tank via a first connecting pipe, and the inlet pipe of the liquid return valve is connected to the inlet of the positive electrode storage tank via a second connecting pipe.

[0009] A first isolation valve is installed on the first connecting pipe, and a second isolation valve is installed on the second connecting pipe.

[0010] Optionally, one end of the first connecting pipe is connected to the positive electrolyte pipe between the positive electrode storage tank and the positive electrode pump via a first tee.

[0011] Optionally, one end of the second connecting pipe is connected to the positive electrolyte pipe between the positive electrode storage tank and the positive electrode half-cell via a second tee.

[0012] Optionally, one end of the first connecting pipe and one end of the second connecting pipe are respectively connected to the negative electrode circulation system via a three-way valve.

[0013] Optionally, the first isolation valve is located at one end of the first connecting pipe near the negative electrode circulation system, and the second isolation valve is located at one end of the second connecting pipe near the negative electrode circulation system.

[0014] Optionally, a temperature sensor is provided in the negative electrode circulation system.

[0015] Optionally, the temperature sensor is disposed on the outlet pipe of the negative electrode half-cell.

[0016] Optionally, the first isolation valve and the second isolation valve are electrically controlled valves.

[0017] Optionally, the outlet valve and the return valve are electrically controlled valves.

[0018] Optionally, it further includes: a controller, which is electrically connected to the negative electrode pump, the temperature sensor, the first isolation valve, the second isolation valve, the outlet valve, and the return valve, respectively.

[0019] The present invention also provides a protection method for a vanadium redox flow battery as described in any of the above-mentioned solutions when it is stopped from operation, characterized by comprising the following steps:

[0020] When the vanadium redox flow battery is not in operation, close the outlet valve and return valve of the negative electrode storage tank;

[0021] Then open the first isolation valve on the first connecting pipe and the second isolation valve on the second connecting pipe;

[0022] Start the negative electrode pump to guide the positive electrode electrolyte from the positive electrode tank to the negative electrode electrolyte pipeline and the negative electrode half cell;

[0023] Once the negative electrode electrolyte pipe and the negative electrode half-cell are filled with positive electrode electrolyte, turn off the negative electrode pump.

[0024] The technical solution of this invention has the following advantages:

[0025] 1. The vanadium redox flow battery provided by the present invention isolates the negative electrode tank by setting valves at the inlet and outlet of the negative electrode tank. Then, through the first and second connecting pipes, other equipment and pipes in the negative electrode circulation system are connected to the positive electrode tank. Thus, when the vanadium redox flow battery stops operating, the positive electrode electrolyte in the positive electrode tank can be guided to the negative electrode circulation system to mix the negative electrode electrolyte in the negative electrode circulation system. This avoids the problem of solid precipitation of the negative electrode electrolyte due to the low temperature environment and effectively protects the negative electrode circulation system.

[0026] 2. The protection method for the vanadium redox flow battery provided by the present invention during shutdown can mix the positive electrolyte in the positive electrode storage tank into other equipment in the negative electrode circulation system by opening and closing valves and driving the negative electrode pump. This avoids the problem of damage to the pipelines and equipment in the negative electrode circulation system caused by the precipitation of solids from the negative electrolyte due to low ambient temperature. Attached Figure Description

[0027] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0028] Figure 1 This is a schematic diagram of one embodiment of the all-vanadium redox flow battery provided in the embodiments of the present invention.

[0029] Explanation of reference numerals in the attached figures:

[0030] 1. Positive electrode storage tank; 2. Positive electrode pump; 3. Positive electrode half-cell; 4. Negative electrode storage tank; 5. Negative electrode pump; 6. Negative electrode half-cell; 7. Discharge valve; 8. Return valve; 9. First connecting pipe; 10. Second connecting pipe; 11. First isolation valve; 12. Second isolation valve; 13. First tee; 14. Second tee; 15. Third tee; 16. Fourth tee; 17. Temperature sensor. Detailed Implementation

[0031] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0032] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0033] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0034] Furthermore, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0035] like Figure 1 The diagram illustrates a specific implementation of the vanadium redox flow battery provided in this embodiment, comprising a positive electrode circulation system and a negative electrode circulation system. The positive electrode circulation system includes a positive electrode storage tank 1, a positive electrode pump 2, and a positive electrode half-cell 3. The negative electrode circulation system includes a negative electrode storage tank 4, a negative electrode pump 5, and a negative electrode half-cell 6. In the positive electrode circulation system, the positive electrode electrolyte, driven by the positive electrode pump 2, flows from the positive electrode storage tank 1 through the positive electrode pump 2 to the positive electrode half-cell 3, and then flows back from the positive electrode half-cell 3 to the positive electrode storage tank 1. In the negative electrode circulation system, the negative electrode electrolyte, driven by the negative electrode pump 5, flows from the negative electrode storage tank 4 through the negative electrode pump 5 to the negative electrode half-cell 6, and then flows back from the negative electrode half-cell 6 to the negative electrode storage tank 4.

[0036] like Figure 1As shown, in the vanadium redox flow battery provided in this embodiment, the outlet of the negative electrode storage tank 4 is equipped with an outlet valve 7, and the return outlet of the negative electrode storage tank 4 is equipped with a return valve 8. When the outlet valve 7 and the return valve 8 are closed, the negative electrode storage tank 4 can be isolated from the negative electrode circulation system, thereby facilitating the flushing of other equipment in the negative electrode circulation system.

[0037] like Figure 1 As shown, in the vanadium redox flow battery provided in this embodiment, the outlet pipe of the outlet valve 7 is connected to the outlet of the positive electrode tank 1 through the first connecting pipe 9, and the inlet pipe of the return valve 8 is connected to the inlet of the positive electrode tank 1 through the second connecting pipe 10. This allows the positive electrode tank 1 to flush the pipes, negative electrode pump 5, and negative electrode half-cell 6 in the negative electrode circulation system when the battery stops running, thereby mixing the positive electrode electrolyte with the negative electrode electrolyte in the negative electrode circulation system and avoiding the problem of solid precipitation of the negative electrode electrolyte at long-term low temperature.

[0038] like Figure 1 As shown, in the vanadium redox flow battery provided in this embodiment, a first isolation valve 11 is provided on the first connecting pipe 9, and a second isolation valve 12 is provided on the second connecting pipe 10. When the battery is working normally, by closing the first isolation valve 11 and the second isolation valve 12, the positive electrode circulation system and the negative electrode circulation system can be ensured to operate independently without interference.

[0039] like Figure 1 As shown, in the vanadium redox flow battery provided in this embodiment, one end of the first connecting pipe 9 is connected to the positive electrolyte pipeline between the positive electrode storage tank 1 and the positive electrode pump 2 via the first tee 13. When the battery stops operating, the outlet valve 7 and return valve 8 are closed, the first isolation valve 11 and the second isolation valve 12 are opened, and then the positive electrode pump 2 and the negative electrode pump 5 are started simultaneously. This allows the positive electrolyte in the positive electrode storage tank 1 to be diverted within the pipeline, with part entering the direction of the positive electrode pump 2 and part entering the direction of the negative electrode circulation system. This allows the positive electrolyte to circulate in the negative electrode circulation system in other equipment besides the negative electrode storage tank 4, thereby mixing the negative electrolyte in the negative electrode circulation system with the positive electrolyte, avoiding the problem of residual negative electrolyte in the negative electrode circulation system precipitating solids and damaging the equipment in a long-term low-temperature environment. In addition, as an alternative implementation, one end of the first connecting pipe 9 can also extend directly into the positive electrode storage tank 1.

[0040] like Figure 1As shown, in the vanadium redox flow battery provided in this embodiment, one end of the second connecting pipe 10 is connected to the positive electrolyte pipe between the positive electrode storage tank 1 and the positive electrode half-cell 3 via a second tee 14. With this configuration, when the positive electrolyte flows out of the negative electrode circulation system, it will mix with the positive electrolyte flowing out of the positive electrode circulation system in the pipe before flowing back to the positive electrode storage tank 1, and then both will flow back into the positive electrode storage tank 1. Alternatively, as an alternative implementation, the second connecting pipe 10 can also lead directly to the positive electrode storage tank 1.

[0041] like Figure 1 As shown, in the vanadium redox flow battery provided in this embodiment, the other end of the first connecting pipe 9 is connected to the negative electrolyte pipe between the outlet valve 7 and the negative electrode pump 5 via a third three-way valve 15. The other end of the second connecting pipe 10 is connected to the negative electrolyte pipe between the return valve 8 and the negative electrode half-cell 6 via a fourth three-way valve 16. Alternatively, as an alternative implementation, the third three-way valve 15 and the fourth three-way valve 16 can be three-way valves, controlling the opening and closing of the two paths to prevent excessive negative electrolyte from entering the first connecting pipe 9 and the second connecting pipe 10 during normal battery operation. Alternatively, as an alternative implementation, the first isolation valve 11 and the second isolation valve 12 can be located at the end of the first connecting pipe 9 and the second connecting pipe 10 closer to the negative electrode circulation system to prevent excessive negative electrode electrolyte from entering the pipes during normal battery operation.

[0042] like Figure 1 As shown, in the vanadium redox flow battery provided in this embodiment, a temperature sensor 17 is provided in the negative electrode circulation system. This temperature sensor 17 allows for real-time monitoring of the temperature in the negative electrode circulation system when the battery is shut down, thereby determining whether to initiate a flushing operation. Alternatively, as an alternative implementation, the temperature sensor 17 can be omitted, and the decision to initiate the flushing operation can be based on changes in external temperature and experience.

[0043] like Figure 1 As shown, in the vanadium redox flow battery provided in this embodiment, the temperature sensor 17 is installed on the outlet pipe of the negative electrode half-cell 6. This location is the return pipe of the negative electrode half-cell 6, and it can accurately detect the lowest temperature in the negative electrode circulation system, thus providing a basis for determining whether to initiate the flushing process. Alternatively, as an alternative implementation, the temperature sensor 17 can be installed on any section of the pipe in the negative electrode system.

[0044] like Figure 1As shown, in the vanadium redox flow battery provided in this embodiment, the outlet valve 7 and the return valve 8 are electrically controlled valves, such as solenoid valves, which can be operated remotely. Alternatively, as an alternative implementation, the outlet valve 7 and the return valve 8 can also be manual valves.

[0045] like Figure 1 As shown, in the vanadium redox flow battery provided in this embodiment, the first isolation valve 11 and the second isolation valve 12 are electrically controlled valves, such as solenoid valves, which can be operated remotely. Alternatively, as an alternative implementation, the first isolation valve 11 and the second isolation valve 12 can also be manual valves.

[0046] like Figure 1 As shown, in the vanadium redox flow battery provided in this embodiment, when the outlet valve 7, the return valve 8, the first isolation valve 11, and the second isolation valve 12 are all electrically controlled valves, a controller is also included. The controller is electrically connected to the negative electrode pump 5, the temperature sensor 17, the first isolation valve 11, the second isolation valve 12, the outlet valve 7, and the return valve 8, respectively. When the battery is in a shutdown state, when the temperature sensor 17 detects that the temperature in the negative electrode circulation system is lower than a set temperature threshold, the controller receives the signal from the temperature sensor 17, then controls the outlet valve 7 and the return valve 8 to close, and controls the first isolation valve 11 and the second isolation valve 12 to open, and then controls the negative electrode pump 5 to start, so that the positive electrode electrolyte fills the pipes and equipment in the negative electrode circulation system, thereby mixing the negative electrode electrolyte in the negative electrode circulation system and avoiding the problem of solid precipitation of the negative electrode electrolyte under long-term low-temperature environment.

[0047] It should be noted that the set temperature threshold is higher than the crystallization temperature of the negative electrode electrolyte. Preferably, the set temperature threshold is 0.1-5℃ higher than the crystallization temperature of the negative electrode electrolyte, and more preferably 0.5-2℃ higher than the crystallization temperature of the negative electrode electrolyte.

[0048] The protection method for a vanadium redox flow battery provided in this embodiment during shutdown includes the following steps:

[0049] When the vanadium redox flow battery is not in operation, close the outlet valve 7 and return valve 8 of the negative electrode storage tank 4 to isolate the negative electrode storage tank 4 from other equipment in the negative electrode circulation system.

[0050] Then, the first isolation valve 11 on the first connecting pipe 9 and the second isolation valve 12 on the second connecting pipe 10 are opened, thereby forming a circulation channel between the other equipment in the negative electrode circulation system and the positive electrode storage tank 1.

[0051] Start the negative electrode pump 5 to guide the positive electrode electrolyte from the positive electrode storage tank 1 to the negative electrode electrolyte pipeline and the negative electrode half-cell 6, so that the positive electrode electrolyte fills the equipment and pipelines in the negative electrode circulation system, and the negative electrode electrolyte in the equipment and pipelines in the negative electrode circulation system is mixed with the positive electrode electrolyte, thereby avoiding the problem that the negative electrode electrolyte is prone to solid precipitation under long-term low temperature environment.

[0052] Once the negative electrode electrolyte pipeline and the negative electrode half-cell 6 are filled with positive electrode electrolyte, the negative electrode pump 5 is turned off. This facilitates long-term storage of the battery as a whole and prevents internal damage due to excessively low ambient temperatures. Specifically, the valence state of the electrolyte in the pipeline at the outlet of the negative electrode half-cell 6 can be determined by detecting this state. The electrolyte at the outlet of the negative electrode half-cell 6 must not contain divalent or trivalent vanadium ions; that is, once divalent and / or trivalent vanadium ions are absent, the negative electrode circulation pump can be turned off.

[0053] It should be noted that the above method is applicable to an ambient temperature range between the negative electrode electrolyte crystallization temperature and the positive electrode electrolyte crystallization temperature.

[0054] The negative electrode electrolyte comprises a total vanadium ion concentration of 1-3 mol / L and a hydrogen ion concentration of 1-10 mol / L, wherein the vanadium ions are divalent and / or trivalent, and its crystallization temperature is from 10°C to -20°C.

[0055] The positive electrode electrolyte composition includes a total vanadium ion concentration of 1-3 mol / L and a hydrogen ion concentration of 1-10 mol / L, wherein the vanadium ion valence state is tetravalent and / or pentavalent, and its crystallization temperature is -21℃ to -60℃.

[0056] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A vanadium redox flow battery, characterized in that, include: A positive electrode circulation system, a negative electrode circulation system and a controller, wherein the positive electrode circulation system includes: a positive electrode storage tank (1), a positive electrode pump (2) and a positive electrode half-cell (3), and the negative electrode circulation system includes: a negative electrode storage tank (4), a negative electrode pump (5), a negative electrode half-cell (6) and a temperature sensor (17). The negative electrode storage tank (4) is provided with a liquid outlet valve (7) at its outlet and a liquid return valve (8) at its return outlet. The outlet pipe of the liquid outlet valve (7) is connected to the outlet of the positive electrode storage tank (1) through the first connecting pipe (9), and the inlet pipe of the liquid return valve (8) is connected to the inlet of the positive electrode storage tank (1) through the second connecting pipe (10). A first isolation valve (11) is provided on the first connecting pipe (9), and a second isolation valve (12) is provided on the second connecting pipe (10). The liquid outlet valve (7), the liquid return valve (8), the first isolation valve (11), and the second isolation valve (12) are electrically controlled valves. The controller is electrically connected to the negative electrode pump (5), the temperature sensor (17), the first isolation valve (11), the second isolation valve (12), the liquid outlet valve (7), and the liquid return valve (8), respectively. When the battery is in a shutdown state, when the temperature sensor (17) detects that the temperature in the negative electrode circulation system is lower than the set temperature threshold, the controller receives the signal from the temperature sensor (17), then controls the liquid outlet valve (7) and the liquid return valve (8) to close, and controls the first isolation valve (11) and the second isolation valve (12) to open, and then controls the negative electrode pump (5) to start. The set temperature threshold is higher than the crystallization temperature of the negative electrode electrolyte.

2. The all-vanadium redox flow battery according to claim 1, characterized in that, One end of the first connecting pipe (9) is connected to the positive electrolyte pipe between the positive electrode storage tank (1) and the positive electrode pump (2) via the first tee (13).

3. The all-vanadium redox flow battery according to claim 2, characterized in that, One end of the second connecting pipe (10) is connected to the positive electrolyte pipe between the positive electrode storage tank (1) and the positive electrode half cell (3) via the second tee (14).

4. The all-vanadium redox flow battery according to claim 1, characterized in that, One end of the first connecting pipe (9) and the second connecting pipe (10) are respectively connected to the negative electrode circulation system through a three-way valve.

5. The all-vanadium redox flow battery according to claim 1, characterized in that, The first isolation valve (11) is located at one end of the first connecting pipe (9) near the negative electrode circulation system, and the second isolation valve (12) is located at one end of the second connecting pipe (10) near the negative electrode circulation system.

6. A protection method for a vanadium redox flow battery according to any one of claims 1-5 during shutdown, characterized in that, Includes the following steps: When the vanadium redox flow battery is not in operation, close the outlet valve (7) and return valve (8) of the negative electrode storage tank (4). Then open the first isolation valve (11) on the first connecting pipe (9) and the second isolation valve (12) on the second connecting pipe (10). Start the negative electrode pump (5) to guide the positive electrode electrolyte from the positive electrode tank (1) to the negative electrode electrolyte pipeline and the negative electrode half cell (6); After the negative electrode electrolyte pipe and the negative electrode half cell (6) are filled with positive electrode electrolyte, the negative electrode pump (5) is turned off.

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