Heterogeneous polyelectrolyte self-assembly film, preparation method and application thereof

Abstract

This invention relates to a heterogeneous polyelectrolyte self-assembled membrane, its preparation method, and its applications. During the flow of electrolyte in a flow battery, a polyanionic complex in one side of the electrolyte and a polycationic complex in the other side self-assemble on a glass fiber substrate through strong electrostatic adsorption to form the separator of the flow battery, namely, the heterogeneous polyelectrolyte self-assembled membrane. This membrane not only possesses excellent mechanical properties and ionic conductivity, but its microporous structure effectively inhibits the interpenetration and mixing of redox-active molecules in the flow battery. An aqueous flow battery system assembled with this heterogeneous polyelectrolyte self-assembled membrane and typical redox-active organic molecules retains more than 97% of its initial capacity after 2000 charge-discharge cycles. Compared with existing technologies, the heterogeneous polyelectrolyte self-assembled membrane of this invention can effectively suppress capacity decay caused by the permeation and cross-mixing of redox-active molecules in the electrolyte through the membrane in aqueous flow batteries.

Description

Technical Field

[0001] This invention relates to the field of electrochemical energy storage technology, and in particular to a heterogeneous polyelectrolyte self-assembled membrane, its preparation method, and its application. Background Technology

[0002] Aqueous flow batteries have shown great promise in the energy storage field due to their safety, environmental friendliness, and scalability. Using water as the electrolyte solvent, aqueous flow batteries are non-flammable and have low toxicity, while avoiding the use of organic solvents and transition metals, thus reducing environmental pollution. The energy and power of aqueous flow batteries can be designed independently, making them suitable for large-scale energy storage.

[0003] With the rapid development of aqueous flow batteries, the use of organic redox active molecules with fast electrochemical reaction kinetics and low cost to replace vanadium-based materials or other transition metals has been widely studied and reported. Although redox active materials exhibit good electrochemical reversibility in aqueous flow batteries, cycle stability is still limited by the separator. The permeation and cross-mixing of redox active molecules through the separator leads to battery capacity decay, which is a key factor affecting the cycle stability of flow batteries.

[0004] In aqueous flow batteries, the separator must not only achieve efficient ion transport but also prevent cross-penetration and mixing of redox-active molecules. Therefore, a trade-off must be struck between a range of properties, including ionic conductivity, selective permeability, and mechanical stability, to achieve a high-capacity, long-life aqueous flow battery. High ionic conductivity typically requires a larger pore size and higher porosity, but this increases the risk of redox-active molecule permeation. The separator needs sufficient mechanical strength to withstand the physical and chemical stresses during long-term operation. The separator material must also have good chemical compatibility with the electrolyte and redox-active molecules to prevent degradation or performance decline.

[0005] Previously, there have been many reports on reducing the penetration and cross-mixing of redox active molecules through the functional design of membranes, but problems such as complex membrane preparation processes and high costs still exist, and the compatibility issues between electrolyte / membrane systems and redox active molecules also need to be solved. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of the prior art by providing a heterogeneous polyelectrolyte self-assembled membrane, its preparation method, and its applications. This heterogeneous polyelectrolyte self-assembled membrane is formed by the self-assembly of polyelectrolytes with opposite charges. By applying this heterogeneous polyelectrolyte self-assembled membrane to aqueous flow batteries, this invention effectively suppresses capacity decay caused by the cross-mixing of redox active molecules through the membrane, thereby improving the battery's electrochemical performance. This heterogeneous polyelectrolyte self-assembled membrane provides a new strategy for improving the cycle stability of aqueous flow battery systems. The aqueous flow battery with ultra-long cycle stability involved in this invention has significant application value in the field of electrochemical energy storage devices.

[0007] The objective of this invention can be achieved through the following technical solutions:

[0008] A method for preparing a heterogeneous polyelectrolyte self-assembled membrane involves the self-assembly of the membrane into a flow battery separator on a central substrate during the flow of electrolytes on both sides of the flow battery, through strong electrostatic adsorption.

[0009] The electrolytes on both sides of the flow battery contain polyanionic complexes and polycationic complexes, respectively.

[0010] Furthermore, the polyanionic composite is sodium polystyrene sulfonate, the polycationic composite is polydiallyldimethylammonium chloride, and the substrate is a glass fiber substrate.

[0011] Furthermore, the specific preparation method of the heterogeneous polyelectrolyte self-assembled membrane is as follows:

[0012] S1. Preparation of electrolyte:

[0013] The polyanionic complex sodium polystyrene sulfonate and sodium chloride were dissolved in deionized water and used as the negative electrode electrolyte.

[0014] The polycationic complex polydiallyldimethylammonium chloride and sodium chloride were dissolved in deionized water and used as the positive electrode electrolyte.

[0015] S2. Constructing a flow battery:

[0016] The positive and negative electrolytes obtained in step S1 are added to the positive and negative electrode chambers of the external flow pump of the flow battery, respectively, with glass fiber as the separator substrate in between.

[0017] S3. Preparation of self-assembled membranes:

[0018] Turn on the flow pump of the flow battery built in step S2. During the circulation process, polyanions and polycations diffuse onto the glass fiber substrate and assemble into a heterogeneous polyelectrolyte self-assembled membrane under electrostatic interaction.

[0019] Furthermore, in step S1, the sodium polystyrene sulfonate has a molecular weight of 60,000-80,000 and a mass fraction of 1-10%.

[0020] The polydiallyl dimethyl ammonium chloride has a molecular weight of 200,000-350,000 and a mass fraction of 1-10%.

[0021] The concentration of sodium chloride is 1-3 mol / L.

[0022] Furthermore, in step S2, the glass fiber substrate is 1827-125 Whatman glass fiber.

[0023] Furthermore, in step S3, the flow rate of the flow pump is 20-60 mL / min, and the time is 10-40 min.

[0024] The present invention also provides a heterogeneous polyelectrolyte self-assembled membrane, wherein the heterogeneous polyelectrolyte self-assembled membrane prepared by the above preparation method comprises a glass fiber substrate and a polymer crosslinking network, wherein the polymer crosslinking network is formed by polymer chains of sodium polystyrene sulfonate and polydiallyl dimethyl ammonium chloride.

[0025] The present invention also provides an application of a heterogeneous polyelectrolyte self-assembled membrane in an aqueous flow battery.

[0026] The present invention also provides an aqueous flow battery, comprising an electrolyte in two electrode compartments and a heterogeneous polyelectrolyte self-assembled membrane located between the electrode compartments.

[0027] Furthermore, the electrodes inside the electrode compartment are carbon felt electrodes, and the thickness of the carbon felt electrodes is 2-4 mm;

[0028] The electrolyte is an electrolyte containing polyanionic complex and polycationic complex, and the volume of the electrolyte is 10-30 mL;

[0029] The heterogeneous polyelectrolyte self-assembled membrane is formed by the self-assembly of sodium polystyrene sulfonate and polydiallyl dimethyl ammonium chloride, and the thickness of the heterogeneous polyelectrolyte self-assembled membrane is 200 μm.

[0030] Furthermore, this invention also provides a method for preparing an aqueous flow battery, the specific steps of which are as follows:

[0031] (1) Turn on the flow pump of the flow battery and form a heterogeneous polyelectrolyte self-assembled membrane in situ on the glass fiber substrate during the circulation process.

[0032] (2) Subsequently, the redox active organic molecules of the negative electrode are added to the negative electrode electrolyte, and the redox active organic molecules of the positive electrode are added to the positive electrode electrolyte, finally obtaining an aqueous flow battery based on a heterogeneous polyelectrolyte self-assembled membrane.

[0033] Furthermore, the negative electrode redox active organic molecule is methyl viologen, and the concentration of methyl viologen is 0.1-0.5 mol / L;

[0034] The positive electrode redox active organic molecule is 4-hydroxy-2,2,6,6-tetramethylpiperidine nitroxide free radical, and the concentration of the 4-hydroxy-2,2,6,6-tetramethylpiperidine nitroxide free radical is 0.1-0.5 mol / L.

[0035] The principle of this invention is as follows:

[0036] In the flow battery electrolyte self-assembled membrane of this invention, during the flow of electrolyte, a polyanionic complex (sodium polystyrene sulfonate) in one side of the electrolyte and a polycationic complex (polydiallyldimethylammonium chloride) in the other side of the electrolyte self-assemble on a glass fiber substrate in the middle through strong electrostatic adsorption to form the separator of the flow battery. This heterogeneous polyelectrolyte self-assembled membrane not only possesses excellent mechanical properties (1.06-4.43 MPa) and ionic conductivity (44.8-65.9 mS / cm), but the microporous membrane structure formed can effectively inhibit the interpenetration and mixing of redox active molecules in the flow battery.

[0037] By matching this heterogeneous polyelectrolyte self-assembled membrane with typical redox-active organic molecules (methyl viologen and 4-hydroxy-2,2,6,6-tetramethylpiperidine nitroxide radical), an electrolyte and membrane system that maintains the long-term stability of aqueous flow batteries can be formed, retaining more than 97% of the initial capacity after 2000 charge-discharge cycles.

[0038] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0039] (1) The heterogeneous polyelectrolyte self-assembled membrane prepared by the present invention can effectively suppress the capacity decay caused by the permeation and cross-mixing of electrolyte redox active molecules through the membrane in aqueous flow batteries.

[0040] (2) The heterogeneous polyelectrolyte self-assembled membrane prepared by the present invention has excellent mechanical properties with MPa-level strength, which can effectively prevent the membrane from being punctured or torn, leading to rapid battery failure.

[0041] (3) The heterogeneous polyelectrolyte self-assembled membrane prepared by the present invention has extremely high ionic conductivity, which ensures the efficient operation of the electrochemical process;

[0042] (4) The formation of a stable electrolyte membrane system by heterogeneous polyelectrolytes and microporous self-assembled membranes provides a new strategy for improving the cycle stability of aqueous flow battery systems. Attached Figure Description

[0043] Figure 1 This is a schematic diagram of the synthesis of a heterogeneous polyelectrolyte self-assembled membrane involved in this invention;

[0044] Figure 2 This is a Zeta potential diagram of the heteropolymer polyelectrolyte self-assembled membrane in Example 1;

[0045] Figure 3 This is a scanning electron microscope image of the blank glass fiber substrate in Example 1;

[0046] Figure 4 This is a scanning electron microscope image of the sodium polystyrene sulfonate side of the self-assembled heteropolymer polymer electrolyte membrane in Example 1;

[0047] Figure 5 This is a scanning electron microscope image of the polydiallyldimethylammonium chloride side of the heterogeneous polymer electrolyte self-assembled membrane in Example 1;

[0048] Figure 6 This is a cross-sectional scanning electron microscope image of the self-assembled heteropolymer polymer electrolyte membrane in Example 1;

[0049] Figure 7 The image shows the pore size distribution of the heterogeneous polymer electrolyte self-assembled membranes prepared in Examples 1-4. psspda-X represents the self-assembled membrane, and X represents the weight ratio of the polyelectrolyte (X = 1, 2, 5, 10, in wt.%).

[0050] Figure 8 This is a comparison chart of the ionic conductivity of the heterogeneous polymer electrolyte self-assembled membranes prepared in Examples 1-4;

[0051] Figure 9 The tensile strength diagrams are of the heterogeneous polymer electrolyte self-assembled membranes prepared in Examples 1-4;

[0052] Figure 10 The rate performance of the aqueous flow battery in Example 5 under a self-assembled membrane system;

[0053] Figure 11 The cycling performance of the aqueous flow battery in Example 5 under a self-assembled membrane system;

[0054] Figure 12 This is a scanning electron microscope image of the self-assembled membrane of the aqueous flow battery in Example 5 after 2000 long cycles. Detailed Implementation

[0055] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. These embodiments are based on the technical solution of the present invention and provide detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0056] The following detailed description of some embodiments of the present invention is provided in conjunction with the accompanying drawings. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0057] Example 1

[0058] This embodiment provides a method for preparing a heterogeneous polyelectrolyte self-assembled membrane, the specific steps of which are as follows:

[0059] (1) Preparation of electrolyte:

[0060] 0.2 g of sodium polystyrene sulfonate and 0.02 mol of sodium chloride were dissolved in 20 mL of deionized water, and the resulting mixture was stirred vigorously at room temperature for 1 h to serve as the negative electrode electrolyte.

[0061] 0.2 g of polydiallyldimethylammonium chloride and 0.02 mol of sodium chloride were dissolved in 20 mL of deionized water. The resulting mixture was stirred vigorously at room temperature for 1 h and used as the positive electrode electrolyte.

[0062] (2) Constructing a flow battery:

[0063] The positive and negative electrolytes obtained in step (1) are added to the positive and negative electrode chambers of the flow pump connected to the flow battery, respectively, with a glass fiber substrate as a spacer in between.

[0064] (3) Preparation of self-assembled membranes:

[0065] Turn on the flow pump of the flow battery built in step (2), adjust the speed to 20 mL / min, and after circulating for 30 min, obtain a heterogeneous polymer electrolyte self-assembled membrane on the glass fiber substrate.

[0066] Figure 1 This is a schematic diagram of the synthesis of the heterogeneous polyelectrolyte self-assembled membrane involved in this embodiment; during the electrolyte flow process, the negatively charged sodium polystyrene sulfonate and the positively charged polydiallyldimethylammonium chloride meet on the glass fiber skeleton, and the strong electrostatic adsorption of the heterogeneous electrolyte forms a self-assembled membrane.

[0067] Figure 2 The image shows the zeta potential of the heteropolymer polyelectrolyte self-assembled membrane. The zeta potential indicates that charge balance has been achieved on the self-assembled membrane due to electrostatic adsorption, further demonstrating the tight bonding state of the heteropolymer polyelectrolyte self-assembled membrane.

[0068] Figure 3Scanning electron microscope image of a blank glass fiber substrate; Figure 4 Scanning electron microscope image of the sodium polystyrene sulfonate side of the self-assembled membrane; Figure 5 A scanning electron microscope image of one side of the self-assembled membrane, polydiallyldimethylammonium chloride. Figure 6 The image shows a cross-sectional scanning electron microscope (SEM) image of the self-assembled membrane. From the multi-position SEM images of the self-assembled membrane, it can be seen that the glass fiber provides the blank skeleton. Since the polymer chains of sodium polystyrene sulfonate and polydiallyl dimethyl ammonium chloride provide sufficient interconnecting elements, a dense polymer cross-linking network is formed. Therefore, a dense self-assembled membrane is formed at various locations, including the sodium polystyrene sulfonate side, the polydiallyl dimethyl ammonium chloride side, and the cross-section.

[0069] Example 2

[0070] This embodiment provides a method for preparing a heterogeneous polyelectrolyte self-assembled membrane, the specific steps of which are as follows:

[0071] (1) Preparation of electrolyte:

[0072] 0.4 g of sodium polystyrene sulfonate and 0.02 mol of sodium chloride were dissolved in 20 mL of deionized water. The resulting mixture was stirred vigorously at room temperature for 1 h and used as the negative electrode electrolyte.

[0073] 0.4 g of polydiallyldimethylammonium chloride and 0.02 mol of sodium chloride were dissolved in 20 mL of deionized water. The resulting mixture was stirred vigorously at room temperature for 1 h and used as the positive electrode electrolyte.

[0074] (2) Constructing a flow battery:

[0075] The positive and negative electrolytes obtained in step (1) are added to the positive and negative electrode chambers of the flow pump connected to the flow battery, respectively, with a glass fiber substrate as a spacer in between.

[0076] (3) Preparation of self-assembled membranes:

[0077] Turn on the flow pump of the flow battery built in step (2), adjust the speed to 20 mL / min, and after circulating for 30 min, obtain a heterogeneous polymer electrolyte self-assembled membrane on the glass fiber substrate.

[0078] Example 3

[0079] This embodiment provides a method for preparing a heterogeneous polyelectrolyte self-assembled membrane, the specific steps of which are as follows:

[0080] (1) Preparation of electrolyte:

[0081] 1 g of sodium polystyrene sulfonate and 0.02 mol of sodium chloride were dissolved in 20 mL of deionized water. The resulting mixture was stirred vigorously at room temperature for 1 h and used as the negative electrode electrolyte.

[0082] 1 g of polydiallyldimethylammonium chloride and 0.02 mol of sodium chloride were dissolved in 20 mL of deionized water. The resulting mixture was stirred vigorously at room temperature for 1 h and used as the positive electrode electrolyte.

[0083] (2) Constructing a flow battery:

[0084] The positive and negative electrolytes obtained in step (1) are added to the positive and negative electrode chambers of the flow pump connected to the flow battery, respectively, with a glass fiber substrate as a spacer in between.

[0085] (3) Preparation of self-assembled membranes:

[0086] Turn on the flow pump of the flow battery built in step (2), adjust the speed to 20 mL / min, and after circulating for 30 min, obtain a heterogeneous polymer electrolyte self-assembled membrane on the glass fiber substrate.

[0087] Example 4

[0088] This embodiment provides a method for preparing a heterogeneous polyelectrolyte self-assembled membrane, the specific steps of which are as follows:

[0089] (1) Preparation of electrolyte:

[0090] 2g of sodium polystyrene sulfonate and 0.02mol of sodium chloride were dissolved in 20mL of deionized water, and the resulting mixture was stirred vigorously at room temperature for 1h to serve as the negative electrode electrolyte.

[0091] 2g of polydiallyldimethylammonium chloride and 0.02mol of sodium chloride were dissolved in 20mL of deionized water, and the resulting mixture was stirred vigorously at room temperature for 1h to serve as the positive electrode electrolyte.

[0092] (2) Constructing a flow battery:

[0093] The positive and negative electrolytes obtained in step (1) are added to the positive and negative electrode chambers of the flow pump connected to the flow battery, respectively, with a glass fiber substrate as a spacer in between.

[0094] (3) Preparation of self-assembled membranes:

[0095] Turn on the flow pump of the flow battery built in step (2), adjust the speed to 20 mL / min, and after circulating for 30 min, obtain a heterogeneous polymer electrolyte self-assembled membrane on the glass fiber substrate.

[0096] Performance testing:

[0097] Figure 7 The image shows the pore size distribution of the heterogeneous polymer electrolyte self-assembled membranes prepared in Examples 1-4. psspda-X represents the self-assembled membrane, and X represents the weight ratio of the polyelectrolyte (X = 1, 2, 5, 10, in wt.%). It shows that the heterogeneous polyelectrolyte self-assembled membrane has a narrow distribution of sub-nanometer micropores. As the concentration of polyelectrolyte increases, the free volume elements in the membrane gradually become smaller and narrower, and the pore size also becomes smaller and smaller. This can provide reasonable size selectivity to avoid the cross-contamination of large redox active substances.

[0098] Figure 8 The graph shows a comparison of the ionic conductivity of the heterogeneous polymer electrolyte self-assembled membranes prepared in Examples 1-4. The introduction of polyelectrolytes improves the ionic conductivity and provides more ionic conductive groups, so that the conductivity of membranes with different proportions can be maintained at around 50 mS / cm at room temperature.

[0099] Figure 9 The tensile strength diagrams are shown for the heterogeneous polymer electrolyte self-assembled membranes prepared in Examples 1-4. It can be seen that the heterogeneous polyelectrolyte self-assembled membranes have excellent mechanical properties with strength in the MPa range, which can effectively prevent the membrane from being punctured or torn, thus preventing the battery from failing rapidly and making it more conducive to the stable operation of aqueous flow batteries.

[0100] Example 5

[0101] This embodiment provides an application of a heterogeneous polyelectrolyte self-assembled membrane in an aqueous flow battery. The specific preparation method of the aqueous flow battery is as follows:

[0102] (1) Preparation of electrolyte:

[0103] 0.4 g of sodium polystyrene sulfonate and 0.04 mol of sodium chloride were dissolved in 20 mL of deionized water, and the resulting mixture was stirred vigorously at room temperature for 1 h to serve as the negative electrode electrolyte.

[0104] 0.4 g of polydiallyldimethylammonium chloride and 0.04 mol of sodium chloride were dissolved in 20 mL of deionized water. The resulting mixture was stirred vigorously at room temperature for 1 h and used as the positive electrode electrolyte.

[0105] (2) Constructing a flow battery:

[0106] The positive and negative electrolytes obtained in step (1) are added to the positive and negative electrode chambers of the flow pump connected to the flow battery, respectively, with a glass fiber substrate as a spacer in between.

[0107] (3) Preparation of self-assembled membranes:

[0108] Turn on the flow pump of the flow battery built in step (2), adjust the speed to 20 mL / min, and after circulating for 30 min, obtain a heterogeneous polyelectrolyte self-assembled membrane on the glass fiber substrate.

[0109] (4) Subsequently, the negative electrode redox active organic molecule (0.004 mol methyl viologen) was added to the negative electrode electrolyte and stirred for 1 h; the positive electrode redox active organic molecule (0.004 mol 4-hydroxy-2,2,6,6-tetramethylpiperidine nitric oxide radical) was added to the positive electrode electrolyte and stirred for 1 h, finally obtaining an aqueous flow battery based on a heterogeneous polyelectrolyte self-assembled membrane;

[0110] Figure 10 The graph shows the rate performance of an aqueous flow battery in a self-assembled membrane system; at constant current densities of 40, 60, 80, and 100 mA / cm². 2 The system exhibited high coulombic efficiency at all rate levels, and its capacity could be fully restored to the original level after cycling at different rates, verifying the excellent stability of the aqueous flow battery system.

[0111] Figure 11 The graph shows the cycling performance of an aqueous flow battery in a self-assembled membrane system; at 80 mA / cm². 2 After 2000 cycles at a current density, the capacity is still able to maintain 97.15% of the initial capacity.

[0112] Figure 12 This is a scanning electron microscope (SEM) image of the self-assembled membrane of an aqueous flow battery after 2000 charge-discharge cycles. It can be seen that the membrane morphology remains very intact after 2000 charge-discharge cycles.

[0113] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A method for preparing a heterogeneous polyelectrolyte self-assembled membrane, characterized in that, During the flow of electrolytes on both sides of the flow battery, they self-assemble on the intermediate substrate through strong electrostatic adsorption to form the flow battery's separator, namely a heterogeneous polyelectrolyte self-assembled membrane. The electrolytes on both sides of the flow battery contain polyanionic complexes and polycationic complexes, respectively. The polyanionic complex is sodium polystyrene sulfonate, the polycationic complex is polydiallyldimethylammonium chloride, and the substrate is a glass fiber substrate. The specific preparation method of the heterogeneous polyelectrolyte self-assembled membrane is as follows: S1. Preparation of electrolyte: The polyanionic complex sodium polystyrene sulfonate and sodium chloride were dissolved in deionized water and used as the negative electrode electrolyte. The polycationic complex polydiallyldimethylammonium chloride and sodium chloride were dissolved in deionized water and used as the positive electrode electrolyte. S2. Constructing a flow battery: The positive and negative electrolytes obtained in step S1 are added to the positive and negative electrode chambers of the external flow pump of the flow battery, respectively, with glass fiber as the separator substrate in between. S3. Preparation of self-assembled membranes: Turn on the flow pump of the flow battery built in step S2. During the circulation process, polyanions and polycations diffuse onto the glass fiber substrate and assemble into a heterogeneous polyelectrolyte self-assembled membrane under electrostatic interaction.

2. The method for preparing a heterogeneous polyelectrolyte self-assembled membrane according to claim 1, characterized in that, In step S1, the sodium polystyrene sulfonate has a molecular weight of 60,000-80,000 and a mass fraction of 1-10%. The polydiallyl dimethyl ammonium chloride has a molecular weight of 200,000-350,000 and a mass fraction of 1-10%. The concentration of sodium chloride is 1-3 mol / L.

3. The method for preparing a heterogeneous polyelectrolyte self-assembled membrane according to claim 1, characterized in that, In step S3, the flow rate of the flow pump is 20-60 mL / min, and the time is 10-40 min.

4. A heterogeneous polyelectrolyte self-assembled membrane, characterized in that, The heterogeneous polyelectrolyte self-assembled membrane prepared by any of the preparation methods described in claims 1-3 comprises a glass fiber substrate and a polymer crosslinking network, wherein the polymer crosslinking network is formed by polymer chains of sodium polystyrene sulfonate and polydiallyl dimethyl ammonium chloride.

5. The application of a heterogeneous polyelectrolyte self-assembled membrane as described in claim 4 in an aqueous flow battery.

6. An aqueous flow battery, characterized in that, It includes an electrolyte in two electrode chambers and a heterogeneous polyelectrolyte self-assembled membrane as described in claim 4, located between the electrode chambers.

7. The aqueous flow battery according to claim 6, characterized in that, The electrodes inside the electrode compartment are carbon felt electrodes, and the thickness of the carbon felt electrodes is 2-4 mm; The electrolyte is an electrolyte containing polyanionic complex and polycationic complex, and the volume of the electrolyte is 10-30 mL; The heterogeneous polyelectrolyte self-assembled membrane is formed by the self-assembly of sodium polystyrene sulfonate and polydiallyl dimethyl ammonium chloride, and the thickness of the heterogeneous polyelectrolyte self-assembled membrane is 200 μm.

8. A method for preparing an aqueous flow battery as described in claim 6 or claim 7, characterized in that, The specific steps are as follows: (1) Turn on the flow pump of the flow battery and form a heterogeneous polyelectrolyte self-assembled membrane in situ on the glass fiber substrate during the circulation process; (2) Subsequently, the redox active organic molecules of the negative electrode are added to the negative electrode electrolyte, and the redox active organic molecules of the positive electrode are added to the positive electrode electrolyte, and finally an aqueous flow battery based on a heterogeneous polyelectrolyte self-assembled membrane is obtained.

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