Recovery device for residual electrolyte of vanadium redox flow battery stack

Abstract

The invention discloses a recovery device for residual electrolyte of a vanadium redox flow battery stack, which relates to the technical field of battery equipment, and comprises a stack group system, a positive electrode circulating pipeline, a negative electrode circulating pipeline, a positive electrode circulating pipeline, a negative electrode circulating pipeline, a positive electrode circulating pipeline and a negative electrode circulating pipeline, a positive electrode liquid tank and a first circulating pump are connected to the positive electrode circulating pipeline in series; the positive electrode collecting tank is connected in parallel inside or outside the positive electrode circulating pipeline, and the positive electrode collecting tank is communicated with the positive electrode circulating pipeline; the negative electrode circulation pipeline is connected with the electric pile group system, and a negative electrode liquid tank and a second circulation pump are connected to the negative electrode circulation pipeline in series; the negative electrode collecting tank is connected in parallel inside or outside the negative electrode circulating pipeline, and the negative electrode collecting tank is communicated with the negative electrode circulating pipeline; the positive electrode circulation pipeline and the negative electrode circulation pipeline are provided with control valve sets. The invention has reasonable design structure, can reduce the occurrence of the self-discharge phenomenon of the battery, and prolongs the service life of the electric pile.

Description

Technical Field

[0001] The invention relates to the technical field of battery equipment, in particular to a device for recovering residual electrolyte of a vanadium liquid flow battery stack. Background Art

[0002] With the continuous implementation of the dual-carbon policy, the development of new energy has made great progress. Emerging energy is composed of a variety of structures, among which the energy storage structure plays an important role and can collect and store related energy. Among them, the energy storage structure is preferably a vanadium liquid flow battery. Vanadium liquid flow batteries have inherent safety, expandable capacity and a long practical life. Therefore, they are the preferred choice for long-term energy storage.

[0003] The vanadium liquid flow battery system includes a variety of structures, including a stack. The stack is like a liquid storage container. A certain amount of electrolyte will remain inside the stack chamber. Especially when the vanadium battery system has completed power storage, the electrolyte remaining in the positive and negative chambers of the stack is mostly in the state of divalent and pentavalent vanadium ions. Since divalent and pentavalent vanadium ions cannot coexist, they shuttle through the diaphragm and react to generate heat, causing the temperature inside the stack to rise, thereby affecting the service life of the stack and the attenuation of the battery capacity. This is called the self-discharge phenomenon of the battery. In the prior art, in order to reduce the frequency of battery self-discharge, the battery stack is usually placed high and the electrolyte tank is placed low in the battery system layout. When the system stops, the electrolyte in the battery stack flows back to the positive and negative electrode storage tanks under the action of gravity, so as to achieve the purpose of reducing self-discharge.

[0004] The high arrangement of the battery stack will cause the complexity of the system layout, which will increase the system cost. The height of the liquid tank is limited by the position of the battery stack, and the size of the liquid tank determines the size of the battery capacity. Therefore, the limited height of the liquid tank will inevitably lead to the limited volume of the liquid tank, which will cause certain difficulties in capacity expansion. Summary of the invention

[0005] 1) Technical issues solved The purpose of the present invention is to make up for the deficiencies of the prior art and to provide a device for recovering residual electrolyte in a vanadium liquid flow battery stack.

[0006] 2) Technical solution

[0007] To achieve the above object, the present invention provides the following technical solution: a device for recovering residual electrolyte of a vanadium liquid flow battery stack, comprising a stack group system, characterized in that the stack group system is equipped with a positive electrode recovery system and a negative electrode recovery system in parallel; The positive electrode recovery system comprises: A positive electrode circulation pipeline, the positive electrode circulation pipeline is in communication with the battery stack system, a positive electrode liquid tank and a first circulation pump are connected in series to the positive electrode circulation pipeline, and a liquid outlet of the first circulation pump is connected to a liquid inlet of the battery stack system; A positive electrode collection tank, which can be connected in parallel to the inside or outside of the positive electrode circulation pipeline, and the positive electrode collection tank is in communication with the positive electrode circulation pipeline; The negative electrode recovery system comprises: A negative electrode circulation pipeline, the negative electrode circulation pipeline is in communication with the battery stack system, the negative electrode circulation pipeline is connected in series with a negative electrode liquid tank and a second circulation pump, and a liquid outlet of the second circulation pump is connected to a liquid inlet of the battery stack system; A negative electrode collection tank, which can be connected in parallel to the inside or outside of the negative electrode circulation pipeline, and the negative electrode collection tank is in communication with the negative electrode circulation pipeline; The positive electrode circulation pipeline and the negative electrode circulation pipeline are configured with a control valve group, and the control valve group is used to control the connection between the positive electrode recovery system and the negative electrode recovery system and the fuel cell stack system.

[0008] Further, when the positive electrode collection tank is connected in parallel to the positive electrode circulation pipeline, the positive electrode collection tank is equipped with a third connecting pipe, one end of the third connecting pipe is connected to the positive electrode liquid tank, and the other end is connected to the connecting pipeline between the first circulation pump and the stack system; When the negative electrode collection tank is connected in parallel to the negative electrode circulation pipeline, the negative electrode collection tank is equipped with a sixth connecting pipe, one end of which is connected to the negative electrode liquid tank, and the other end is connected to the connecting pipeline between the second circulation pump and the battery stack system.

[0009] Further, when the positive electrode collection tank is connected in parallel to the positive electrode circulation pipeline, the control valve group includes a first valve, a second valve and a seventh valve, and the first valve and the second valve are respectively located at a side of the liquid inlet and the liquid outlet of the first circulation pump away from the third connecting pipe; The seventh valve is installed on the third connecting pipe; When the negative electrode collection tank is connected in parallel to the negative electrode circulation pipeline, the control valve group includes a third valve, a fourth valve and a tenth valve, and the third valve and the fourth valve are respectively located at a side of the liquid inlet and the liquid outlet of the second circulation pump away from the sixth connecting pipe; The tenth valve is installed on the sixth connecting pipe.

[0010] Further, when the positive electrode collection tank is connected in parallel to the positive electrode circulation pipeline, the positive electrode collection tank is connected to the positive electrode liquid tank, the positive electrode recovery tank is connected in series with a third circulation pump, and the control valve group includes an eleventh valve and a twelfth valve, the eleventh valve is installed on the side of the positive electrode collection tank close to the stack system, and the twelfth valve is installed between the third circulation pump and the positive electrode liquid tank; When the negative electrode collecting tank is connected in parallel to the outside of the negative electrode circulation pipeline, the negative electrode collecting tank is connected to the negative electrode liquid tank, the negative electrode recovery tank is connected in series with a fourth circulation pump, and the control valve group includes a thirteenth valve and a fourteenth valve. The thirteenth valve is installed on the side of the negative electrode collecting tank close to the battery stack system, and the fourteenth valve is installed between the fourth circulation pump and the negative electrode liquid tank.

[0011] Furthermore, a first liquid level sensor is provided in the positive electrode collection tank; and a second liquid level sensor is provided in the negative electrode collection tank.

[0012] Furthermore, the battery stack system is equipped with a control center, which can control the opening and closing of all valves through instructions, and can also receive liquid level signals from the first liquid level sensor and the second liquid level sensor. The control center can control the first circulation pump and the second circulation pump through instructions, and the control center can also exchange instructions with the main system.

[0013] Furthermore, the heights of the positive electrode collection tank and the negative electrode collection tank are lower than the height of the liquid return port of the battery stack system.

[0014] Furthermore, the capacity of the positive electrode collection tank and the negative electrode collection tank is greater than the capacity of the battery stack system.

[0015] Furthermore, the fuel cell stack system is all the fuel cells required for the operation of the system.

[0016] Furthermore, the sizes of the positive electrode circulation pipeline and the negative electrode circulation pipeline are variable.

[0017] III) Beneficial effects: Compared with the prior art, the device for recovering residual electrolyte of vanadium liquid flow battery stack has the following beneficial effects: 1. The present invention controls the operation of valves and circulation pumps by setting a control center and receiving signals from liquid level sensors, thereby recovering the residual liquid in the battery stack system, thereby reducing the amount of residual liquid in the battery stack system after the system is running, so as to reduce self-discharge heating, delay the attenuation of battery stack service life, and reduce battery capacity loss; 2. The present invention can determine the liquid capacity in the positive and negative collecting tanks by setting the first liquid level sensor and the second liquid level sensor, and then determine the overall working condition of the device and control the work of related structures. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a schematic diagram of the internal structure of the recovery tank of the present invention connected in parallel to the recovery system; Figure 2 The recovery tank of the present invention is connected in parallel to the internal control logic of the recovery system; Figure 3 This is a schematic diagram of the external structure of the recovery tank of the present invention connected in parallel to the recovery system; Figure 4 The recovery tank of the present invention is connected in parallel to the external control logic of the recovery system.

[0019] In the figure: 1. Battery stack system; 2. Positive electrode recovery system; 21. Positive electrode liquid tank; 22. Positive electrode circulation pipeline; 221. Positive electrode liquid inlet pipe; 222. Positive electrode liquid outlet pipe; 223. First valve; 224. Second valve; 23. First circulation pump; 24. Positive electrode collection tank; 241. First liquid level sensor; 25. Positive electrode secondary circulation pipeline; 251. First connecting pipe; 252. Second connecting pipe; 253. Fifth valve; 254. Sixth valve; 255. Third connecting pipe; 256. Seventh valve; 257. Eleventh valve; 258. Twelfth valve; 26. The third circulation pump; 3. Negative electrode recovery system; 31. Negative electrode liquid tank; 32. Negative electrode circulation pipeline; 321. Negative electrode liquid inlet pipe; 322. Negative electrode liquid outlet pipe; 323. Third valve; 324. Fourth valve; 33. Second circulation pump; 34. Negative electrode collection tank; 341. Second liquid level sensor; 35. Negative electrode auxiliary circulation pipeline; 351. Fourth connecting pipe; 352. Fifth connecting pipe; 353. Eighth valve; 354. Ninth valve; 355. Sixth connecting pipe; 356. Tenth valve; 357. Thirteenth valve; 358. Fourteenth valve; 36. Fourth circulation pump. DETAILED DESCRIPTION

[0020] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0021] like Figure 1-4 As shown, the present invention provides a technical solution: a device for recovering residual electrolyte of a vanadium liquid flow battery stack, comprising a stack group system 1, a positive electrode recovery system 2 and a negative electrode recovery system 3.

[0022] Reference Figure 1 The battery stack system 1 is fixed at a corresponding position on the ground, and the battery stack system is provided with a positive electrode liquid outlet, a positive electrode liquid inlet, a negative electrode liquid outlet and a negative electrode liquid inlet.

[0023] Reference Figure 1 , the fuel cell group system 1 refers to all fuel cells operated by the system.

[0024] Reference Figure 1 A positive electrode recovery system 2 is provided between the positive electrode liquid outlet and the positive electrode liquid inlet, and a negative electrode recovery system 3 is provided between the negative electrode liquid outlet and the negative electrode liquid inlet.

[0025] Reference Figure 1 The cathode recovery system 2 includes a cathode liquid tank 21 , and a first liquid inlet is provided on the top of the cathode liquid tank 21 , and a first liquid outlet and a through hole are provided on the bottom.

[0026] Reference Figure 1 The positive electrode recovery system 2 also includes a positive electrode circulation pipeline 22, wherein the positive electrode circulation pipeline 22 includes a positive electrode liquid inlet pipe 221 and a positive electrode liquid outlet pipe 222, the positive electrode liquid inlet pipe 221, the positive electrode liquid tank 21 and the positive electrode liquid outlet pipe 222 are arranged in sequence along the direction of the main circulation, and the two ends of the positive electrode liquid inlet pipe 221 are respectively arranged at the positive electrode liquid outlet of the battery stack system 1 and the first liquid inlet of the positive electrode liquid tank 21, and the positive electrode liquid inlet pipe 221 is fixedly connected to the battery stack system 1 and the positive electrode liquid tank 21; the two ends of the positive electrode liquid outlet pipe 222 are respectively arranged at the first liquid outlet of the positive electrode liquid tank 21 and the positive electrode liquid inlet of the battery stack system 1, and the positive electrode liquid outlet pipe 222 is fixedly connected to the battery stack system 1 and the positive electrode liquid tank 21.

[0027] In this embodiment, the first liquid inlet of the cathode liquid tank 21 is higher than the liquid height in the cathode liquid tank 21 .

[0028] Reference Figure 1 The positive electrode recovery system 2 also includes a first circulation pump 23, which is installed on the positive electrode liquid outlet pipe 222. The first circulation pump 23 is used to pressurize and drive the positive electrode liquid outlet pipe 222, and enable the positive electrode liquid to flow along the main circulation direction.

[0029] Reference Figure 1 The positive electrode liquid outlet pipe 222 is provided with a first valve 223 and a second valve 224 at the liquid inlet end and the liquid outlet end of the first circulation pump 23 , respectively, and the first valve 223 and the second valve 224 are both connected to the positive electrode liquid outlet pipe 222 .

[0030] Reference Figure 1 The negative electrode recovery system 3 includes a negative electrode liquid tank 31, and a second liquid inlet is provided on the upper side of the negative electrode liquid tank 31, and a second liquid outlet and a through groove are provided on the lower side.

[0031] Referring to the figure, the negative electrode recovery system 3 also includes a negative electrode circulation pipeline 32, wherein the negative electrode circulation pipeline 32 includes a negative electrode liquid inlet pipe 321 and a negative electrode liquid outlet pipe 322, the negative electrode liquid inlet pipe 321, the negative electrode liquid tank 31 and the negative electrode liquid outlet pipe 322 are arranged in sequence along the direction of the main circulation, and the two ends of the negative electrode liquid inlet pipe 321 are respectively passed through the negative electrode liquid outlet of the battery stack system 1 and the second liquid inlet of the negative electrode liquid tank 31, and the negative electrode liquid inlet pipe 321 is fixedly connected to the battery stack system 1 and the negative electrode liquid tank 31; the two ends of the negative electrode liquid outlet pipe 322 are respectively passed through the second liquid outlet of the negative electrode liquid tank 31 and the negative electrode liquid inlet of the battery stack system 1, and the negative electrode liquid outlet pipe 322 is fixedly connected to the battery stack system 1 and the negative electrode liquid tank 31.

[0032] In this embodiment, the second liquid inlet of the negative electrode liquid tank 31 is higher than the liquid height in the negative electrode liquid tank 31 .

[0033] Reference Figure 1 The negative electrode circulation pipeline 32 also includes a second circulation pump 33, which is installed on the negative electrode liquid outlet pipe 322. The second circulation pump 33 is used to pressurize and drive the negative electrode liquid outlet pipe 322, and enable the negative electrode liquid to flow along the main circulation direction.

[0034] Reference Figure 1 The negative electrode liquid outlet pipe 322 is provided with a third valve 323 and a fourth valve 324 at the liquid inlet end and the liquid outlet end of the second circulation pump 33 , respectively, and the third valve 323 and the fourth valve 324 are both connected to the negative electrode liquid outlet pipe 322 .

[0035] Reference Figure 1 The positive electrode recovery system 2 further includes a positive electrode collection tank 24 , which is provided with a first liquid inlet and a first liquid outlet, wherein the positive electrode collection tank 24 is equipped with a first liquid level sensor 241 .

[0036] Reference Figure 1 The negative electrode recovery system 3 further includes a negative electrode collection tank 34 , which is provided with a second liquid inlet and a second liquid outlet, wherein the negative electrode collection tank 34 is equipped with a second liquid level sensor 341 .

[0037] Reference Figure 1 In this embodiment, the positive electrode collection tank 24 and the negative electrode collection tank 34 have different shapes, and the heights of the first liquid inlet and the second liquid inlet are higher than the first liquid outlet and the second liquid outlet.

[0038] Reference Figure 1 The volume of the positive electrode collection tank 24 and the negative electrode collection tank 34 is greater than the residual electrolyte volume of the battery stack system 1.

[0039] Embodiment 1:

[0040] Reference Figure 1The positive electrode recovery system 2 also includes a positive electrode auxiliary circulation pipeline 25, which includes a first connecting pipe 251 arranged at the first liquid inlet hole and a second connecting pipe 252 arranged at the first liquid outlet hole, wherein the end of the first connecting pipe 251 away from the positive electrode collection tank 24 is connected to the positive electrode inlet pipe 221, and the end of the second connecting pipe 252 away from the positive electrode collection tank 24 is located between the first valve 223 and the first circulation pump 23, and the second connecting pipe 252 is connected to the positive electrode outlet pipe 222.

[0041] Reference Figure 1 A fifth valve 253 is provided at the first connecting pipe 251 , and a sixth valve 254 is provided at the second connecting pipe 252 .

[0042] Reference Figure 1 The positive electrode secondary circulation pipeline 25 also includes a third connecting pipe 255, one end of the third connecting pipe 255 is penetrated through the through hole, and the other end is connected to the positive electrode liquid outlet pipe 222, and the connection point is located between the second connecting pipe 252 and the second valve 224.

[0043] Reference Figure 1 A seventh valve 256 is provided at the third connecting pipe 255 .

[0044] Reference Figure 1 The negative electrode recovery system 3 also includes a negative electrode auxiliary circulation pipeline 35, which includes a fourth connecting pipe 351 arranged at the second liquid inlet hole and a fifth connecting pipe 352 arranged at the second liquid outlet hole, wherein the end of the fourth connecting pipe 351 away from the negative electrode collection tank 34 is connected to the negative electrode inlet pipe 321, the end of the fifth connecting pipe 352 away from the negative electrode collection tank 34 is located between the third valve 323 and the second circulation pump 33, and the fifth connecting pipe 352 is connected to the negative electrode outlet pipe 322.

[0045] Reference Figure 1 An eighth valve 353 is provided at the fourth connecting pipe 351 , and a ninth valve 354 is provided at the fifth connecting pipe 352 .

[0046] Reference Figure 1 The negative electrode secondary circulation pipeline 35 also includes a sixth connecting pipe 355 , one end of which is passed through the through groove, and the other end is connected to the negative electrode liquid outlet pipe 322 , and the connection point is located between the fifth connecting pipe 352 and the sixth valve 254 .

[0047] Referring to the figure, a tenth valve 356 is provided at the sixth connecting pipe 355 .

[0048] The implementation principle of this embodiment 1 is: Figure 2As shown, when the battery stack system 1 stops running, the control center issues corresponding instructions to close the first valve 223 to the fourth valve 324 and open the fifth valve 253 to the tenth valve 356. At this time, the electrolyte in the positive and negative electrode chambers of the battery stack system 1 flows back to the positive electrode collection tank 24 and the negative electrode collection tank 34. At the same time, the first liquid level sensor 241 and the second liquid level sensor 341 in the positive electrode collection tank 24 and the negative electrode collection tank 34 can determine the volume of the electrolyte and feed back the relevant electrical signals to the control center. Subsequently, the control center feeds back the relevant electrical signals to the first circulation pump 23 and the second circulation pump 33. At the same time, the first circulation pump 23 and the second circulation pump 33 work. , so that the positive electrode electrolyte in the positive electrode collection tank 24 returns to the positive electrode liquid tank 21 through the third connecting pipe 255, and the negative electrode electrolyte in the negative electrode collection tank 34 returns to the negative electrode liquid tank 31 through the sixth connecting pipe 355. When the first liquid level sensor 241 and the second liquid level sensor 341 transmit signals to the control center again, at this time, the electrolyte in the positive electrode collection tank 24 and the negative electrode collection tank 34 is cleaned up, and then the control center issues an instruction to stop the first circulation pump 23 and the second circulation pump 33, and the first valve 223 to the fourth valve 324 are opened, and at the same time the fifth valve 253 to the tenth valve 356 are closed, so that the positive circulation pipeline 22 and the negative circulation pipeline 32 are opened.

[0049] Embodiment 2:

[0050] This embodiment 2 can be used as an alternative to embodiment 1.

[0051] Reference Figure 3 One end of the first connecting pipe 251 is passed through the stack system 1, and the other end is passed through the first liquid inlet hole, and the first connecting pipe 251 is fixedly connected to the stack system 1 and the positive electrode collecting tank 24. The first connecting pipe 251 is installed with an eleventh valve 257.

[0052] Reference Figure 3 One end of the second connecting pipe 252 is passed through the first liquid outlet, and the other end is passed through the through hole, and the second connecting pipe 252 is fixedly connected to the positive electrode collection tank 24 and the positive electrode liquid tank 21. A twelfth valve 258 is installed at the second connecting pipe 252.

[0053] Reference Figure 3 The second connecting pipe 252 is provided with a third circulation pump 26 between the twelfth valve 258 and the positive electrode collecting tank 24 .

[0054] Reference Figure 3 One end of the fourth connecting pipe 351 is passed through the stack system 1, and the other end is passed through the second liquid inlet hole, and the fourth connecting pipe 351 is fixedly connected to the stack system 1 and the negative electrode collecting tank 34. A thirteenth valve 357 is installed at the fourth connecting pipe 351.

[0055] Reference Figure 3 One end of the fifth connecting pipe 352 is passed through the second liquid outlet hole, and the other end is passed through the through groove, and the fifth connecting pipe 352 is fixedly connected to the negative electrode collection tank 34 and the negative electrode liquid tank 31. A fourteenth valve 358 is installed at the fifth connecting pipe 352.

[0056] Reference Figure 3 The fifth connecting pipe 352 is provided with a fourth circulation pump 36 between the fourteenth valve 358 and the negative electrode collecting tank 34 .

[0057] The implementation principle of Example 2 is: Figure 4 As shown, when the battery stack system 1 stops working, the control center controls the first circulation pump 23 and the second circulation pump 33 to stop working, and at the same time the first valve 223 and the third valve 323 are closed, and the eleventh valve 257 to the fourteenth valve 358 are opened. At this time, the electrolyte flows back to the positive electrode collection tank 24 and the negative electrode collection tank 34. When the first liquid level sensor 241 and the second liquid level sensor 341 sense the electrolyte, the relevant electrical signal is transmitted to the control center, and then the control center controls the third circulation pump 26 and the fourth circulation pump 36 to work, and the electrolyte in the positive electrode collection tank 24 and the negative electrode collection tank 34 is filled with electrolyte. The electrolyte is transferred to the positive electrode liquid tank 21 and the negative electrode liquid tank 31 through the second connecting pipe 252 and the fourth connecting pipe 351. When the first liquid level sensor and the second liquid level sensor 341 sense the corresponding liquid level again, and transmit the electrical signal to the control center, the control center then transmits the electrical signal to the third circulation pump 26 and the fourth circulation pump 36, so that the third circulation pump 26 and the fourth circulation pump 36 stop working, the eleventh valve 257 to the fourteenth valve 358 are closed, and the first valve 223 and the third valve 323 are opened at the same time, so that the positive circulation pipeline 22 and the negative circulation pipeline 32 are opened.

Claims

1. A device for recovering residual electrolyte of a vanadium flow battery stack, comprising a stack system (1), characterized in that: The battery stack system (1) is provided with a positive electrode recovery system (2) and a negative electrode recovery system (3) in parallel; The positive electrode recovery system (2) comprises: A positive electrode circulation pipeline (22), the positive electrode circulation pipeline (22) being in communication with the battery stack system (1), the positive electrode circulation pipeline (22) being connected in series with a positive electrode liquid tank (21) and a first circulation pump (23), and the liquid outlet of the first circulation pump (23) being connected to the liquid inlet of the battery stack system (1); A positive electrode collection tank (24), the positive electrode collection tank (24) can be connected in parallel to the inside or outside of the positive electrode circulation pipeline (22), and the positive electrode collection tank (24) and the positive electrode circulation pipeline (22) are in communication; The negative electrode recovery system (3) comprises: A negative electrode circulation pipeline (32), the negative electrode circulation pipeline (32) being in communication with the battery stack system (1), the negative electrode circulation pipeline (32) being connected in series with a negative electrode liquid tank (31) and a second circulation pump (33), and the liquid outlet of the second circulation pump (33) being connected to the liquid inlet of the battery stack system (1); A negative electrode collection tank (34), the negative electrode collection tank (34) can be connected in parallel to the inside or outside of the negative electrode circulation pipeline (32), and the negative electrode collection tank (34) and the negative electrode circulation pipeline (32) are in communication; The positive electrode circulation pipeline (22) and the negative electrode circulation pipeline (32) are provided with a control valve group, and the control valve group is used to control the connection between the positive electrode recovery system (2) and the negative electrode recovery system (3) and the stack system (1).

2. The device for recovering residual electrolyte of a vanadium flow battery stack according to claim 1, characterized in that: When the positive electrode collection tank (24) is connected in parallel to the positive electrode circulation pipeline (22), the positive electrode collection tank (24) is provided with a third connecting pipe (255), one end of the third connecting pipe (255) is connected to the positive electrode liquid tank (21), and the other end is connected to the connecting pipeline between the first circulation pump (23) and the battery stack system (1); When the negative electrode collection tank (34) is connected in parallel to the negative electrode circulation pipeline (32), the negative electrode collection tank (34) is provided with a sixth connecting pipe (355), one end of which is connected to the negative electrode liquid tank (31), and the other end of which is connected to the connecting pipeline between the second circulation pump (33) and the battery stack system (1).

3. The device for recovering residual electrolyte of a vanadium flow battery stack according to claim 2, characterized in that: When the positive electrode collection tank (24) is connected in parallel to the positive electrode circulation pipeline (22), the control valve group comprises a first valve (223), a second valve (224) and a seventh valve (256), and the first valve (223) and the second valve (224) are respectively located at a side of the liquid inlet end and the liquid outlet end of the first circulation pump (23) away from the third connecting pipe (255); The seventh valve (256) is installed on the third connecting pipe (255); When the negative electrode collection tank (34) is connected in parallel to the negative electrode circulation pipeline (32), the control valve group comprises a third valve (323), a fourth valve (324) and a tenth valve (356), and the third valve (323) and the fourth valve (324) are respectively located at a side of the liquid inlet end and the liquid outlet end of the second circulation pump (33) away from the sixth connecting pipe (355); The tenth valve (356) is installed on the sixth connecting pipe (355).

4. The device for recovering residual electrolyte of a vanadium flow battery stack according to claim 3, characterized in that: When the positive electrode collection tank (24) is connected in parallel to the positive electrode circulation pipeline (22), the positive electrode collection tank (24) and the positive electrode liquid tank (21) are connected, the positive electrode recovery tank is connected in series with a third circulation pump (26), and the control valve group includes an eleventh valve (257) and a twelfth valve (258), the eleventh valve (257) is installed on a side of the positive electrode collection tank (24) close to the battery stack system (1), and the twelfth valve (258) is installed between the third circulation pump (26) and the positive electrode liquid tank (21); When the negative electrode collection tank (34) is connected in parallel to the negative electrode circulation pipeline (32), the negative electrode collection tank (34) and the negative electrode liquid tank (31) are connected, and the negative electrode recovery tank is connected in series with a fourth circulation pump (36). The control valve group includes a thirteenth valve (357) and a fourteenth valve (358). The thirteenth valve (357) is installed on a side of the negative electrode collection tank (34) close to the battery stack system (1), and the fourteenth valve (358) is installed between the fourth circulation pump (36) and the negative electrode liquid tank (31).

5. The device for recovering residual electrolyte of a vanadium flow battery stack according to claim 4, characterized in that: A first liquid level sensor (241) is provided in the positive electrode collection tank (24); and a second liquid level sensor (341) is provided in the negative electrode collection tank (34).

6. The device for recovering residual electrolyte of a vanadium flow battery stack according to claim 5, characterized in that: The battery stack system (1) is equipped with a control center, which can control the opening and closing of all valves through instructions, and can also receive liquid level signals from the first liquid level sensor (241) and the second liquid level sensor (341). The control center can control the first circulation pump (23) and the second circulation pump (33) through instructions, and the control center can also exchange instructions with the main system.

7. The device for recovering residual electrolyte of a vanadium flow battery stack according to claim 1, characterized in that: The heights of the positive electrode collection tank (24) and the negative electrode collection tank (34) are lower than the height of the liquid return port of the battery stack system (1).

8. The device for recovering residual electrolyte of a vanadium flow battery stack according to claim 1, characterized in that: The capacity of the positive electrode collection tank (24) and the negative electrode collection tank (34) is greater than the capacity of the battery stack system (1).

9. The device for recovering residual electrolyte of a vanadium flow battery stack according to claim 1, characterized in that: The battery stack system (1) is the entire battery stack required for system operation.

10. The device for recovering residual electrolyte of a vanadium flow battery stack according to claim 1, characterized in that: The sizes of the positive electrode circulation pipeline (22) and the negative electrode circulation pipeline (32) are variable.

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