A separator for an aqueous flow battery and the battery thereof.

Abstract

This invention provides a separator and battery for an aqueous flow battery, belonging to the field of energy storage batteries. It comprises a homogeneous organic phase formed by liquid organic compounds and ionic compounds, which is immiscible with the aqueous electrolyte. The solubility of the positive and negative electrode active materials in the aqueous electrolyte is much greater than their solubility in the organic phase. Ions in the organic phase also have a certain solubility in the positive and negative electrode aqueous electrolytes, allowing them to shuttle between the three phases: positive electrode aqueous electrolyte / organic phase / negative electrode aqueous electrolyte. The separator is positioned between the positive and negative electrode aqueous electrolytes, preventing the active materials in the electrolyte from traversing the membrane. This invention also provides a battery comprising the above separator. The separator prepared by this invention utilizes the liquid-liquid phase separation phenomenon between the organic and aqueous phases to construct an ion-selective conductive separator. Its preparation process is simple and its application range is wide.

Description

Technical Field

[0001] This invention belongs to the field of energy storage batteries, and more specifically, relates to a separator for an aqueous flow battery and the battery thereof. Background Technology

[0002] With the introduction of the "dual carbon" target, my country needs to vigorously promote the development of clean energy. Solar and wind power, among other renewable energy sources, are important components of future energy development. However, the intermittent and unstable nature of renewable energy poses challenges to the stability and security of the power system. Energy storage technology, as an important technological means, can help achieve the efficient utilization of new energy power generation and the stable operation of the power system after new energy power generation is connected to the grid.

[0003] Current mainstream energy storage technologies mainly include pumped hydro storage, compressed air storage, and electrochemical energy storage. Among them, electrochemical energy storage has attracted market and industry attention due to its flexible site selection and wide applicability. Lithium-ion batteries, with their long lifespan and high energy density, are currently the most widely used energy storage battery. However, the limited natural reserves of lithium, complex manufacturing processes, and the highly flammable nature of their internal electrolytes limit their development in large-scale energy storage. Lead-acid batteries, although commercialized for a longer period and with lower costs, are inferior to lithium-ion batteries in terms of energy density and cycle stability. In contrast, flow batteries decouple capacity and power, offering advantages such as higher environmental adaptability, higher safety, and longer cycle life, and are considered one of the most promising large-scale energy storage technologies.

[0004] A typical flow battery consists of aqueous electrolytes for positive and negative electrodes, a separator, bipolar plates, porous electrodes, and end plates, along with an external pump and a storage tank. During charging and discharging, the aqueous electrolytes for positive and negative electrodes are transported into the battery by a peristaltic pump. Redox reactions occur on the surface of the porous electrodes (such as graphite felt), and certain ions in the aqueous electrolytes migrate between the positive and negative electrodes through the separator, thus achieving charging and discharging. The amount of energy stored in a flow battery depends on the size of the external storage tank, while the maximum charge / discharge power depends on the size of the stack consisting of the separator, bipolar plates, and porous electrodes. Therefore, independent design and adjustment of battery power and capacity are possible, giving it advantages in power system energy storage.

[0005] The separator is a key component of a flow battery. It possesses selective ion conductivity, separating redox active materials in the positive and negative electrolytes while also conducting ions during charging and discharging to form a closed loop with the external circuit, enabling energy storage and release. The transmembrane shuttle of redox active materials leads to a decrease in coulombic efficiency, capacity decay, and reduced cycle life. Therefore, the ion conductivity selectivity and ionic conductivity of the separator largely determine the performance of the flow battery.

[0006] Currently, the ion conductivity selectivity of membranes is mainly based on the micropore design of solid-state ion-conducting materials. Taking a vanadium redox flow battery as an example, the redox active materials in the aqueous electrolyte of the positive electrode are tetravalent vanadium ions and pentavalent vanadium ion redox pairs (V₂O₃O₃O₄ ... 2+ / VO2 + The redox active substances in the aqueous electrolyte at the negative electrode are divalent vanadium ions and trivalent vanadium ion redox pairs (V0 and V1). 2+ / V 3+ The vanadium redox flow battery uses sulfuric acid (H₂SO₄) as the supporting electrolyte. Typically, the separator in a vanadium redox flow battery is made of polymer, where the polymer backbone provides mechanical structural support, and the ionic side chain groups enable the separator to conduct ions. During charging and discharging, the aqueous electrolytes for both the positive and negative electrodes flow through the battery interior under the pump's pressure. The redox active materials in the aqueous electrolytes for both electrodes undergo redox reactions on the electrode surfaces. During charging, the redox active material V₂O₃ in the aqueous electrolyte at the positive electrode... 2+ Oxidized into VO2 + The electrolyte color changed from blue to yellow, while the redox active substance V in the negative electrode aqueous electrolysis... 3+ Restored to V 2+ The electrolyte color changed from green to purple, H + The separator facilitates the movement of redox active materials between the positive and negative aqueous electrolytes, maintaining charge balance within the battery. During discharge, the reactions proceed in the opposite direction. If redox active materials in the positive and negative aqueous electrolytes shuttle across the membrane during charging and discharging, it will lead to reduced charge / discharge efficiency, capacity decay, and decreased cycle life. Therefore, improving the selective conduction of redox active materials and shuttle ions by the separator is crucial.

[0007] Among them, Nafion membranes have a wide range of applications in vanadium redox flow batteries. Although they have high proton conductivity, they are not very selective for redox active material vanadium ions, resulting in low charge and discharge efficiency. Therefore, researchers often introduce inorganic materials and polymers to adjust pore size and channels to reduce the diffusion of vanadium ions [L.Yu,F.Lin,L.Xu,J.Xi.A recast Nafion / graphene oxide composite membrane for advanced vanadium redox flow batteries.RSC Advances,2016,6(5):3756-3763],[J.Ye,D.Yuan,M.Ding,Y.Long,T.Long,L.Sun et al.A cost-effective nafion / lignin compositemembrane with low vanadium ion permeation for high performance vanadium redoxflow battery.Journal of Power Sources,2021,482:]. In addition, zeolite molecular sieves are microporous materials with ion conductivity, with pore sizes between 0.3-1 nm. Their multidimensional and tunable channel network can accurately control the pore size. The pore size of ZSM-35 (0.35-0.54 nm) is between the size of hydrated hydrogen ions (<0.24 nm) and hydrated vanadium ions (>0.6 nm). Researchers combined it with a porous support membrane to form a composite membrane with high ion selectivity, which can reduce the self-discharge of the battery [Z.Yuan,X.Zhu,M.Li,W.Lu,X.Li,H.Zhang.A Highly Ion-SelectiveZeolite Flake Layer on Porous Membranes for Flow Battery Applications.AngewChem Int Ed Engl,2016,55(9):3058-3062]. The above modifications are all based on micropore design to adjust the pore size and channels in the membrane, which improves the selective conduction of ions by the membrane to a certain extent. However, the process is relatively complex and the applicability of the system is not high.

[0008] Therefore, there is a need to develop a new type of separator for aqueous flow batteries that can reduce the process complexity of existing technologies and has good system applicability. Summary of the Invention

[0009] To address the shortcomings of existing technologies, the present invention aims to provide a separator and battery for aqueous flow batteries. The separator design is novel, utilizing the liquid-liquid phase separation phenomenon of the organic and aqueous phases to construct an ion-selective conductive separator. The selective ion conduction mechanism of this separator is based on the differences in solubility of the positive and negative electrode redox active materials and shuttle ions in different liquid phases. The present invention effectively solves the problems of complex processes and narrow system applicability in the selective ion conduction of separators in existing technologies, and overturns traditional technical concepts.

[0010] To achieve the above objectives, a first aspect of the present invention provides a separator for an aqueous flow battery, comprising an inert porous organic membrane and an ion-conducting organic liquid impregnated in the inert porous organic membrane, wherein the ion-conducting organic liquid is in a liquid state and has ion-conducting function.

[0011] Ion-conducting organic liquids are formed by dissolving ionic compounds in organic compounds. These liquids contain free charged groups or ions. These charged groups or ions can simultaneously dissolve in both the negative and positive aqueous electrolytes, allowing them to move freely within these electrolytes and thus enabling electrochemical reactions and forming the battery circuit.

[0012] The redox substances in the negative electrode aqueous electrolyte and the positive electrode aqueous electrolyte are insoluble or only slightly soluble in organic compounds, and the negative electrode aqueous electrolyte and the positive electrode aqueous electrolyte as a whole are immiscible with the ion-conducting organic liquid.

[0013] Furthermore, the ionic compound is at least one of bis(trifluoromethanesulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, bis(nonafluorobutylsulfonyl)imide, and sodium bis(nonafluorobutylsulfonyl)imide.

[0014] Furthermore, the organic compound is one or more of tetraethylene glycol dimethyl ether, diethylene glycol dibutyl ether, ethylene glycol dibutyl ether, and diethylene glycol diethyl ether.

[0015] Furthermore, the concentration of ionic compounds in the ion-conducting organic liquid is 0.1 mol / L to 3 mol / L.

[0016] Furthermore, the inert porous organic membrane has a greater wettability to organic phases than to aqueous electrolytes for both the negative and positive electrodes, preferentially wetting the ion-conducting organic liquid. Its material is a porous polyethylene membrane or a porous polypropylene membrane.

[0017] According to a second aspect of the present invention, a separator for an aqueous flow battery is also provided. This separator is a gel membrane formed from cross-linked polymers possessing mechanical strength. The cross-linked polymers provide structural support, enabling the gel membrane to appear as a solid macroscopically. At the microscopic level, the gel contains an ion-conducting organic liquid, which is in a liquid state and possesses ion-conducting functionality.

[0018] Ion-conducting organic liquids are formed by dissolving ionic compounds in organic compounds. These liquids contain free charged groups or ions with ion-conducting capabilities. These charged groups or ions can simultaneously dissolve in both the negative and positive aqueous electrolytes, and can move freely within these electrolytes.

[0019] The redox substances in the negative electrode aqueous electrolyte and the positive electrode aqueous electrolyte are insoluble or only slightly soluble in organic compounds, and the negative electrode aqueous electrolyte and the positive electrode aqueous electrolyte as a whole are immiscible with the ion-conducting organic liquid.

[0020] Furthermore, the cross-linked polymer is cross-linked polypropylene oxide or cross-linked polyethylene oxide.

[0021] According to a second aspect of the invention, an aqueous flow battery comprising a diaphragm as described above is also provided.

[0022] Furthermore, it is one of the following: vanadium redox flow battery, zinc-bromine flow battery, and zinc-iron flow battery.

[0023] Furthermore, a separator is placed between the positive and negative aqueous electrolytes of the aqueous flow battery to prevent the cross-membrane shuttle of redox substances in the positive and negative aqueous electrolytes, while selectively conducting ions, thereby forming a loop with the external circuit.

[0024] In summary, compared with the prior art, the above-described technical solutions conceived by this invention have the following advantages:

[0025] Beneficial effects:

[0026] In the inventive concept of this application, the separator achieves two-phase separation between the positive electrode aqueous electrolyte and the negative electrode aqueous electrolyte and the organic phase in the separator through a liquid-liquid phase separation method. The inert porous membrane wetted by the organic phase provides mechanical support strength to the separator. The solubility of the positive and negative electrode redox active materials in the positive and negative electrode aqueous electrolytes is much greater than their solubility in the organic phase, ensuring that the positive and negative electrode redox active materials in the positive and negative electrode aqueous electrolytes do not enter the organic phase (the organic phase in this invention is the ion-conducting organic liquid), inhibiting the transmembrane diffusion of the positive and negative electrode redox active materials, thereby improving the charge and discharge efficiency of the battery.

[0027] The separator for aqueous flow batteries provided by this invention does not require micropore design to achieve selective ion permeation. It can achieve a separator with high ionic conductivity, high ion selective permeability, and high cycle life through a simple manufacturing process, thereby improving the charge and discharge efficiency and cycle life of flow batteries and facilitating their application in large-scale energy storage. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the diaphragm structure in an embodiment of the present invention;

[0029] Figure 2 These are schematic diagrams of the battery structure in Embodiments 1, 2, 3, 4 and Comparative Example 1 of this application.

[0030] Figure 3 This is a charge-discharge cycle performance diagram of Embodiment 1 of the present invention;

[0031] Figure 4 This is a charge-discharge cycle performance diagram of Comparative Example 1 of the present invention;

[0032] Figure 5a and Figure 5b These are the molecular structures of bis(trifluoromethanesulfonyl)imide and lithium(bis(trifluoromethanesulfonyl)imide) in the examples, respectively.

[0033] Figure 6a and Figure 6b These are the molecular structures of bis(nonafluorobutylsulfonyl)imine and sodium bis(nonafluorobutylsulfonyl)imine, respectively.

[0034] Among them, O in the above attached figures A and R A These represent the oxidized and reduced states of the active material molecules in the positive electrode electrolyte, respectively. C and R C M represents the oxidized and reduced states of the active substance molecules in the negative electrode electrolyte, respectively. m+ These are the ions that are conducted in the positive electrode aqueous electrolyte / organic phase / negative electrode aqueous electrolyte. Detailed Implementation

[0035] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0036] This invention provides a separator and battery for an aqueous flow battery. The separator design concept is novel. It utilizes the liquid-liquid phase separation phenomenon of the organic phase and the aqueous phase to construct an ion-selective conductive separator. The selective ion conduction mechanism of this separator is different from that of previous ion-selective membranes. It no longer relies on the microporous structure in the solid ion conduction material, but is based on the difference in solubility of the positive and negative electrode redox active materials and shuttle ions in different liquid phases.

[0037] This invention provides two types of membranes. One type includes an inert porous organic membrane and an ion-conducting organic liquid impregnated within the inert porous organic membrane. This design is based on the fact that the inert porous organic membrane can provide mechanical support for the organic phase (the organic phase refers to the ion-conducting organic liquid), and its pore size can be much larger than the molecular size of the active substances (active substances refer to substances in the positive and negative electrode electrolytes that can undergo redox reactions; in a full vanadium electrolyte flow, these are vanadium ions; in zinc-iron electrolytes, they are iron and zinc ions; and in zinc-bromine electrolytes, they are zinc and bromide ions). The inert porous organic membrane has a greater wetting capacity for the organic phase than for both the negative and positive aqueous electrolytes, preferentially wetting the ion-conducting organic liquid. Its material is a porous polyethylene membrane or a porous polypropylene membrane. Another type of separator is a gel membrane formed from cross-linked polymers with mechanical strength. The cross-linked polymers provide structural support, making the gel membrane appear solid macroscopically. The cross-linked polymers are cross-linked polypropylene oxide or cross-linked ethylene oxide. At the microscopic level, the gel contains an ion-conducting organic liquid, which is liquid and possesses ion-conducting capabilities. This ion-conducting organic liquid is formed by dissolving ionic compounds in organic compounds, containing free charged groups or ions with ion-conducting functions. These charged groups or ions can simultaneously dissolve in both the negative and positive aqueous electrolytes, allowing them to move freely within these electrolytes, thus enabling the electrochemical reactions of the battery and forming the battery circuit. The redox substances in the negative electrode aqueous electrolyte and the positive electrode aqueous electrolyte are insoluble or only slightly soluble in organic compounds, and the negative electrode aqueous electrolyte and the positive electrode aqueous electrolyte as a whole are immiscible with the ion-conducting organic liquid.

[0038] The redox active materials of the positive and negative electrodes in the flow battery have a much higher solubility in the aqueous electrolytes than in the organic phase. This design prevents the redox active materials in the aqueous electrolyte from diffusing into the organic phase, and vice versa, ensuring no contact between the active materials in the aqueous electrolytes. The organic phase possesses ion conductivity and has at least one conductive ion or charged group. It also has a certain solubility in both the aqueous electrolytes and can move between the three phases: the aqueous electrolyte, the organic phase, and the aqueous electrolyte. This design ensures selective ion conductivity in the organic phase. The ionic compound is at least one of bis(trifluoromethanesulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, bis(nonafluorobutylsulfonyl)imide, and sodium bis(nonafluorobutylsulfonyl)imide. Among the amines mentioned above, because the central nitrogen atom is attached to the electron-withdrawing groups trifluoromethanesulfonyl and nonafluorobutylsulfonyl, the hydrogen atoms become very easily dissociated, thus bis(trifluoromethanesulfonyl)imide and bis(nonafluorobutylsulfonyl)imide exhibit strong acidity. The organic compound is one or more of tetraethylene glycol dimethyl ether, diethylene glycol dibutyl ether, ethylene glycol dibutyl ether, and diethylene glycol diethyl ether. The concentration of the ionic compound in the ion-conducting organic liquid is 0.1 mol / L to 3 mol / L.

[0039] When using the above-described membrane to fabricate an aqueous flow battery, the membrane is positioned between the positive and negative aqueous electrolytes. It prevents the cross-membrane shuttle of redox substances in both electrolytes while selectively conducting ions, thus forming a circuit with an external circuit. Common aqueous flow batteries include vanadium redox flow batteries, zinc-bromine flow batteries, and zinc-iron flow batteries.

[0040] The following is a more detailed explanation with reference to specific embodiments.

[0041] Example 1

[0042] Example 1 is a liquid separator in a vanadium redox flow battery.

[0043] In this embodiment, the liquid organic compound and ionic compound constituting the organic phase are diethylene glycol dibutyl ether and lithium bis(trifluoromethanesulfonyl)imide. Specifically, 4.31 g of lithium bis(trifluoromethanesulfonyl)imide is dissolved in 10 mL of diethylene glycol dibutyl ether solvent as the organic phase. The aqueous electrolyte at the positive electrode contains 1.7 mol / L VO2. 2+ A mixed solution of 3 mol / L H2SO4 and an aqueous negative electrode electrolyte containing 1.7 mol / L VO2SO4. 2+A mixed solution of 3 mol / L H₂SO₄ and 1 mol / L lithium sulfate were added to both the positive and negative electrode aqueous electrolytes, so that Li₂ is present in all three phases: the organic phase and the positive and negative electrode aqueous electrolytes. + Li + It can move between the three phases, ensuring the ionic conductivity of the intermediate organic phase. An appropriate amount of organic phase is dropped onto a porous polypropylene membrane, which is then used as the separator for a vanadium redox flow battery. A schematic diagram of the separator's operation is shown below. Figure 1 As shown, Figure 1 This is a schematic diagram of the diaphragm structure in an embodiment of the present invention. As shown in the figure, a 3cm×3cm graphite felt is used as a porous electrode in the vanadium redox flow battery. Before use, it is activated by soaking in the positive and negative aqueous electrolytes for 12 hours respectively. The positive and negative aqueous electrolytes in the storage tank are electrolytes after phase separation by mixing with the organic phase. They are in a saturated state of the organic phase, and the organic phase and the aqueous phase are in a thermodynamically stable state.

[0044] Assemble the battery using the separator prepared above. The battery structure is shown in Figure 2. Figure 2 This is a schematic diagram of the battery structure in Embodiments 1, 2, 3, and 4 of this invention application, as well as Comparative Example 1. As shown in the diagram, after static testing, once the positive and negative electrode aqueous electrolytes fill the battery graphite felt, the peristaltic pump stops pumping liquid into the battery. The charge / discharge cutoff voltage is set to 0.8-1.65V. Figure 3 This is a charge-discharge cycle performance diagram of Embodiment 1 of the present invention. As can be seen from the diagram, the battery performs well at 10 mA / cm². 2 After 200 cycles at a current density, the coulombic efficiency remains above 97%.

[0045] Comparative Example 1

[0046] Commercial Nafion 115 ion-exchange membranes were used as the separator for the vanadium redox flow battery. Using the same aqueous electrolytes for both positive and negative electrodes as in Example 1, the Nafion 115 membrane required pretreatment before use. First, it was heated at 80°C for 1 hour in a 5% (w / w) hydrogen peroxide solution, then at 80°C for 1 hour in deionized water, followed by heating at 80°C for 1 hour in a 1 mol / L sulfuric acid solution, and finally at 80°C for 1 hour in deionized water. After treatment, it was soaked in deionized water for later use.

[0047] The battery structure is the same as in Example 1. Before charging and discharging, argon gas is slowly introduced into the positive and negative aqueous electrolytes in the storage tank to remove oxygen, preventing the V in the negative aqueous electrolyte from being affected during charging. 2+ This caused an impact. Charge and discharge tests were performed on the battery, with the charge / discharge cutoff voltage set to 0.8-1.65V and the current density at 10mA / cm². 2 , Figure 4This is a charge-discharge cycle performance diagram of Comparative Example 1 of the present invention, based on... Figure 4 The battery charge-discharge cycle performance results shown are at 10 mA / cm 2 After 100 cycles at a current density, the coulombic efficiency is 90%.

[0048] Example 2

[0049] Example 2 describes a gel membrane used in a vanadium redox flow battery. Diethylene glycol diethyl ether is used as the liquid organic compound, and bis(nonafluorobutylsulfonyl)imide is used as the ionic compound. Specifically, 1.5 mol / L bis(nonafluorobutylsulfonyl)imide is dissolved in 10 mL of ethylene glycol dibutyl ether solution as the organic phase. 5 wt% polypropylene glycol (PPG) is dissolved in the organic phase as a crosslinking polymer, and hexamethylene diisocyanate trimer (HDIt) is used as a crosslinking agent, wherein the molar ratio of hydroxyl groups (-OH) in PPG to isocyanate groups (-NCO-) in HDIt is 1:1. The organic phase containing PPG and HDIt is stirred magnetically to form a homogeneous solution. An appropriate amount of dibutyltin dilaurate is added, and the mixture is stirred at 60°C for 20 minutes. A polypropylene porous membrane is then immersed in the organic phase. After complete wetting, the membrane is transferred to a polytetrafluoroethylene plate and heated at 80°C for 3 hours to form a gel membrane. This design utilizes the cross-linked structure of the polymer to stabilize the organic phase, maintaining stability under the disturbance of the flowing electrolyte, thereby improving the cycle stability of the battery. Bis(nonafluorobutylsulfonyl)imide dissolved in ethylene glycol diethyl ether ionizes to release hydrogen ions (H+). + Therefore, in this embodiment, during the battery charging and discharging process, H + It shuttles between the positive and negative electrolytes.

[0050] Using a gel membrane as the separator in a vanadium redox flow battery, according to... Figure 2 The battery structure shown is assembled with the same aqueous electrolyte for positive and negative electrodes and porous electrodes as in Example 1. This battery operates at 60 mA / cm². 2 At a current density, it can stably cycle for more than 200 times, with a coulombic efficiency of over 95%.

[0051] Example 3

[0052] Example 3 is a liquid membrane in a zinc-iron flow battery.

[0053] The preparation process of the membrane is similar to that in Example 1. The liquid organic compound in the organic phase is tetraethylene glycol dimethyl ether, and the ionic compound is sodium bis(nonafluorobutylsulfonyl)imide, specifically, the concentration of sodium bis(nonafluorobutylsulfonyl)imide is 3 mol / L. The organic phase is mixed with a 4 mol / L sodium hydroxide (NaOH) solution, and the inert porous membrane wetted by the phase-separated organic phase is a polyethylene porous membrane. 0.49 g of zinc oxide powder is dissolved in a 4 mol / L NaOH solution as the negative electrode aqueous electrolyte, and 2.53 g of potassium ferrocyanide (K4Fe(CN)6) is dissolved in a 4 mol / L NaOH solution as the positive electrode aqueous electrolyte. Before use, the positive and negative electrode aqueous electrolytes are mixed with the organic phase, and the phase-separated electrolyte is placed in a storage tank. Inert gas is slowly introduced into the positive electrode aqueous electrolyte in the storage tank to remove oxygen and avoid the influence of oxygen on divalent iron. During charging, the ferrocyanide Fe(CN)6 ions in the aqueous electrolyte at the positive electrode... 4- It is oxidized to ferricyanide (Fe(CN)6) 3- The tetrahydroxyzinc ions (Zn(OH)) in the aqueous electrolyte at the negative electrode 4- It is reduced to zinc (Zn), Na + As shuttle ions, they are conducted between the positive and negative electrodes, the aqueous electrolyte, and the organic phase. When the battery is discharged, the process is reversed.

[0054] Battery structure such as Figure 2 As shown, at 60mA / cm 2 The battery was tested at a current density of 1.3V-1.9V, and no significant capacity decay was observed after 200 cycles.

[0055] Example 4

[0056] Example 4 illustrates an application of a zinc-bromine flow battery. 2 mol / L bis(trifluoromethanesulfonyl)imide, as an ionic compound, is added to 10 mL of ethylene glycol dibutyl ether liquid organic compound to form a homogeneous organic phase. A polyethylene porous membrane, as an inert porous membrane, provides structural support for the organic phase. The aqueous electrolytes for the positive and negative electrodes are a mixed solution of 2 mol / L zinc bromide (ZnBr2) and 4 mol / L potassium chloride (KBr). Graphite felt is used as the porous electrode, and the polyethylene porous membrane impregnated with the organic phase serves as the separator. Before use, the mixed solution of 2 mol / L zinc bromide (ZnBr2) and 4 mol / L potassium chloride (KBr) needs to be mixed with the organic phase to saturate it. The electrolyte after phase separation is used as the aqueous electrolyte for the positive and negative electrodes. Figure 1 The battery structure shown was assembled and its performance tested. The charge / discharge cutoff voltage was set to 0.6V-2V at 40mA / cm. 2 At a given current density, the battery can stably cycle 200 times.

[0057] In Example 1 and Comparative Example 1, lithium bis(trifluoromethanesulfonyl)imide was used; in Example 4, bis(trifluoromethanesulfonyl)imide was used; in Example 2, bis(nonafluorobutylsulfonyl)imide was used; and in Example 3, sodium bis(nonafluorobutylsulfonyl)imide was used. Figure 5a and Figure 5b These are the molecular structures of bis(trifluoromethanesulfonyl)imide and lithium(bis(trifluoromethanesulfonyl)imide) in the examples, respectively. Figure 6a and Figure 6b These are the molecular structures of bis(nonafluorobutylsulfonyl)imine and sodium bis(nonafluorobutylsulfonyl)imine, respectively.

[0058] In the above embodiments, the concentration of the ionic compound in the ion-conducting organic liquid is 0.1 mol / L to 3 mol / L. This concentration can be flexibly configured, adjusted, and selected as needed.

[0059] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A separator for aqueous flow batteries, characterized in that, It comprises an inert porous organic membrane and an ion-conducting organic liquid infiltrated in the inert porous organic membrane, the ion-conducting organic liquid is in a liquid state, and the ion-conducting organic liquid has an ion-conducting function, The ion-conducting organic liquid is formed by dissolving an ionic compound in an organic compound, wherein free charged groups or ions are present, the charged groups or ions in the ion-conducting organic liquid can be simultaneously dissolved in the negative aqueous electrolyte and the positive aqueous electrolyte, and the charged groups or ions can shuttle in the ion-conducting organic liquid, the negative aqueous electrolyte and the positive aqueous electrolyte, The redox substances in the negative aqueous electrolyte and the positive aqueous electrolyte are insoluble or slightly soluble in the organic compound, and the negative aqueous electrolyte and the positive aqueous electrolyte as a whole are immiscible with the ion-conducting organic liquid, The ionic compound is at least one of bis-trifluoromethanesulfonylimide, lithium bis-trifluoromethanesulfonylimide, bis(nonafluorobutylsulfonyl)imide, and sodium bis(nonafluorobutylsulfonyl)imide. The organic compound is one or more of tetraethylene glycol dimethyl ether, diethylene glycol dibutyl ether, ethylene glycol dibutyl ether, and diethylene glycol diethyl ether. The inert porous organic membrane has a greater infiltrating capacity for the organic phase than for the negative aqueous electrolyte and the positive aqueous electrolyte.

2. A separator for aqueous flow batteries as claimed in claim 1 characterised in that, The concentration of the ionic compound in the ion-conducting organic liquid is 0.1 mol / L to 3 mol / L.

3. A separator for aqueous flow batteries as defined in claim 2, characterized in that The inert porous organic membrane preferentially infiltrates the ion-conducting organic liquid, and the material thereof is a porous polyethylene membrane or a porous polypropylene membrane.

4. A separator for aqueous flow batteries, characterized in that, It is a gel membrane formed by cross-linked polymers with mechanical strength, and the cross-linked polymers play a role in structural support, so that the gel membrane appears as a solid in the macroscopic view, and in the microscopic view, the gel contains an ion-conducting organic liquid, the ion-conducting organic liquid is in a liquid state, and the ion-conducting organic liquid has an ion-conducting function, The ion-conducting organic liquid is formed by dissolving an ionic compound in an organic compound, wherein free charged groups or ions are present, the charged groups or ions in the ion-conducting organic liquid can be simultaneously dissolved in the negative aqueous electrolyte and the positive aqueous electrolyte, and the charged groups or ions can shuttle in the ion-conducting organic liquid, the negative aqueous electrolyte and the positive aqueous electrolyte, The redox substances in the negative aqueous electrolyte and the positive aqueous electrolyte are insoluble or slightly soluble in the organic compound, and the negative aqueous electrolyte and the positive aqueous electrolyte as a whole are immiscible with the ion-conducting organic liquid, The ionic compound is at least one of bis-trifluoromethanesulfonylimide, lithium bis-trifluoromethanesulfonylimide, bis(nonafluorobutylsulfonyl)imide, and sodium bis(nonafluorobutylsulfonyl)imide. The organic compound is one or more of tetraethylene glycol dimethyl ether, diethylene glycol dibutyl ether, ethylene glycol dibutyl ether, and diethylene glycol diethyl ether. The cross-linked polymers are cross-linked polypropylene oxide or cross-linked polyethylene oxide.

5. A water-based flow battery comprising the separator membrane according to any one of claims 1-4.

6. The aqueous flow battery of claim 5, wherein, It is one of a full vanadium redox flow battery, a zinc-bromine flow battery, and a zinc-iron flow battery.

7. The aqueous flow battery of claim 6, wherein, The diaphragm is arranged between the positive aqueous electrolyte and the negative aqueous electrolyte of the water-based flow battery, and is used for preventing the transmembrane shuttling of the redox material in the positive aqueous electrolyte and the negative aqueous electrolyte, and can selectively conduct ions, so as to form a loop with the external circuit.

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