Heterogeneous polyelectrolyte self-assembled membrane as well as preparation method and application thereof

Abstract

The invention relates to a heterogeneous polyelectrolyte self-assembled membrane as well as a preparation method and application thereof. In the flowing process of the electrolyte of the flow battery, the polyanion compound in the electrolyte on one side and the polycation compound in the electrolyte on the other side are self-assembled on the glass fiber substrate in the middle under the action of strong electrostatic adsorption to form the diaphragm of the flow battery, namely the heterogeneous polyelectrolyte self-assembled membrane. The microporous membrane has good mechanical properties and ionic conductivity, and the formed microporous membrane structure can effectively inhibit interpenetration and mixing of redox active molecules in the flow battery. The aqueous flow battery system assembled by the heterogeneous polyelectrolyte self-assembled membrane and typical oxidation-reduction active organic molecules still keeps the initial capacity of 97% or above after 2000 charge-discharge cycles. Compared with the prior art, the heterogeneous polyelectrolyte self-assembled membrane provided by the invention can effectively inhibit capacity attenuation caused by permeation and cross mixing of electrolyte redox active molecules in an aqueous flow battery through the membrane.

Description

Technical Field

[0001] The present invention relates to the technical field of electrochemical energy storage, and in particular to a heterogeneous polyelectrolyte self-assembled membrane and a preparation method and application thereof. Background Art

[0002] Aqueous flow batteries have shown great application prospects in the field of energy storage due to their safety, environmental friendliness and scalability. Aqueous flow batteries use water as the electrolyte solvent, which is non-flammable and low-toxic. At the same time, they avoid the use of organic solvents and transition metals, reducing environmental pollution. The energy and power of aqueous flow batteries can be independently designed, 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 metal substances has been widely studied and reported. Although redox active substances show good electrochemical reversibility in aqueous flow batteries, the cycle stability is still limited by the diaphragm. The penetration and cross-mixing of redox active molecules through the diaphragm leads to battery capacity decay, which is a key factor affecting the cycle stability of flow batteries.

[0004] The diaphragm in the aqueous flow battery must not only achieve efficient transmission of charged ions, but also prevent cross-penetration and mixing of redox-active molecules. Therefore, a trade-off needs to be made between a series of properties such as ionic conductivity, selective permeability, and mechanical stability to achieve high-capacity, long-life aqueous flow batteries. High ionic conductivity usually requires larger pore sizes and higher porosity, but this increases the risk of penetration of redox-active molecules. The diaphragm needs to have sufficient mechanical strength to withstand the physical and chemical stresses of long-term operation. The diaphragm material needs to have good chemical compatibility with the electrolyte and redox-active molecules to avoid degradation or performance degradation.

[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 there are still problems such as complex membrane preparation process and high cost. The compatibility of electrolyte / membrane system and redox-active molecules also needs to be solved urgently. Summary of the invention

[0006] The purpose of the present invention is to provide a heterogeneous polyelectrolyte self-assembled membrane and its preparation method and application in order to overcome the defects of the above-mentioned prior art. The heterogeneous polyelectrolyte self-assembled membrane is formed by self-assembly of polyelectrolytes with opposite charges. The present invention applies the heterogeneous polyelectrolyte self-assembled membrane to an aqueous liquid flow battery, thereby effectively inhibiting the capacity decay caused by the permeation cross-mixing of redox-active molecules through the membrane, so as to improve the electrochemical performance of the battery. This heterogeneous polyelectrolyte self-assembled membrane provides a new strategy for improving the cycle stability of the aqueous liquid flow battery system. The aqueous liquid flow battery with ultra-long cycle stability involved in the present invention has great application value in the field of electrochemical energy storage devices.

[0007] The purpose of the present invention can be achieved by the following technical solutions:

[0008] A method for preparing a heterogeneous polyelectrolyte self-assembled membrane, in which, during the flow of electrolytes on both sides of a flow battery, the membrane is self-assembled on a substrate in the middle through strong electrostatic adsorption to form a membrane of the flow battery, namely, a heterogeneous polyelectrolyte self-assembled membrane.

[0009] The electrolytes at both sides of the liquid flow battery contain polyanion complexes and polycation complexes respectively.

[0010] Furthermore, the polyanion complex is sodium polystyrene sulfonate, the polycation complex 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. Prepare electrolyte:

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

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

[0015] S2. Build a flow battery:

[0016] The positive electrode electrolyte and the negative electrode electrolyte obtained in step S1 are respectively added to the positive and negative electrode compartments of the external flow pump of the flow battery, and glass fiber is used as a diaphragm substrate in the middle;

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

[0018] The flow pump of the flow battery constructed in step S2 is turned on. During the circulation process, the polyanions and polycations diffuse onto the glass fiber substrate respectively and assemble to form a heterogeneous polyelectrolyte self-assembled film under electrostatic interaction.

[0019] Furthermore, in step S1, the molecular weight of the sodium polystyrene sulfonate is 60000-80000, and the mass fraction of the sodium polystyrene sulfonate is 1-10%.

[0020] The molecular weight of the polydiallyldimethylammonium chloride is 200000-350000, and the mass fraction of the polydiallyldimethylammonium chloride is 1-10%.

[0021] The concentration of the 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. The heterogeneous polyelectrolyte self-assembled membrane prepared by the preparation method comprises a glass fiber substrate and a polymer cross-linked network, wherein the polymer cross-linked network is formed by sodium polystyrene sulfonate and polydiallyldimethylammonium chloride polymer chains.

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

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

[0027] Furthermore, the electrode in the electrode compartment is a carbon felt electrode, and the thickness of the carbon felt electrode is 2-4 mm;

[0028] The electrolyte is an electrolyte containing a polyanion complex and a polycation complex, and the volume of the electrolyte is 10-30 mL;

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

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

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

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

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

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

[0035] The principle of the present invention is as follows:

[0036] During the flow of electrolyte in a flow battery, the polyanion complex (sodium polystyrene sulfonate) in one side of the electrolyte and the polycation complex (polydiallyldimethylammonium chloride) in the other side of the electrolyte are self-assembled on the glass fiber substrate in the middle through strong electrostatic adsorption to form a diaphragm of the flow battery. The heterogeneous polyelectrolyte self-assembled membrane not only has good mechanical properties (1.06-4.43MPa) and ionic conductivity (44.8-65.9mS / cm), but also has a microporous membrane structure that can effectively inhibit the mutual penetration and mixing of redox active molecules in the flow battery.

[0037] Matching this heterogeneous polyelectrolyte self-assembled membrane with typical redox-active organic molecules (methyl viologen and 4-hydroxy-2,2,6,6-tetramethylpiperidinyl nitroxide free radical) can form an electrolyte and diaphragm system that maintains the long-term stability of aqueous liquid flow batteries, and still maintains more than 97% of the initial capacity after 2000 charge and 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 inhibit the capacity decay caused by the penetration and cross-mixing of electrolyte redox active molecules through the membrane in aqueous liquid 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, resulting in rapid failure of the battery;

[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 heterogeneous polyelectrolyte and microporous self-assembled membrane form a stable electrolyte membrane system, which provides a new strategy to improve the cyclic stability of aqueous liquid flow battery systems. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 A schematic diagram of the synthesis of the heterogeneous polyelectrolyte self-assembled membrane involved in the present invention;

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

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

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

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

[0048] Figure 6 is a cross-sectional scanning electron micrograph of the heterogeneous polymer electrolyte self-assembled membrane in Example 1;

[0049] Figure 7 The pore size distribution diagram of the heterogeneous polymer electrolyte self-assembled membranes prepared in Examples 1 to 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 is a comparison chart of ionic conductivities of the heterogeneous polymer electrolyte self-assembled membranes prepared in Examples 1 to 4;

[0051] Fig. 9 is a graph showing the tensile strength of the heterogeneous polymer electrolyte self-assembled films prepared in Examples 1 to 4;

[0052] Fig.10 The rate performance of the aqueous liquid flow battery in the self-assembled membrane system in Example 5;

[0053] Fig.11 The cycle performance of the aqueous liquid flow battery in the self-assembled membrane system in Example 5;

[0054] Fig.12 This is a scanning electron microscopy image of the self-assembled membrane of the aqueous liquid flow battery in Example 5 after 2000 long cycles. DETAILED DESCRIPTION

[0055] The present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0056] In conjunction with the accompanying drawings, some embodiments of the present invention are described in detail below. In the absence of conflict, the following embodiments and features in the embodiments may be combined with each other.

[0057] Example 1

[0058] This embodiment provides a method for preparing a heterogeneous polyelectrolyte self-assembled membrane, and the specific steps 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 vigorously stirred at room temperature for 1 h 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, and the resulting mixture was vigorously stirred at room temperature for 1 h as the positive electrode electrolyte.

[0062] (2) Building a flow battery:

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

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

[0065] The flow pump of the flow battery constructed in step (2) was turned on, and the speed was adjusted to 20 mL / min. After circulating for 30 minutes, a heterogeneous polymer electrolyte self-assembled membrane was obtained on the glass fiber substrate.

[0066] Figure 1 Schematic diagram of the synthesis of the heterogeneous polyelectrolyte self-assembled membrane involved in this embodiment; during the flow of electrolyte, negatively charged sodium polystyrene sulfonate and 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 This is the Zeta potential diagram of the heterogeneous polyelectrolyte self-assembled film; the Zeta potential shows that due to electrostatic adsorption, charge balance is achieved on the self-assembled film, which further proves the tightly bound state of the heterogeneous polyelectrolyte self-assembled film.

[0068] Figure 3is the SEM image of the blank glass fiber substrate; Figure 4 This is a scanning electron micrograph of the sodium polystyrene sulfonate side of the self-assembled membrane; Figure 5 This is a scanning electron micrograph of one side of the self-assembled film of polydiallyldimethylammonium chloride; Figure 6 This is a cross-sectional scanning electron microscope image of the self-assembled film; from the multi-position scanning electron microscope images of the self-assembled film, it can be seen that the glass fiber provides a blank skeleton, and since the sodium polystyrene sulfonate and polydiallyldimethylammonium chloride polymer chains provide sufficient interconnecting elements to form a dense polymer cross-linked network, a dense self-assembled film is formed at various positions such as the sodium polystyrene sulfonate side, the polydiallyldimethylammonium chloride side and the cross section.

[0069] Example 2

[0070] This embodiment provides a method for preparing a heterogeneous polyelectrolyte self-assembled membrane, and the specific steps 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, and the resulting mixture was vigorously stirred at room temperature for 1 h 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, and the resulting mixture was vigorously stirred at room temperature for 1 h as the positive electrode electrolyte.

[0074] (2) Building a flow battery:

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

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

[0077] The flow pump of the flow battery constructed in step (2) was turned on, and the speed was adjusted to 20 mL / min. After circulating for 30 minutes, a heterogeneous polymer electrolyte self-assembled membrane was obtained on the glass fiber substrate.

[0078] Example 3

[0079] This embodiment provides a method for preparing a heterogeneous polyelectrolyte self-assembled membrane, and the specific steps 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, and the resulting mixture was vigorously stirred at room temperature for 1 h 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, and the resulting mixture was vigorously stirred at room temperature for 1 h as the positive electrode electrolyte.

[0083] (2) Building a flow battery:

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

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

[0086] The flow pump of the flow battery constructed in step (2) was turned on, and the speed was adjusted to 20 mL / min. After circulating for 30 minutes, a heterogeneous polymer electrolyte self-assembled membrane was obtained on the glass fiber substrate.

[0087] Example 4

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

[0089] (1) Preparation of electrolyte:

[0090] 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 vigorously stirred at room temperature for 1 h as the negative electrode electrolyte;

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

[0092] (2) Building a flow battery:

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

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

[0095] The flow pump of the flow battery constructed in step (2) was turned on, and the speed was adjusted to 20 mL / min. After circulating for 30 minutes, a heterogeneous polymer electrolyte self-assembled membrane was obtained on the glass fiber substrate.

[0096] Performance Testing:

[0097] Figure 7 The pore size distribution diagram of the heterogeneous polymer electrolyte self-assembled membrane prepared in Examples 1 to 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 subnanometer micropores. As the concentration of the polyelectrolyte increases, the free volume elements in the membrane gradually become smaller and narrower, and the pore size also becomes smaller and smaller, which can provide reasonable size selectivity to avoid the intersection of larger redox active substances.

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

[0099] Fig. 9 Graph showing the tensile strength of the heterogeneous polymer electrolyte self-assembled membranes prepared in Examples 1 to 4; it can be seen that the heterogeneous polyelectrolyte self-assembled membranes have excellent mechanical properties with MPa-level strength, which can effectively prevent the membrane from being punctured or torn, resulting in rapid battery failure, and is more conducive to the stable operation of the aqueous liquid flow battery.

[0100] Example 5

[0101] This embodiment provides an application of a heterogeneous polyelectrolyte self-assembled membrane in an aqueous liquid flow battery. The specific preparation method of the aqueous liquid 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 vigorously stirred at room temperature for 1 h 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, and the resulting mixture was vigorously stirred at room temperature for 1 h as the positive electrode electrolyte.

[0105] (2) Building a flow battery:

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

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

[0108] The flow pump of the flow battery constructed in step (2) was turned on, and the speed was adjusted to 20 mL / min. After circulating for 30 min, a heterogeneous polyelectrolyte self-assembled membrane was obtained on the glass fiber substrate;

[0109] (4) Then, the negative electrode redox active organic molecule (0.004 mol methyl viologen) was added to the negative electrode electrolyte and stirred for 1 hour; the positive electrode redox active organic molecule (0.004 mol 4-hydroxy-2,2,6,6-tetramethylpiperidinyl nitroxide free radical) was added to the positive electrode electrolyte and stirred for 1 hour, and finally an aqueous liquid flow battery based on heterogeneous polyelectrolyte self-assembled membrane was obtained;

[0110] Fig.10 This is the rate performance diagram of aqueous flow battery in self-assembled membrane system; at constant current density of 40, 60, 80 and 100 mA / cm 2 The rate performance at all times showed a high Coulombic efficiency, and the capacity could be fully restored to its original level after cycling at different rates, verifying the excellent stability of the aqueous flow battery system.

[0111] Fig.11 This is the cycling performance diagram of aqueous flow battery in self-assembled membrane system; at 80mA / cm 2 After 2000 cycles at a current density of , the capacity can still be maintained at 97.15% of the initial capacity.

[0112] Fig.12 This is a scanning electron microscope image of the self-assembled membrane of the aqueous flow battery after 2000 long cycles. It can be seen that after 2000 charge and discharge cycles, the morphology of the membrane is still intact.

[0113] The above description of the embodiments is to facilitate the understanding and use of the invention by those skilled in the art. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative work. Therefore, the present invention is not limited to the above embodiments, and 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 present invention should be within the scope of protection of the present invention.

Claims

1. A method for preparing a heterogeneous polyelectrolyte self-assembled membrane, characterized in that: During the flow of electrolyte on both sides of the flow battery, the electrolyte self-assembles on the substrate in the middle through strong electrostatic adsorption to form the diaphragm of the flow battery, that is, the heterogeneous polyelectrolyte self-assembled membrane. The electrolytes at both sides of the liquid flow battery contain polyanion complexes and polycation complexes respectively.

2. The method for preparing a heterogeneous polyelectrolyte self-assembled membrane according to claim 1, characterized in that: The polyanion complex is sodium polystyrene sulfonate, the polycation complex is polydiallyldimethylammonium chloride, and the substrate is a glass fiber substrate.

3. The method for preparing a heterogeneous polyelectrolyte self-assembled membrane according to claim 2, characterized in that: The specific preparation method of the heterogeneous polyelectrolyte self-assembled membrane is as follows: S1. Prepare electrolyte: The polyanion complex sodium polystyrene sulfonate and sodium chloride were dissolved in deionized water as the negative electrode electrolyte. The polycationic complex polydiallyldimethylammonium chloride and sodium chloride were dissolved in deionized water to serve as the positive electrode electrolyte; S2. Build a flow battery: The positive electrode electrolyte and the negative electrode electrolyte obtained in step S1 are respectively added to the positive and negative electrode compartments of the external flow pump of the flow battery, and glass fiber is used as a diaphragm substrate in the middle; S3. Preparation of self-assembled membrane: The flow pump of the flow battery constructed in step S2 is turned on. During the circulation process, the polyanions and polycations diffuse onto the glass fiber substrate respectively and assemble to form a heterogeneous polyelectrolyte self-assembled film under electrostatic interaction.

4. The method for preparing a heterogeneous polyelectrolyte self-assembled membrane according to claim 3, characterized in that: In step S1, the molecular weight of the sodium polystyrene sulfonate is 60000-80000, and the mass fraction of the sodium polystyrene sulfonate is 1-10%. The molecular weight of the polydiallyldimethylammonium chloride is 200000-350000, and the mass fraction of the polydiallyldimethylammonium chloride is 1-10%. The concentration of the sodium chloride is 1-3 mol / L.

5. The method for preparing a heterogeneous polyelectrolyte self-assembled membrane according to claim 3, characterized in that: In step S2, the glass fiber substrate is 1827-125 whatman glass fiber; In step S3, the flow pump has a flow rate of 20-60 mL / min and a time of 10-40 min.

6. A heterogeneous polyelectrolyte self-assembled membrane, characterized in that: The heterogeneous polyelectrolyte self-assembled membrane prepared by the preparation method described in any one of claims 1 to 5 comprises a glass fiber substrate and a polymer cross-linked network, wherein the polymer cross-linked network is formed by sodium polystyrene sulfonate and polydiallyldimethylammonium chloride polymer chains.

7. Application of a heterogeneous polyelectrolyte self-assembled membrane in aqueous liquid flow batteries.

8. An aqueous liquid flow battery, characterized in that: It includes electrolyte in electrode compartments on both sides and a heterogeneous polyelectrolyte self-assembled membrane located between the electrode compartments.

9. An aqueous liquid flow battery according to claim 8, characterized in that: The electrode in the electrode compartment is a carbon felt electrode, and the thickness of the carbon felt electrode is 2-4 mm; The electrolyte is an electrolyte containing a polyanion complex and a polycation complex, and the volume of the electrolyte is 10-30 mL; The heterogeneous polyelectrolyte self-assembled film is formed by self-assembly of sodium polystyrene sulfonate and polydiallyldimethylammonium chloride, and the thickness of the heterogeneous polyelectrolyte self-assembled film is 200 μm.

10. A method for preparing an aqueous liquid flow battery according to claim 8 or claim 9, characterized in that: The specific steps are as follows: (1) turning on the flow pump of the flow battery to form a heterogeneous polyelectrolyte self-assembled membrane in situ on the glass fiber substrate during the circulation process; (2) Then, the negative electrode redox active organic molecules are added to the negative electrode electrolyte, and the positive electrode redox active organic molecules are added to the positive electrode electrolyte, and finally an aqueous liquid flow battery based on heterogeneous polyelectrolyte self-assembled membrane is obtained.

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