Method for removing V2O5 precipitate in all-vanadium redox flow battery and battery system

Abstract

The invention relates to a method for removing V2O5 precipitates in an all-vanadium redox flow battery and a battery system. The method comprises the following steps: S1, introducing reducing ions into a positive electrode through an introduction device, and enabling the reducing ions to react with V2O5 precipitates of the positive electrode so as to remove the V2O5 precipitates of the positive electrode. According to the scheme provided by the invention, the V2O5 precipitate in the vanadium liquid battery can be effectively removed under the condition that the original battery is not disassembled.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of batteries, in particular to a method for removing V2O5 precipitate in a full vanadium redox flow battery and a battery system. BACKGROUND

[0002] In recent years, in order to meet the increasing material needs of the people, the global per capita energy consumption continues to increase, which further aggravates the greenhouse effect and global warming. In order to solve the energy consumption and global climate change, governments around the world have proposed the requirement of reducing carbon emissions. In order to achieve the goal of reducing carbon emissions, significantly increasing the proportion of clean and renewable energy such as wind power and solar power in the total power consumption is the only way to build a new energy system. However, the renewable energy generation such as wind power and solar power is very unstable, and it is urgent to develop safe, efficient, zero active, and widely applicable large-scale energy storage technology. The full vanadium redox flow battery (the positive active material contains VO 2+ / VO2 + ) such as the full vanadium redox flow battery is highly consistent with the demand for large-scale energy storage due to its intrinsic safety and energy and power decoupling, expansion flexibility, and has shown great application prospects in large-scale energy storage systems. However, the full vanadium redox flow battery has poor high-temperature stability, and when operating above 40℃, the positive electrolyte will precipitate to form insoluble V2O5 precipitate. The precipitate gradually accumulates and adheres to the pipeline and the inside of the battery, which hinders the flow of the electrolyte and causes rapid capacity decay of the battery, and even damage to the battery system.

[0003] In the related art, the high-temperature stability of the positive electrolyte is improved by adding electrolyte additives, but the generation of V2O5 cannot be avoided when operating above 40℃ for a long time. Even by disassembling the battery to remove V2O5, this process is time-consuming, laborious and expensive, and may also damage the performance and components of the battery. SUMMARY

[0004] To solve or partially solve the problems in the related art, the present application provides a method for removing V2O5 precipitate in a full vanadium redox flow battery and a battery system, which can effectively remove V2O5 precipitate in a vanadium liquid battery without disassembling the original battery.

[0005] The first aspect of the present application provides a method for removing V2O5 precipitate in a full vanadium redox flow battery, comprising: S1, introducing reducing ions into the positive electrode by the introduction device, so that the reducing ions react with the V2O5 precipitate of the positive electrode to remove the V2O5 precipitate of the positive electrode.

[0006] As an optional embodiment, the S1 comprises: S10, driving at least part of the negative electrolyte in the negative electrolyte tank to flow into the positive electrolyte tank by the driving device 3, so that the reducing ions in the negative electrolyte enter the positive electrolyte tank, and the reducing ions react with the V2O5 precipitate in the positive electrolyte tank to generate the first composite electrolyte; or S20, controlling the positive electrode to generate reducing ions by the reaction control device, so that the reducing ions react with the V2O5 precipitate in the positive electrolyte tank to generate the second composite electrolyte.

[0007] As an optional embodiment, after S10, it further includes: S11, driving the first composite electrolyte in the positive electrolyte tank to flow into the positive electrode side by the positive driving pump to remove the V2O5 precipitate in the positive electrode side; S12, driving the remaining negative electrolyte in the negative electrolyte tank to flow into the positive electrolyte tank, and mixing all the electrolytes in the positive electrolyte tank to obtain the first mixed electrolyte; S13, driving the first mixed electrolyte in the positive electrolyte tank to be distributed into the negative electrolyte tank.

[0008] As an optional embodiment, in S10, the electrolyte is driven to flow by the mixing pump or the negative driving pump.

[0009] As an optional embodiment, in S12, the electrolyte is driven to flow by the mixing pump or the negative driving pump.

[0010] As an optional embodiment, in S13, the electrolyte is driven to flow by the mixing pump or the positive driving pump.

[0011] As an optional embodiment, S20 includes: S200, reversing the polarity of the positive electrode and the negative electrode by the reverse connection device, so that the positive electrode generates reducing ions by reduction reaction.

[0012] As an optional embodiment, S200 includes: reversing the circuit of the positive electrode and the negative electrode by the reverse connection device.

[0013] As an optional embodiment, after S200, it further includes: Monitoring the dissolution state of the V2O5 precipitate in the positive electrode; according to the performance parameters of the electrolyte, and combining the dissolution state of the V2O5 precipitate in the positive electrode, the circuit reverse connection duration is controlled.

[0014] As an optional embodiment, the reducing ions include at least one ion of V 2+ , V 3+ .

[0015] The second aspect of the embodiment of the present application provides a full vanadium redox flow battery system, comprising: The full vanadium redox flow battery comprises a positive electrode, a negative electrode and a separator, the positive electrode comprises a positive electrode liquid storage tank, a positive electrode driving pump and a positive electrode side electrode, the positive electrode driving pump is used for pumping the positive electrode electrolyte in the positive electrode liquid storage tank into the positive electrode side electrode; the negative electrode comprises a negative electrode liquid storage tank, a negative electrode driving pump and a negative electrode side electrode, the negative electrode driving pump is used for pumping the negative electrode electrolyte in the negative electrode liquid storage tank into the negative electrode side electrode; The introduction device is connected with the positive electrode and the negative electrode, and is used for introducing the reducing ions into the positive electrode, so that the reducing ions react with the V2O5 precipitate of the positive electrode to remove the V2O5 precipitate of the positive electrode.

[0016] As an optional embodiment, the introduction device comprises a driving device, the driving device is used for driving the negative electrode electrolyte in the negative electrode liquid storage tank to flow into the positive electrode liquid storage tank, so that the reducing ions in the negative electrode electrolyte enter the positive electrode liquid storage tank, and the reducing ions react with the V2O5 precipitate in the positive electrode liquid storage tank to generate a first composite electrolyte; or the introduction device comprises a reaction control device, the reaction control device is used for controlling the positive electrode to generate the reducing ions, so that the reducing ions react with the V2O5 precipitate in the positive electrode liquid storage tank to generate a second composite electrolyte.

[0017] As an optional embodiment, the driving device comprises a mixing pump and a first connecting pipe, the first connecting pipe is in communication with the positive electrode liquid storage tank and the negative electrode liquid storage tank, and the mixing pump is arranged on the first connecting pipe and is used for driving the negative electrode electrolyte in the negative electrode liquid storage tank to flow into the positive electrode liquid storage tank.

[0018] As an optional embodiment, the driving device comprises a first connecting pipe, the first connecting pipe connects the positive electrode driving pump and the negative electrode driving pump, and the negative electrode driving pump is further used for driving the negative electrode electrolyte in the negative electrode liquid storage tank to flow into the positive electrode liquid storage tank.

[0019] As an optional embodiment, the reaction control device comprises a reverse connection device, the reverse connection device is used for controlling the circuit of the positive electrode and the negative electrode to be reversely connected.

[0020] The technical scheme provided by the present application can include the following beneficial results: The present application can achieve the purpose of removing V2O5 in the battery system without disassembling the full vanadium redox flow battery or the electric pile and introducing new chemical elements, thereby avoiding the waste of manpower and material resources caused by disassembly in the traditional method and the damage to the performance and parts of the battery. The capacity of the full vanadium redox flow battery can be completely restored to the level before the precipitation occurs after mixing the liquid by the method, the method has low cost, simple operation, short time consumption, good effect and high flexibility, and has great application prospect.

[0021] The technical solution of the present application can also quickly restore the vanadium redox flow battery system in which V2O5 precipitation occurs to the performance before the precipitation occurs, greatly reducing the operation and maintenance cost, and can be widely used in the field of vanadium redox flow batteries.

[0022] It should be understood that the foregoing general description and the following detailed description are only exemplary and explanatory, and are not limiting to the present application. BRIEF DESCRIPTION OF DRAWINGS

[0023] The above and other objects, features and advantages of the present application will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings, in which like reference characters refer to like parts throughout the several views, and in which the exemplary embodiments of the present application are shown.

[0024] Figure 1 is a structural schematic diagram of a vanadium redox flow battery system shown in an embodiment of the present application; Figure 2 is another structural schematic diagram of a vanadium redox flow battery system shown in an embodiment of the present application; Figure 3 is a reaction schematic diagram generated after the positive and negative polarities are reversed in a vanadium redox flow battery system shown in an embodiment of the present application; Fig. 4(a) is a schematic diagram of V2O5 precipitation generated in a positive electrode liquid storage tank shown in Embodiment 1 of the present application; Fig. 4(b) is a schematic diagram of V2O5 precipitation generated in a positive electrode side electrode and flow channel shown in Embodiment 1 of the present application; Fig. 5(a) is a state diagram of a positive electrode liquid storage tank and a negative electrode liquid storage tank of a vanadium redox flow battery after precipitation occurs shown in Embodiment 1 of the present application; Fig. 5(b) is a state diagram of introducing negative electrode electrolyte into the positive electrode liquid storage tank to eliminate V2O5 precipitation in the positive electrode liquid storage tank shown in Embodiment 1 of the present application; Fig. 5(c) is a state diagram of the positive electrode liquid storage tank and the negative electrode liquid storage tank after V2O5 precipitation in a vanadium redox flow battery system is completely removed and mixed liquid is redistributed shown in Embodiment 1 of the present application; Fig. 6(a) is a discharge capacity test comparison diagram before and after precipitation of a vanadium redox flow battery shown in Embodiment 1 of the present application; Fig. 6(b) is a voltage efficiency test comparison diagram before and after precipitation of a vanadium redox flow battery shown in Embodiment 1 of the present application; Fig. 6(c) is a discharge capacity test comparison diagram before precipitation and after V2O5 precipitation is removed and mixed liquid of a vanadium redox flow battery shown in Embodiment 1 of the present application; Fig. 6(d) is a voltage efficiency test comparison diagram before precipitation and after V2O5 precipitation is removed and mixed liquid of a vanadium redox flow battery shown in Embodiment 1 of the present application; Figure 7(a) is a comparison chart of discharge capacity test of the all-vanadium redox flow battery before precipitation and after polarity reversal according to an embodiment of the present application; Figure 7(b) is a comparison chart of voltage efficiency test of the all-vanadium redox flow battery before precipitation and after polarity reversal according to an embodiment of the present application.

[0025] In the drawings: 10, positive electrolyte tank; 11, positive electrolyte pump; 12, positive electrode; 20, negative electrolyte tank; 21, negative electrolyte pump; 22, negative electrode; 3, driving device; 30, mixing pump; 31, first connecting pipe; 32, second connecting pipe. DETAILED DESCRIPTION

[0026] Embodiments of the present application will be described in more detail with reference to the drawings. Although the embodiments of the present application are shown in the drawings, it should be understood that the present application can be implemented in various forms and should not be limited by the embodiments set forth herein. Rather, these embodiments are provided so that the present application will be thorough and complete, and will fully convey the scope of the present application to those skilled in the art.

[0027] The terminology used in the present application is for the purpose of describing particular embodiments only and is not intended to be limiting of the present application. As used in the present application and the appended claims, the singular forms "a," "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "and / or," as used herein, refers to and encompasses any and all possible combinations of one or more of the associated listed items.

[0028] It will be understood that, although the terms "first," "second," "third," etc. can be used herein to describe various information, these terms are not intended to denote a particular order or hierarchy. These terms are used only to distinguish one from another. For example, a first information can also be referred to as a second information, and similarly, a second information can also be referred to as a first information, without departing from the scope of the present application. As such, features defined with "first," "second" can explicitly or implicitly include one or more of the features. In the description of the present application, the meaning of "a plurality of" is two or more, unless otherwise specifically defined.

[0029] In the related art, the high-temperature stability of the positive electrolyte is improved by adding electrolyte additives, but the generation of V2O5 cannot be avoided when running for a long time at a temperature above 40°C; even by disassembling the battery to remove V2O5, but this process is time-consuming, laborious and expensive, and may also damage the performance and components of the battery.

[0030] To solve the above problems, the embodiment of the present application provides a method for removing V2O5 precipitate in a full vanadium redox flow battery, which can effectively remove the V2O5 precipitate in the vanadium liquid battery without disassembling the original battery.

[0031] The technical solutions of the embodiments of the present application are described in detail below with reference to the drawings.

[0032] Referring to Figure 1 and Figure 2 , the embodiment of the present application provides a method for removing V2O5 precipitate in a full vanadium redox flow battery, which includes: S1, introducing reducing ions into the positive electrode through the introduction device, so that the reducing ions react with the V2O5 precipitate of the positive electrode to remove the V2O5 precipitate of the positive electrode.

[0033] The full vanadium redox flow battery system in the embodiment of the present application can include a full vanadium redox flow battery, which includes a positive electrode, a negative electrode and a separator, the positive electrode includes a positive electrode liquid storage tank 10, a positive electrode driving pump 11 and a positive electrode side electrode 12, the positive electrode driving pump 11 is used to pump the positive electrode electrolyte in the positive electrode liquid storage tank 10 into the positive electrode side electrode 12; the negative electrode includes a negative electrode liquid storage tank 20, a negative electrode driving pump 21 and a negative electrode side electrode 22, the negative electrode driving pump 21 is used to pump the negative electrode electrolyte in the negative electrode liquid storage tank 20 into the negative electrode side electrode 22.

[0034] The full vanadium redox flow battery system in the embodiment of the present application can also include an introduction device, which is connected with the positive electrode and the negative electrode and is used to introduce reducing ions into the positive electrode, so that the reducing ions react with the V2O5 precipitate of the positive electrode to remove the V2O5 precipitate of the positive electrode.

[0035] The introduction device in the embodiment of the present application can include a driving device 3 or a reaction control device, and the reducing ions can be introduced into the positive electrode by the driving device 3 to make the negative electrode electrolyte in the negative electrode liquid storage tank 20 flow into the positive electrode liquid storage tank 10, so that the reducing ions in the negative electrode electrolyte enter the positive electrode liquid storage tank 10; or the reaction control device can be used to control the positive electrode to generate reducing ions by a reduction reaction. The V2O5 precipitate of the positive electrode can be removed without disassembling the battery and introducing new chemicals.

[0036] Therefore, the embodiment of the present application can introduce reducing ions into the positive electrode by adding an introduction device to the original full vanadium redox flow battery, so as to make the reducing ions react with the V2O5 precipitate of the positive electrode to remove the V2O5 precipitate of the positive electrode.

[0037] The embodiment of the present application can introduce reducing ions into the positive electrode in the following two ways, which correspond to the driving device 3 and the reaction control device of the introduction device respectively, and the two ways will be described in detail below.

[0038] The first mode corresponds to the driving device 3 of the introducing device, and includes the following steps: S10. Driving at least part of the negative electrolyte in the negative electrolyte tank 20 to flow into the positive electrolyte tank 10 by the driving device 3, so that the reducing ions in the negative electrolyte enter the positive electrolyte tank 10, and the reducing ions react with the V2O5 precipitate in the positive electrolyte tank 10 to generate a first composite electrolyte.

[0039] In the embodiment of the present application, the negative electrolyte in the negative electrolyte tank 20 can be a negative electrolyte containing V 2+ , V 3+ , or a mixture of the two in any ratio, and can also be a negative electrolyte added with formic acid, oxalic acid, sulfurous acid and a solution thereof.

[0040] When the negative electrolyte in the negative electrolyte tank 20 is a negative electrolyte containing V 2+ , V 3+ , or a mixture of the two in any ratio, the reducing ions in the negative electrolyte include at least one ion of V 2+ , V 3+ .

[0041] When the negative electrolyte in the negative electrolyte tank 20 is a negative electrolyte added with formic acid, oxalic acid, sulfurous acid and a solution thereof, the reducing ions in the negative electrolyte can also include at least one ion of HCOO - , C2O4 2- , SO3 2- .

[0042] The embodiment of the present application drives the negative electrolyte in the negative electrolyte tank 20 to flow into the positive electrolyte tank 10, so that the reducing ions such as V 2+ , V 3+ in the negative electrolyte enter the positive electrolyte tank 10, and the V2O5 precipitate in the positive electrolyte tank 10 is reduced to easily soluble low-valence vanadium ions, so as to remove the V2O5 precipitate in the positive electrolyte tank 10. Referring to Figure 2 , the reducing reaction is as follows:

[0043]

[0044] In the embodiment of the present application, the first composite electrolyte contains the product of the reduction reaction.

[0045] As a preferred embodiment, the negative electrolyte in the negative electrolyte tank 20 is driven to flow into the positive electrolyte tank 10 by a mixing pump or a negative driving pump in S10.

[0046] The embodiment of the present application can also drive the negative electrolyte in the negative electrolyte tank 20 to flow into the positive electrolyte tank 10 through the driving device 3. When the driving device 3 is used to drive the negative electrolyte in the negative electrolyte tank 20 to flow into the positive electrolyte tank 10, referring to Figure 1 , the driving device 3 can include a mixing pump 30 and a first connecting pipe 31, the first connecting pipe 31 is in communication with the positive electrolyte tank 10 and the negative electrolyte tank 20, and the mixing pump 30 is arranged on the first connecting pipe 31 and is used to drive all the negative electrolyte in the negative electrolyte tank 20 to flow into the positive electrolyte tank 10; or, referring to Figure 2 , the driving device 3 can only include a second connecting pipe 31, the second connecting pipe 31 connects the positive driving pump 11 and the negative driving pump 21, and the positive driving pump 11 is also used to drive the negative electrolyte in the negative electrolyte tank 20 to flow into the positive electrolyte tank 10.

[0047] As a preferred embodiment, driving the negative electrolyte in the negative electrolyte tank 20 to flow into the positive electrolyte tank 10 in S10 can include: According to the actual capacity loss of the battery and the performance parameters of the electrolyte, the flow of the negative electrolyte in the negative electrolyte tank 20 flowing into the positive electrolyte tank 10 is adjusted.

[0048] The embodiment of the present application can adjust the flow of the negative electrolyte in the negative electrolyte tank 20 flowing into the positive electrolyte tank 10 by controlling the rotating speed of the mixing pump 30 or the negative driving pump 21.

[0049] As a preferred embodiment, after driving the negative electrolyte in the negative electrolyte tank 20 to flow into the positive electrolyte tank 10, it further includes: S11, driving the first composite electrolyte in the positive electrolyte tank 10 to flow into the positive electrode side 12 through the positive driving pump 11 to remove the V2O5 precipitate in the positive electrode side 12.

[0050] In the embodiment of the present application, the reducing ion can include at least one ion of V 2+ , V 3+ After removing the V2O5 precipitate in the positive electrolyte tank 10, the embodiment of the present application can also drive the first composite electrolyte in the positive electrolyte tank 10 to flow into the positive electrode side 12 through the positive driving pump 11 to reduce the V2O5 precipitate in the positive electrode side 12 to the easily soluble low-valence vanadium ion, so as to remove the V2O5 precipitate in the positive electrode side 12.

[0051] S12, driving the remaining negative electrolyte in the negative electrolyte tank 20 to flow into the positive electrolyte tank 10, and mixing all the electrolyte in the positive electrolyte tank 10 to obtain the first mixed electrolyte.

[0052] In the embodiments of the present application, the electrolyte in the positive electrolyte tank 10 can be mixed by heating, vibration or the like, so that the reduction reaction is more sufficient, and the difference in vanadium ion valence state of the positive and negative electrolytes can be balanced.

[0053] S13, the first mixed electrolyte in the positive electrolyte tank 10 is distributed into the negative electrolyte tank 20.

[0054] In the embodiments of the present application, the method can make the capacity of the all-vanadium redox flow battery completely recover to the level before the precipitation occurs after mixing the liquid, and can quickly restore the performance of the all-vanadium redox flow battery system before the precipitation occurs, thereby greatly reducing the operation and maintenance cost.

[0055] As a preferred embodiment, the remaining negative electrolyte in the negative electrolyte tank 20 is driven to flow into the positive electrolyte tank 10 by the mixing pump 30 or the negative driving pump 21 in S12.

[0056] The embodiments of the present application can also drive the remaining negative electrolyte in the negative electrolyte tank 20 to flow into the positive electrolyte tank 10 by the driving device 3. When the driving device 3 is used to drive the remaining negative electrolyte in the negative electrolyte tank 20 to flow into the positive electrolyte tank 10, referring to Figure 1 , the driving device 3 can include a mixing pump 30 and a first connecting pipe 31, the first connecting pipe 31 communicates with the positive electrolyte tank 10 and the negative electrolyte tank 20, and the mixing pump 30 is arranged on the first connecting pipe 31 and is used to drive the remaining negative electrolyte in the negative electrolyte tank 20 to flow into the positive electrolyte tank 10; or, referring to Figure 2 , the driving device 3 can only include a second connecting pipe 32, the first connecting pipe 32 connects the positive driving pump 11 and the negative driving pump 21, and the positive driving pump 11 is also used to drive the remaining negative electrolyte in the negative electrolyte tank 20 to flow into the positive electrolyte tank 10.

[0057] As a preferred embodiment, the first mixed electrolyte in the positive electrolyte tank 10 is distributed into the negative electrolyte tank 20 by the mixing pump 30 or the positive driving pump 11 in S13.

[0058] The embodiments of the present application can also distribute the first mixed electrolyte in the positive electrolyte tank 10 into the negative electrolyte tank 20 by the driving device 3. When the driving device 3 is used to distribute the mixed electrolyte in the positive electrolyte tank 10 into the negative electrolyte tank 20, referring to Figure 1 , the driving device 3 can include a mixing pump 30 and a first connecting pipe 31, the first connecting pipe 31 communicates with the positive electrolyte tank 10 and the negative electrolyte tank 20, and the mixing pump 30 is arranged on the first connecting pipe 31 and is used to drive the first mixed electrolyte in the positive electrolyte tank 10 to flow into the negative electrolyte tank 20; or, referring to Figure 2The driving device 3 may only include the second connecting pipe 32 , the first connecting pipe 32 connects the positive driving pump 11 and the negative driving pump 21 , and the positive driving pump 11 is also used to drive the first mixed electrolyte in the positive electrode storage tank 10 to flow into the negative electrode storage tank 20 .

[0059] As a preferred embodiment, the step of driving the mixed electrolyte in the positive electrode liquid storage tank 10 to be distributed into the negative electrode liquid storage tank 20 in S13 includes: Based on the actual battery capacity loss and electrolyte performance parameters, at least one of the distribution ratio of the negative electrolyte flowing from the negative electrode storage tank 20 to the positive electrode storage tank 10 and the electrolyte replenishment amount is adjusted to optimize the electrolyte's conductivity, stability, and reactivity, thereby achieving rapid and accurate recovery of battery capacity.

[0060] The second method corresponds to the reaction control device of the introduction device, comprising the following steps: As an optional embodiment, introducing reducing ions into the positive electrode includes: S20, controlling the positive electrode to undergo a reduction reaction by the reaction control device to generate reducing ions, so that the reducing ions and the V2O5 precipitate in the positive electrode storage tank 10 undergo a secondary reduction reaction to generate a second composite electrolyte.

[0061] In the embodiment of the present application, the reaction control device controls the positive electrode to undergo a reduction reaction to generate reducing ions, such as V 2+ 、V 3+ , reducing the V2O5 precipitate in the positive electrode storage tank to easily soluble low-valent vanadium ions to remove the V2O5 precipitate in the positive electrode storage tank 10.

[0062] In the embodiment of the present application, the second composite electrolyte includes a secondary reduction reaction product.

[0063] As a preferred embodiment, controlling the reduction reaction of the positive electrode to generate reducing ions by the reaction control device in S20 includes: S200 , the polarities of the positive electrode and the negative electrode are reversed by the reverse connection device of the reaction control device, so that a reduction reaction occurs at the positive electrode to generate reducing ions.

[0064] In the embodiment of the present application, reversing the polarity of the positive electrode and the negative electrode may refer to changing the positive electrode into the negative electrode and the negative electrode into the positive electrode, so that the positive electrode undergoes a reduction reaction to generate reducing ions.

[0065] As a preferred embodiment, S200 may include reversing the circuits of the positive and negative electrodes by using a reverse connection device.

[0066] The reverse connection device in the embodiments of the present application can be a circuit reverse connection control device (not shown in the figure), and the circuit reverse connection control device is used to apply a reverse voltage (the positive electrode is connected to the negative electrode of the power supply, and the negative electrode is connected to the positive electrode of the power supply) to the battery, so that the positive electrode generates a reduction reaction, and the negative electrode generates an oxidation reaction.

[0067] In the embodiments of the present application, the negative electrode electrolyte in the negative electrode liquid storage tank 20 can be a negative electrode electrolyte including V 2+ , V 3+ or a mixture of the two in any ratio, and can also be a negative electrode electrolyte added with formic acid, oxalic acid, sulfurous acid and a solution thereof. The positive electrode electrolyte in the positive electrode liquid storage tank 10 can be a positive electrode electrolyte including VO 2+ , VO2 + or a mixture of the two in any ratio. The electrochemical reaction occurring in the positive electrode includes:

[0068]

[0069] The electrochemical reaction occurring in the negative electrode includes:

[0070]

[0071] When the circuit of the positive electrode and the negative electrode is reversely connected, referring to Figure 3 , the electrochemical reaction occurring in the positive electrode includes:

[0072]

[0073]

[0074] The electrochemical reaction occurring in the negative electrode includes:

[0075]

[0076] As a preferred embodiment, after the circuit of the positive electrode and the negative electrode is reversely connected by the reverse connection device in S200, the method further includes: monitoring the dissolution state of the V2O5 precipitate in the positive electrode; and controlling the duration of the circuit reverse connection according to the performance parameters of the electrolyte and the dissolution state of the V2O5 precipitate in the positive electrode.

[0077] The embodiments of the present application can start the circuit reverse connection under the condition that the SOC of the battery is not more than 50%.

[0078] The embodiment of the present application can use whether the open circuit voltage of the positive and negative electrolytes is greater than 0.4V after the circuit is reversed as a judgment condition for whether V2O5 is completely dissolved. If the open circuit voltage of the positive and negative electrolytes is greater than 0.4V, it means that V2O5 is completely dissolved. Then, based on the performance parameters of the electrolyte, such as the volume of the positive and negative electrolytes after dissolution, it is judged whether to end the circuit reversal. If the volume of the positive electrolyte exceeds 20% of the negative electrolyte, the circuit reversal is ended; if the volume of the positive electrolyte does not exceed 20% of the negative electrolyte, the circuit reversal is maintained. The embodiment of the present application performs circuit reversal under appropriate conditions and controls the duration of circuit reversal, which can achieve the rebalancing of the positive and negative electrolytes, thereby achieving the purpose of optimizing battery performance.

[0079] As a preferred embodiment, after the circuit reverse connection is ended or the circuit reverse connection is maintained, the method further includes: The positive electrode electrolyte in the positive electrode storage tank 10 and the negative electrode electrolyte in the negative electrode storage tank 20 are mixed and redistributed, and the mixing conditions are determined.

[0080] In the embodiments of the present application, the mixing conditions may refer to the mixing mass ratio / volume ratio of the positive electrode electrolyte and the negative electrode electrolyte, etc.

[0081] In the embodiment of the present application, all the negative electrode electrolyte in the negative electrode storage tank can be driven to flow into the positive electrode storage tank according to the mixing conditions, and all the electrolytes are mixed in the positive electrode storage tank to obtain a second mixed electrolyte; and the second mixed electrolyte in the positive electrode storage tank is then distributed to the negative electrode storage tank.

[0082] In the embodiment of the present application, the electrolyte in the positive electrode liquid storage tank 10 and the negative electrode liquid storage tank 20 can also be mixed by the driving device 3. Figure 1 The driving device 3 may include a mixing pump 30 and a first connecting pipe 31. The first connecting pipe 31 is connected to both the positive electrode liquid storage tank 10 and the negative electrode liquid storage tank 20. The mixing pump 30 is provided on the first connecting pipe 31 and is used to drive the electrolyte in the positive electrode liquid storage tank 10 to flow into the negative electrode liquid storage tank 20. Alternatively, see Figure 2 The driving device 3 may only include a second connecting pipe 32, which connects the positive electrode driving pump 11 and the negative electrode driving pump 21. The positive electrode driving pump 21 is also used to drive the electrolyte in the positive electrode storage tank 10 to flow into the negative electrode storage tank 20 to achieve rebalancing of the positive and negative electrode electrolytes.

[0083] As a preferred embodiment, the reducing ions may include V 2+ 、V 3+ At least one ion in.

[0084] In the embodiment of the present application, the negative electrode electrolyte in the negative electrode storage tank 20 may include V 2+ 、V 3+Or any proportion of the mixture of the negative electrolyte, can also be for the negative electrolyte including formic acid, oxalic acid, sulfurous acid and its solution.

[0085] The embodiment of the present application introduces the reducing ions such as V 2+ , V 3+ Into the positive electrode, so that the reducing ions react with the V2O5 precipitate of the positive electrode, and the V2O5 precipitate of the positive electrode is reduced to the low-valence vanadium ions which are easily soluble, so as to remove the V2O5 precipitate of the positive electrode.

[0086] The embodiment of the present application utilizes the high-valence oxidizing property of the vanadium ions in V2O5 and the reducing property of the vanadium ions on the negative electrode side, and reduces the high-valence and insoluble V2O5 to the low-valence and soluble vanadium ions by introducing the negative electrolyte into the mixed solution of the positive electrode or by reversing the polarity of the positive and negative electrodes, so as to remove the V2O5 in the all-vanadium redox flow battery system. Finally, the electrolyte on the positive and negative electrodes of the all-vanadium redox flow battery after removing the V2O5 is mixed to restore the capacity of the battery.

[0087] The method of the embodiment of the present application is not only suitable for a single all-vanadium redox flow battery, but also suitable for an all-vanadium redox flow battery stack; it is suitable for a flow-by type battery containing flow channels in the bipolar plate, and also suitable for a flow-though type all-vanadium redox flow battery without flow channels in the bipolar plate; further, the method is not only suitable for a commercial all-vanadium redox flow battery, but also suitable for a mixed system of the all-vanadium redox flow battery and other batteries.

[0088] As an optional embodiment, the embodiment of the present application can introduce the reducing ions into the positive electrode under the condition that the battery is not more than 50% SOC.

[0089] Under the condition that the battery is not more than 50% SOC, the concentration of the electrolyte is increased, and the probability of V2O5 precipitate generated in the positive electrode is larger, so that the effect of removing the V2O5 precipitate is better.

[0090] Corresponding to the foregoing application function implementation method embodiment, the present application also provides an all-vanadium redox flow battery system and a corresponding embodiment.

[0091] Referring to Figure 1 and Figure 2 , the embodiment of the present application also provides an all-vanadium redox flow battery system, which comprises: All-vanadium liquid flow battery, the all-vanadium liquid flow battery includes a positive electrode, a negative electrode and a diaphragm. The positive electrode includes a positive electrode storage tank 10, a positive electrode drive pump 11 and a positive electrode side electrode 12. The positive electrode drive pump 11 is used to pump the positive electrode electrolyte in the positive electrode storage tank 10 into the positive electrode side electrode 12; the negative electrode includes a negative electrode storage tank 20, a negative electrode drive pump 21 and a negative electrode side electrode 22. The negative electrode drive pump 21 is used to pump the negative electrode electrolyte in the negative electrode storage tank 20 into the negative electrode side electrode 22.

[0092] The introduction device is connected to the positive electrode and the negative electrode and is used to introduce reducing ions into the positive electrode, so that the reducing ions react with the V2O5 precipitate at the positive electrode to remove the V2O5 precipitate at the positive electrode.

[0093] In the embodiment of the present application, the diaphragm can be one or a combination of any two or more of proton exchange membranes such as Nafion membrane, Celgard porous membrane, PBI, SPEEK, etc.

[0094] In the embodiment of the present application, the introduction device may include a driving device 3 and a reaction control device. The reducing ions are introduced into the positive electrode by driving the negative electrode electrolyte in the negative electrode reservoir 20 to flow into the positive electrode reservoir 10 via the driving device 3, thereby allowing the reducing ions in the negative electrode electrolyte to enter the positive electrode reservoir 10. Alternatively, the reaction control device may be used to control a reduction reaction at the positive electrode to generate the reducing ions. This allows the removal of V2O5 precipitates at the positive electrode without disassembling the battery or introducing new chemical substances.

[0095] Therefore, the embodiment of the present application can achieve the purpose of introducing reducing ions into the positive electrode by only adding an introduction device on the basis of the original all-vanadium redox flow battery, so that the reducing ions react with the V2O5 precipitate at the positive electrode to remove the V2O5 precipitate at the positive electrode.

[0096] As an optional embodiment, the introduction device may include a driving device 3, which is used to drive the negative electrode electrolyte in the negative electrode storage tank 20 to flow into the positive electrode storage tank 10, so that the reducing ions in the negative electrode electrolyte enter the positive electrode storage tank 10, and the reducing ions react with the V2O5 precipitation in the positive electrode storage tank 10 to generate a first composite electrolyte.

[0097] The driving device 3 can also be used to drive the first composite electrolyte in the positive electrode storage tank 10 to flow into the positive electrode side 12 through the positive electrode driving pump 11 to remove the V2O5 precipitation in the positive electrode side 12; drive all the remaining negative electrode electrolyte in the negative electrode storage tank 20 to flow into the positive electrode storage tank 110, and mix all the electrolytes in the positive electrode storage tank 10 to obtain a first mixed electrolyte; drive the first mixed electrolyte in the positive electrode storage tank 10 to be distributed into the negative electrode storage tank 20.

[0098] As a preferred embodiment, seeFigure 1 The driving device 3 comprises a mixing pump 30 and a first connecting pipe 31, the first connecting pipe 31 is communicated with the positive electrolyte tank 10 and the negative electrolyte tank 20, the mixing pump 30 is arranged on the first connecting pipe 31 and is used to drive the negative electrolyte in the negative electrolyte tank 20 to flow into the positive electrolyte tank 10; or, referring to Figure 2 The driving device 3 comprises a first connecting pipe 32, the first connecting pipe 32 connects the positive driving pump 11 and the negative driving pump 21, and the negative driving pump 21 is further used to drive the negative electrolyte in the negative electrolyte tank 20 to flow into the positive electrolyte tank 10.

[0099] The driving device 3 can drive the negative electrolyte in the negative electrolyte tank 20 to flow into the positive electrolyte tank 10. When the driving device 3 is used to drive the negative electrolyte in the negative electrolyte tank 20 to flow into the positive electrolyte tank 10, the driving device 3 can comprise a mixing pump 30 and a first connecting pipe 31, the first connecting pipe 31 is communicated with the positive electrolyte tank 10 and the negative electrolyte tank 20, the mixing pump 30 is arranged on the first connecting pipe 31 and is used to drive all the negative electrolyte in the negative electrolyte tank 20 to flow into the positive electrolyte tank 10; or, the driving device 3 can only comprise a second connecting pipe 32, the second connecting pipe 32 connects the positive driving pump 11 and the negative driving pump 21, and the positive driving pump 11 is further used to drive all the negative electrolyte in the negative electrolyte tank 20 to flow into the positive electrolyte tank 10.

[0100] The driving device 3 can drive the negative electrolyte in the negative electrolyte tank 20 to flow into the positive electrolyte tank 10. When the driving device 3 is used to drive the negative electrolyte in the negative electrolyte tank 20 to flow into the positive electrolyte tank 10, the driving device 3 can comprise a mixing pump 30 and a first connecting pipe 31, the first connecting pipe 31 is communicated with the positive electrolyte tank 10 and the negative electrolyte tank 20, the mixing pump 30 is arranged on the first connecting pipe 31 and is used to drive all the negative electrolyte in the negative electrolyte tank 20 to flow into the positive electrolyte tank 10; or, the driving device 3 can only comprise a second connecting pipe 32, the second connecting pipe 32 connects the positive driving pump 11 and the negative driving pump 21, and the positive driving pump 11 is further used to drive all the negative electrolyte in the negative electrolyte tank 20 to flow into the positive electrolyte tank 10.

[0101] As an optional embodiment, the introducing device can comprise a reaction control device, the reaction control device is used to control the positive electrode to generate the reducing ion through the reduction reaction, and the reducing ion is reacted with the V2O5 precipitate in the positive electrolyte tank to generate the second composite electrolyte.

[0102] In the embodiment of the application, the reaction control device is used to control the positive electrode to generate the reducing ion through the reduction reaction, and the reducing ion is, for example, V 2+ , V 3+The V2O5 precipitate in the positive electrolyte tank is reduced to low-valence vanadium ions which are easily soluble, so as to remove the V2O5 precipitate in the positive electrolyte tank 10.

[0103] In the embodiments of the present application, the second composite electrolyte comprises a secondary reduction reaction product.

[0104] As a preferred embodiment, the reaction control device comprises a reverse connection device for controlling the circuit reverse connection of the positive electrode and the negative electrode.

[0105] In the embodiments of the present application, the reverse connection device can be a circuit reverse connection control device (not shown in the figure), which applies a reverse voltage to the battery (the positive electrode is connected to the negative electrode of the power supply, and the negative electrode is connected to the positive electrode of the power supply) to make the positive electrode produce a reduction reaction and the negative electrode produce an oxidation reaction.

[0106] In order to further understand the present application, the present application will be described below in conjunction with the embodiments, which are only used to illustrate the present application and do not limit the scope of the present application.

[0107] Embodiment 1: The Nafion 212, the graphite plate with a serpentine flow channel and the graphite felt are used as the basic structure for assembling the all-vanadium redox flow battery. The flow channel area is 16 cm 2 (4x4 cm 2 ), the gold-plated copper is used as the current collector, the electrolyte is a mixed solution of sulfuric acid with a valence of 3.5 and a total vanadium concentration of 1.7 mol / L, 40 mL of which is taken as the positive electrolyte and the negative electrolyte respectively, and the positive driving pump and the negative driving pump are the liquid supply devices for the positive electrode and the negative electrode of the flow battery respectively. The flow rate of the electrolyte in the test is 40 mL / min.

[0108] Firstly, the all-vanadium redox flow battery is placed in an oven with a temperature of 60°C to run for a period of time to observe the change of the positive electrolyte. As shown in FIG. 4(a) and FIG. 4(b), after the all-vanadium redox flow battery runs for a period of time in the environment with a temperature of 60°C, a large amount of V2O5 precipitate appears in the positive electrolyte, and the flow channel and the electrode inside the positive electrode are also full of V2O5 precipitate, which causes the positive electrolyte to fail to flow normally, resulting in energy loss and eventually leading to the failure of the battery.

[0109] Referring to FIG. 5(a), the state of the positive electrolyte tank and the negative electrolyte tank of the all-vanadium redox flow battery after the precipitation occurs.

[0110] Referring to FIG. 5(b), the negative electrolyte of the all-vanadium redox flow battery is driven to flow into the positive electrolyte tank to achieve the purpose of removing V2O5 in the positive electrolyte tank. Then, the electrolyte in the positive electrolyte tank is slowly pumped into the positive electrode side of the all-vanadium redox flow battery by the positive driving pump, so that the low-valence reducing V 2+ , V 3+The ions fully react with V2O5 to completely remove the V2O5 precipitate in the all-vanadium redox flow battery system.

[0111] Referring to Fig. 5(c), after the precipitate is removed, the remaining negative electrolyte of the all-vanadium redox flow battery is driven to flow into the positive electrolyte tank for full mixing, and the mixed electrolyte is redistributed to the positive electrolyte tank and the negative electrolyte tank to fully restore the capacity of the all-vanadium redox flow battery.

[0112] Example 2: The all-vanadium redox flow battery is assembled by using Nafion 212, a graphite plate with a serpentine flow channel, and a graphite felt as the basic structure. The flow channel has an area of 16 cm 2 (4x4 cm 2 ), gold-plated copper is used as the current collector plate, and the electrolyte is a 3.5-valent, 1.7 mol / L total vanadium concentration sulfuric acid mixed solution. 40 mL of the electrolyte is taken as the positive electrolyte and the negative electrolyte, respectively. The positive driving pump and the negative driving pump are the liquid supply devices for the positive and negative electrodes of the flow battery, respectively. The flow rate of the electrolyte in the test is 40 mL / min.

[0113] First, the all-vanadium redox flow battery is placed in an oven at a temperature of 60°C and operated for a period of time to observe the changes in the positive electrolyte. As shown in Fig. 4, after the all-vanadium redox flow battery is operated at 60°C for a period of time, a large amount of V2O5 precipitate appears in the positive electrolyte, and the flow channel and the electrode inside the positive electrode are also filled with V2O5 precipitate, causing the positive electrolyte to fail to flow normally.

[0114] Referring to Figure 3 , by reversing the positive and negative electrode circuits, the electrochemical method is used to generate V 2+ , V 3+ ions with reducing properties on the positive side of the all-vanadium redox flow battery, so that they fully react with V2O5 to achieve the purpose of removing the precipitate in the battery system.

[0115] Performance test The fresh battery before precipitation in Example 1 and the battery after precipitation are tested for discharge capacity and voltage efficiency. The test results of the discharge capacity are shown in Fig. 6(a), and the test results of the voltage efficiency are shown in Fig. 6(b).

[0116] The fresh battery before precipitation in Example 1 and the battery after mixing and redistribution of the liquid after precipitation are tested for discharge capacity and voltage efficiency. The test results of the discharge capacity are shown in Fig. 6(c), and the test results of the voltage efficiency are shown in Fig. 6(d).

[0117] The results show that after mixing and re-distribution, the V2O5 precipitate in the all-vanadium redox flow battery system can be completely removed without disassembling the stack and introducing new chemical components, and the battery voltage efficiency and discharge capacity are restored to the same performance as the fresh electrolyte. The method has the advantages of simple operation, low cost, good economic benefit, no special requirements for working environment, remarkable effect, etc., and is suitable for the field of all-vanadium redox flow battery.

[0118] The fresh battery before precipitation in Example 2 and the battery after positive and negative reversal were tested for discharge capacity and voltage efficiency. The test results of discharge capacity are shown in Figure 7(a), and the test results of voltage efficiency are shown in Figure 7(b).

[0119] The results show that after the positive and negative reversal, the discharge capacity and voltage efficiency of the battery after the positive and negative reversal are lower than those of the fresh battery in the first three cycles, but the discharge capacity and voltage efficiency of the battery are comparable to those of the fresh battery in the later period. It may be because, during the charging and discharging process, the battery treated by the positive and negative reversal method undergoes both electrochemical reaction and chemical reaction. During the charging and discharging process, the undissolved V2O5 continuously reacts with V 2+ and V 3+ during the charging and discharging process, consumes V 2+ , resulting in reduced cycle efficiency and discharge capacity. The slow dissolution of V2O5 increases the discharge capacity of the battery after cyclic use.

[0120] The above has described various embodiments of the present application, and the above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Many modifications and changes are obvious to those skilled in the art without departing from the scope and spirit of the described embodiments. The choice of terms used herein is intended to best explain the principles, practical applications, or improvements to the technology in the market of the embodiments, or to enable other ordinary skilled persons in the art to understand the embodiments disclosed herein.

Claims

1. A method for removing V2O5 precipitation in an all-vanadium redox flow battery, characterized in that: include: S1. Introducing reducing ions into the positive electrode through an introduction device, so that the reducing ions react with the V2O5 precipitate at the positive electrode to remove the V2O5 precipitate at the positive electrode.

2. The method according to claim 1, characterized in that Said S1 comprises: S10, driving at least part of the negative electrode electrolyte in the negative electrode storage tank to flow into the positive electrode storage tank through the driving device 3, so that the reducing ions in the negative electrode electrolyte enter the positive electrode storage tank, and the reducing ions react with the V2O5 precipitation in the positive electrode storage tank to generate a first composite electrolyte; or, S20, controlling the positive electrode to undergo a reduction reaction by a reaction control device to generate reducing ions, and causing the reducing ions to react with the V2O5 precipitate in the positive electrode storage tank to generate a second composite electrolyte.

3. The method according to claim 2, characterized in that After S10, the method further includes: S11, driving the first composite electrolyte in the positive electrode storage tank to flow into the positive electrode side through a positive electrode driving pump to remove V2O5 precipitation on the positive electrode side; S12, driving all the remaining negative electrode electrolyte in the negative electrode storage tank to flow into the positive electrode storage tank, and mixing all the electrolytes in the positive electrode storage tank to obtain a first mixed electrolyte; S13, driving the first mixed electrolyte in the positive electrode liquid storage tank to be distributed into the negative electrode liquid storage tank.

4. The method according to claim 3, characterized in that In the S10, the electrolyte is driven to flow by a mixing pump or a cathode drive pump; and / or, in the S12, the electrolyte is driven to flow by a mixing pump or a cathode drive pump; and / or, in the S13, the electrolyte is driven to flow by a mixing pump or a cathode drive pump.

5. The method according to claim 2, characterized in that The S20 includes: S200, the polarity of the positive electrode and the negative electrode is reversed by a reverse connection device, so that a reduction reaction occurs at the positive electrode to generate reducing ions.

6. The method according to claim 5, characterized in that: The S200 includes: reversing the circuits of the positive and negative electrodes by a reverse connection device; and / or, After S200, the method further includes: Monitor the dissolution state of the V2O5 precipitate in the positive electrode; control the circuit reverse connection duration based on the performance parameters of the electrolyte and the dissolution state of the V2O5 precipitate in the positive electrode.

7. The method according to claim 1, characterized in that The reducing ions include V 2+ 、V 3+ At least one ion in.

8. An all-vanadium liquid flow battery system, characterized in that: include: An all-vanadium liquid flow battery, comprising a positive electrode, a negative electrode, and a diaphragm, wherein the positive electrode comprises a positive electrode liquid storage tank, a positive electrode drive pump, and a positive electrode side electrode, wherein the positive electrode drive pump is used to pump the positive electrode electrolyte in the positive electrode liquid storage tank into the positive electrode side electrode; the negative electrode comprises a negative electrode liquid storage tank, a negative electrode drive pump, and a negative electrode side electrode, wherein the negative electrode drive pump is used to pump the negative electrode electrolyte in the negative electrode liquid storage tank into the negative electrode side electrode; An introduction device is connected to the positive electrode and the negative electrode and is used to introduce reducing ions into the positive electrode, so that the reducing ions react with the V2O5 precipitate at the positive electrode to remove the V2O5 precipitate at the positive electrode.

9. The all-vanadium liquid flow battery system according to claim 8, characterized in that: The introduction device includes a driving device, which is used to drive the negative electrode electrolyte in the negative electrode storage tank to flow into the positive electrode storage tank, so that the reducing ions in the negative electrode electrolyte enter the positive electrode storage tank, and cause the reducing ions to react with the V2O5 precipitation in the positive electrode storage tank to generate a first composite electrolyte; or, the introduction device includes a reaction control device, which is used to control the positive electrode to undergo a reduction reaction to generate reducing ions, so that the reducing ions react with the V2O5 precipitation in the positive electrode storage tank to generate a second composite electrolyte.

10. The all-vanadium liquid flow battery system according to claim 9, characterized in that: The driving device includes a mixing pump and a first connecting pipe, the first connecting pipe is connected to both the positive electrode storage tank and the negative electrode storage tank, the mixing pump is arranged on the first connecting pipe, and is used to drive the negative electrode electrolyte in the negative electrode storage tank to flow into the positive electrode storage tank; or, the driving device includes a first connecting pipe, the first connecting pipe connects the positive electrode driving pump and the negative electrode driving pump, and the negative electrode driving pump is also used to drive the negative electrode electrolyte in the negative electrode storage tank to flow into the positive electrode storage tank; or, The reaction control device includes a reverse connection device, which is used to control the reverse connection of the positive and negative circuits.

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