Electrolyte containing polyanionic electrolyte additive and flow battery

Abstract

The invention belongs to the technical field of flow batteries, and relates to an electrolyte containing a polyanionic electrolyte additive and a flow battery. Comprising a viologen compound, a supporting electrolyte, a solvent and a polyanionic electrolyte additive, the polyanionic electrolyte additive accounts for 0.1%-20% of the electrolyte in percentage by mass; molecules of the polyanionic electrolyte additive are rich in various functional groups with negative charges, and the polyanionic electrolyte additive is used for interfering the pi-pi accumulation behavior of viologen molecules; the polyanionic electrolyte additive is a polymer containing a repetitive unit, and is sodium polystyrenesulfonate, sodium polyacrylate, poly (2-acrylamido-2-methyl sodium propanesulfonate) or sodium alginate. By introducing a polymer carrying high-density negative charges in the structure or aggregated inorganic anions, multiple regulation and control effects on viologen molecules in a water-phase environment are realized, aggregation behaviors of reduced molecules of the viologen molecules are remarkably inhibited, and chemical and electrochemical stability of the electrolyte is improved.

Description

Technical Field

[0001] This invention belongs to the field of flow battery technology, specifically relating to an electrolyte containing polyanionic electrolyte additives and a flow battery. Background Technology

[0002] Flow batteries are an electrochemical energy storage technology with high safety, long cycle life, and stable output performance. Due to their unique structure where the electrolyte is separated from the battery stack, they are widely used in large-scale renewable energy integration, grid peak shaving, and frequency regulation. Among them, aqueous organic flow batteries, which use designable and synthesizable organic molecules as electrolyte active materials, have advantages such as tunable molecular structure, abundant raw material sources, environmental friendliness, and controllable costs, making them a promising next-generation flow battery system.

[0003] Viologen compounds have been widely studied and applied in aqueous organic flow batteries due to their good redox reversibility, fast electron transfer rate, and moderate electrochemical stability window. However, viologen molecules readily undergo strong π-π stacking interactions in aqueous solutions, especially in their one-electron reduced state (V0). + • It is more likely to form aggregates or deposits through interfacial stacking, resulting in a decrease in the utilization rate of active materials, a deterioration in electrolyte stability, and a rapid decay of battery capacity, thereby limiting its lifespan and reliability in practical applications.

[0004] Currently, to address the issue of viologen molecules' tendency to aggregate in aqueous solutions, some studies have attempted to use molecular structure modification strategies, such as introducing larger substituents, long-chain groups, or charge-controlled structures, to increase steric hindrance or charge repulsion between molecules, thereby inhibiting aggregation behavior. While these methods have improved the solubility and cycling stability of viologen molecules to some extent, their complex molecular design and high synthesis costs hinder large-scale industrial applications. Summary of the Invention

[0005] The purpose of this invention is to provide an electrolyte and flow battery containing a polyanionic electrolyte additive. By introducing polymers or aggregated inorganic anions carrying high-density negative charges into the structure, multiple regulatory effects on viologen molecules are achieved in an aqueous environment, significantly inhibiting the aggregation behavior of their reduced molecules and improving the chemical and electrochemical stability of the electrolyte.

[0006] This invention is achieved through the following technical solution: This invention discloses an electrolyte containing a polyanionic electrolyte additive, comprising viologen compound, supporting electrolyte, solvent and polyanionic electrolyte additive; By mass percentage, polyanionic electrolyte additives account for 0.1% to 20% of the electrolyte; The polyanionic electrolyte additive is rich in a variety of negatively charged functional groups, which are used to interfere with the π-π stacking behavior of viologen molecules. The polyanionic electrolyte additive is a polymer containing repeating units.

[0007] Furthermore, the polymer containing repeating units is sodium polystyrene sulfonate, sodium polyacrylate, poly(2-acrylamido-2-methylpropanesulfonate) or sodium alginate.

[0008] Furthermore, the viologen compound is a viologen derivative with various structural types, including one or more of the following: alkyl-substituted viologen, quaternary ammonium cation-modified viologen, sulfonate-modified viologen, phosphate-modified viologen, carboxylic acid hydroxyl-modified viologen, and hydroxyl-modified viologen.

[0009] Furthermore, the supporting electrolyte includes one or more of alkali metal chlorides, alkaline earth metal chlorides, alkali metal sulfates, alkaline earth metal sulfates, alkali metal phosphates, alkaline earth metal phosphates, alkali metal sulfonates, and alkaline earth metal sulfonates.

[0010] Furthermore, the pH value of the electrolyte is in the range of 3 to 10.

[0011] Furthermore, the solvent is an aqueous solvent.

[0012] Furthermore, the aqueous solvent is deionized water, heavy water, or a buffer solution.

[0013] Furthermore, the electrolyte is suitable for redox flow battery systems.

[0014] The present invention also discloses a flow battery, comprising a positive electrode electrolyte, a negative electrode electrolyte, and a separator separating the two, wherein the negative electrode electrolyte is the electrolyte containing polyanionic electrolyte additives.

[0015] Compared with the prior art, the present invention has the following beneficial technical effects: This invention provides an electrolyte containing a polyanionic electrolyte additive, which exhibits the following synergistic mechanisms in solution: Electrostatic adsorption and charge shielding: Viologen molecules in aqueous solution typically exist as divalent cations or free radical cations (V... 2+ / V +• Existing in the form of polyanionic molecules, these molecules are prone to aggregation during battery operation. The polyanionic molecules introduced in this invention can electrostatically adsorb onto the positively charged sites of viologen molecules in solution. By forming dynamic coordination or electrostatic association structures, a charged shell is built around the viologen molecules, reducing the probability of direct contact between molecules and thus effectively disrupting the formation conditions of their face-to-face π-π stacking conformation.

[0016] Multi-point binding and enhanced intermolecular repulsion: Compared to traditional single-point coordination or low-molecular-weight anions, the polyanions used in this invention, due to their long molecular chains and high structural flexibility, can simultaneously engage in multi-point electrostatic or hydrogen bonding interactions with multiple viologen molecules. This "dispersed coating" or "chain adsorption" method significantly improves the dispersibility of viologen in the electrolyte, while enhancing the electrostatic repulsion between different viologen molecules and blocking the thermodynamic drive for their tendency to aggregate into sheets.

[0017] Steric hindrance and hydration: The polyanion itself has a large structure and easily forms a highly hydrated shell in water. Its space occupation and hydration encapsulation effect further physically prevent the close stacking of viologen molecules. At the same time, the hydrated polyanion can increase the overall solvation degree of the system, which is conducive to the stable existence and diffusion of free radical intermediates and slows down the precipitation or activity loss caused by self-polymerization.

[0018] Through the above synergistic mechanism, this polyanionic additive effectively improves the stability of viologen in the electrolyte without altering its molecular structure, significantly alleviating the capacity decay problem during cycling. Compared with traditional molecular chemical modification methods, this invention is simpler to operate, has a shorter synthesis route, and uses a wide range of raw materials, possessing significant advantages such as low cost and suitability for large-scale formulation and industrial application. Attached Figure Description

[0019] Figure 1 The results of cyclic voltammetry tests of the methyl viologen electrolyte without the addition of PSS-Na in Example 1 of this invention; Figure 2 The results of cyclic voltammetry tests of the methyl viologen electrolyte with PSS-Na added in Example 1 of this invention; Figure 3 The MVCl2 / 4-(NMe3) assembled in Example 2 of this invention + Charge-discharge curves of TEMPO batteries; Figure 4 The MVCl2 / 4-(NMe3) assembled in Example 2 of this invention + - Capacity-coulomb efficiency plot of TEMPO battery over long cycle.

[0020] Figure 5 The MVCl2 / 4-(NMe3) assembled in Example 2 of this invention with added PSS-Na additive + Charge-discharge curves of TEMPO batteries; Figure 6 The MVCl2 / 4-(NMe3) assembled in Example 2 of this invention with added PSS-Na additive + - Capacity-coulomb efficiency plot of TEMPO battery over long cycle. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of the present invention clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention; that is, the described embodiments are only a part of the embodiments of the present invention, and not all of them.

[0022] The detailed description of the embodiments of the present invention provided in the following figures is not intended to limit the scope of the claimed invention, but merely to illustrate one selected embodiment of the invention. All other embodiments obtained by those skilled in the art based on the figures and embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0023] This invention discloses an electrolyte containing a polyanionic electrolyte additive, comprising the following core components: viologen compound, supporting electrolyte, solvent, and the key polyanionic electrolyte additive. The polyanionic electrolyte additive comprises 0.1% to 20% by mass of the total electrolyte mass. This additive is a polymer with repeating units in its molecular structure, and its molecular chain is rich in various negatively charged functional groups, such as sulfonic acid groups and carboxylic acid groups. These densely packed negatively charged groups can effectively interfere with and inhibit the π-π stacking behavior between viologen molecules due to the π-electron system through electrostatic interactions and steric hindrance effects in the electrolyte, thereby improving the stability and electrochemical performance of the electrolyte.

[0024] The polyanionic additive binds to viologen molecules (such as Vi) in the aqueous phase via electrostatic adsorption. 2+ Or Vi + This forms a non-covalent association structure, weakening the electrostatic attraction and π–π stacking tendency between viologen molecules, thereby effectively preventing their aggregation and precipitation, and improving their solubility and stability in water.

[0025] The polymer chains of the polyanionic structure can also provide steric hindrance, building a physical isolation barrier between viologen molecules and further reducing the probability of their close-range interaction; at the same time, its hydrated shell enhances the solvation capability of the entire electrolyte system and improves the stability of viologen radicals in the electrolyte.

[0026] The polyanionic additive is a water-soluble material that can be stably dissolved in an aqueous electrolyte system. It will not precipitate at high concentrations, nor will it significantly reduce the conductivity or diffusion performance of the electrolyte.

[0027] The polymer containing repeating units is specifically selected from one or more of the following polyanionic substances: sodium polystyrene sulfonate (PSS-Na), sodium polyacrylate (PAAS), poly(2-acrylamido-2-methylpropanesulfonate) (PAMPS), or sodium alginate. These polymers are all water-soluble or have certain compatibility with electrolyte solutions and can provide a high density of anionic sites.

[0028] The solvent is an aqueous solvent, preferably deionized water, heavy water, or a buffered aqueous solution, to ensure the full dissolution of viologen compound and polyanionic additive and the stability of the system.

[0029] The pH range of the electrolyte can be adjusted between 3 and 10 to accommodate the stability window of different viologen compounds and supporting electrolyte systems, and to avoid decomposition under acidic or strongly alkaline conditions.

[0030] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0031] Example 1 This embodiment provides sodium polystyrene sulfonate (PSS-Na) as a polyanionic electrolyte additive suitable for viologen-based aqueous organic flow batteries.

[0032] Electrochemical performance testing: Weigh 0.77 g of dichloromethyl viologen (MVCl2) and dissolve it in 30 mL of 1 mol / L potassium chloride solution. Shake and stir to prepare a 0.1 mol / L methyl viologen solution as the control electrolyte. 0.77 g of MVCl2 was dissolved in 30 mL of 1 mol / L potassium chloride solution, and the solution was shaken and stirred to prepare a 0.1 mol / L methyl viologen solution. 0.3 g of sodium polystyrene sulfonate was then added to obtain the negative electrode viologen electrolyte, which was used as the experimental sample electrolyte. The sodium polystyrene sulfonate accounted for 1 wt% of the weight of the experimental sample electrolyte.

[0033] The control electrolyte and the experimental electrolyte prepared above were subjected to cyclic voltammetry tests using a three-electrode system, with a glassy carbon electrode as the working electrode, an Ag / AgCl reference electrode, and a platinum electrode as the counter electrode.

[0034] like Figure 1 and Figure 2 As shown, the redox potentials and redox peak differences of the two electrolytes are basically the same, proving that adding sodium polystyrene sulfonate as an additive will not bring side reactions to the MV system, and the electrolyte system has good electrochemical reversibility.

[0035] Example 2 This embodiment provides sodium polystyrene sulfonate (PSS-Na) as a polyanionic electrolyte additive suitable for viologen-based aqueous organic flow batteries.

[0036] Electrochemical performance testing: Weigh 0.385 g of MVCl2 and dissolve it in 15 mL of 1 mol / L potassium chloride solution. Shake and stir to prepare a 0.1 mol / L MVCl2 solution as the control sample negative electrode electrolyte.

[0037] Weigh 0.385 g of MVCl2 and dissolve it in 15 mL of 1 mol / L potassium chloride solution. Shake and stir to prepare a 0.1 mol / L MVCl2 solution. Add 0.15 g of PSS-Na as the negative electrode electrolyte for the experimental sample. Sodium polystyrene sulfonate accounts for 1 wt% of the weight of the negative electrode electrolyte for the experimental sample.

[0038] Weigh 0.498 g of TEMPO derivative 4-(NMe3) + 4-(NMe3)-TEMPO was dissolved in 20 mL of 1 mol / L potassium chloride solution and stirred to prepare 0.1 mol / L 4-(NMe3)-TEMPO. + TEMPO solution was used as the positive electrode electrolyte.

[0039] After the negative and positive electrolytes are deoxygenated by passing nitrogen gas through them, they are stored separately in storage tanks and propelled by pumps. The two electrolytes circulate independently through pipes, circulating on both sides of a diaphragm. Redox reactions occur at the electrodes on both sides of the diaphragm. The positive and negative electrodes are connected to a power supply load; the circuit transfers electrons, and the diaphragm transfers positive and negative ions, forming a circuit. A copper plate is used as the current collector, and two graphite plates with serpentine flow channels serve as flow field plates for the positive and negative electrolytes. Graphite felt or carbon paper are used as reaction electrodes, and the positive and negative reaction electrodes are separated by a copolymer membrane of polyvinylidene chloride, polyacrylonitrile, and styrene-butadiene rubber as an ion exchange membrane.

[0040] The battery underwent long-cycle charge-discharge performance testing at 100 mA / cm². 2 The charging and discharging is performed based on the current magnitude. It can be seen that within 100 cycles, as... Figure 4 As shown, the weekly capacity decay rate of the control sample without added PSS-Na was 0.03%, and the average coulombic efficiency remained above 99.50%.

[0041] like Figure 6 As shown, the experimental sample with added PSS-Na exhibited a capacity decay rate of only 0.008% per week, and the average coulombic efficiency remained above 99.50%, demonstrating excellent cycling performance.

[0042] The charge / discharge curves of the batteries with and without PSS-Na are as follows: Figure 3 , Figure 5 As shown, the charge-discharge curves did not change significantly, indicating that the addition of PSS-Na had no significant effect on the polarization of the battery.

[0043] Example 3 This embodiment provides sodium polyacrylate as a polyanionic electrolyte additive suitable for viologen-based aqueous organic flow batteries.

[0044] Electrochemical performance testing: Weigh 0.77 g of dichloromethyl viologen (MVCl2) and dissolve it in 30 mL of 1 mol / L potassium chloride solution. Shake and stir to prepare a 0.1 mol / L methyl viologen solution as the control electrolyte. 0.77 g of MVCl2 was dissolved in 30 mL of 1 mol / L potassium chloride solution, and the solution was shaken and stirred to prepare a 0.1 mol / L methyl viologen solution. Sodium polyacrylate was then added to obtain the negative electrode viologen electrolyte, which was used as the experimental sample electrolyte. The sodium polyacrylate accounted for 20 wt% of the weight of the experimental sample electrolyte.

[0045] The control electrolyte and the experimental electrolyte prepared above were subjected to cyclic voltammetry tests using a three-electrode system, with a glassy carbon electrode as the working electrode, an Ag / AgCl reference electrode, and a platinum electrode as the counter electrode.

[0046] The redox potentials and redox peak differences of the two electrolytes are basically the same, proving that the addition of sodium polyacrylate as an additive will not bring side reactions to the MV system, and the electrolyte system has good electrochemical reversibility.

[0047] Example 4 This embodiment provides sodium polyacrylate as a polyanionic electrolyte additive suitable for viologen-based aqueous organic flow batteries.

[0048] Electrochemical performance testing: Weigh 0.385 g of MVCl2 and dissolve it in 15 mL of 1 mol / L potassium chloride solution. Shake and stir to prepare a 0.1 mol / L MVCl2 solution as the control sample negative electrode electrolyte.

[0049] Weigh 0.385 g of MVCl2 and dissolve it in 15 mL of 1 mol / L potassium chloride solution. Shake and stir to prepare a 0.1 mol / L MVCl2 solution. Add sodium polyacrylate as the negative electrode electrolyte for the experimental sample. The sodium polyacrylate constitutes 20 wt% of the negative electrode electrolyte in the experimental sample.

[0050] Weigh 0.498 g of TEMPO derivative 4-(NMe3) +4-(NMe3)-TEMPO was dissolved in 20 mL of 1 mol / L potassium chloride solution and stirred to prepare 0.1 mol / L 4-(NMe3)-TEMPO. + TEMPO solution was used as the positive electrode electrolyte.

[0051] After the negative and positive electrolytes are deoxygenated by passing nitrogen gas through them, they are stored separately in storage tanks and propelled by pumps. The two electrolytes circulate independently through pipes, circulating on both sides of a diaphragm. Redox reactions occur at the electrodes on both sides of the diaphragm. The positive and negative electrodes are connected to a power supply load; the circuit transfers electrons, and the diaphragm transfers positive and negative ions, forming a circuit. A copper plate is used as the current collector, and two graphite plates with serpentine flow channels serve as flow field plates for the positive and negative electrolytes. Graphite felt or carbon paper are used as reaction electrodes, and the positive and negative reaction electrodes are separated by a copolymer membrane of polyvinylidene chloride, polyacrylonitrile, and styrene-butadiene rubber as an ion exchange membrane.

[0052] The battery underwent long-cycle charge-discharge performance testing at 100 mA / cm². 2 The current was used for charging and discharging. It can be seen that within 100 cycles, the capacity decay rate of the control sample without sodium polyacrylate was 0.04% per week, and the coulombic efficiency remained above 99.50% on average.

[0053] The experimental sample with added sodium polyacrylate showed a capacity decay rate of only 0.009% per week and an average coulombic efficiency of over 99.50%, demonstrating excellent cycling performance.

[0054] The charge-discharge curves of batteries with and without sodium polyacrylate showed no significant changes, indicating that the addition of sodium polyacrylate had no significant effect on battery polarization.

[0055] Example 5 This embodiment provides poly(2-acrylamido-2-methylpropanesulfonate sodium salt) as a polyanionic electrolyte additive suitable for viologen-based aqueous organic flow batteries.

[0056] Electrochemical performance testing: Weigh 2.02 g of 1,1'-bis(3-(trimethylammonium)propyl)-[4,4'-bipyridine]-1,1'-dionium (quaternary ammonium cation modified viologen) and dissolve it in 30 mL of 1 mol / L potassium chloride solution. Shake and stir to prepare a 0.1 mol / L methyl viologen solution as the control electrolyte. 2.02 g of 1,1'-bis(3-(trimethylammonium)propyl)-[4,4'-bipyridine]-1,1'-dionium was weighed and dissolved in 30 mL of 1 mol / L potassium chloride solution. The solution was shaken and stirred to prepare a 0.1 mol / L methyl viologen solution. Poly(2-acrylamido-2-methylpropanesulfonate) was then added to obtain the negative electrode viologen electrolyte, which was used as the experimental sample electrolyte. The poly(2-acrylamido-2-methylpropanesulfonate) accounted for 10 wt% of the weight of the experimental sample electrolyte.

[0057] The control electrolyte and the experimental electrolyte prepared above were subjected to cyclic voltammetry tests using a three-electrode system, with a glassy carbon electrode as the working electrode, an Ag / AgCl reference electrode, and a platinum electrode as the counter electrode.

[0058] The redox potentials and redox peak differences of the two electrolytes are basically the same, proving that the addition of poly(2-acrylamido-2-methylpropanesulfonate sodium salt) as an additive will not bring side reactions to the MV system, and the electrolyte system has good electrochemical reversibility.

[0059] Example 6 This embodiment provides poly(2-acrylamido-2-methylpropanesulfonate sodium salt) as a polyanionic electrolyte additive suitable for viologen-based aqueous organic flow batteries.

[0060] Electrochemical performance testing: Weigh 1.67 g of 1,1'-bis(3-phosphonopropyl)-[4,4'-bipyridine]-1,1'-dionium-dibromosalt (phosphate-modified viologen) and dissolve it in 15 mL of 1 mol / L potassium chloride solution. Shake and stir to prepare a 0.1 mol / L 1,1-di(ethyl)-4,4-bipyridine bromide solution as the negative electrode electrolyte for the control sample.

[0061] 1.67 g of 1,1'-bis(3-phosphonopropyl)-[4,4'-bipyridine]-1,1'-diamium-dibromosalt (phosphate-modified viologen) was weighed and dissolved in 15 mL of 1 mol / L potassium chloride solution. The solution was shaken and stirred to prepare a 0.1 mol / L solution of 1,1-di(ethyl)-4,4-bipyridine bromide. Poly(2-acrylamido-2-methylpropanesulfonate) was added as the negative electrode electrolyte for the experimental sample. The poly(2-acrylamido-2-methylpropanesulfonate) accounted for 10 wt% of the weight of the negative electrode electrolyte for the experimental sample.

[0062] Weigh 0.498 g of TEMPO derivative 4-(NMe3) + 4-(NMe3)-TEMPO was dissolved in 20 mL of 1 mol / L potassium chloride solution and stirred to prepare 0.1 mol / L 4-(NMe3)-TEMPO. +TEMPO solution was used as the positive electrode electrolyte.

[0063] After the negative and positive electrolytes are deoxygenated by passing nitrogen gas through them, they are stored separately in storage tanks and propelled by pumps. The two electrolytes circulate independently through pipes, circulating on both sides of a diaphragm. Redox reactions occur at the electrodes on both sides of the diaphragm. The positive and negative electrodes are connected to a power supply load; the circuit transfers electrons, and the diaphragm transfers positive and negative ions, forming a circuit. A copper plate is used as the current collector, and two graphite plates with serpentine flow channels serve as flow field plates for the positive and negative electrolytes. Graphite felt or carbon paper are used as reaction electrodes, and the positive and negative reaction electrodes are separated by a copolymer membrane of polyvinylidene chloride, polyacrylonitrile, and styrene-butadiene rubber as an ion exchange membrane.

[0064] The battery underwent long-cycle charge-discharge performance testing at 100 mA / cm². 2 The current was used for charging and discharging. It can be seen that within 100 cycles, the capacity decay rate of the control sample without added poly(2-acrylamido-2-methylpropanesulfonate) was 0.038% per week, and the coulombic efficiency remained above 99.50% on average.

[0065] The experimental sample with added poly(2-acrylamido-2-methylpropanesulfonate) showed a capacity decay rate of only 0.01% per week and an average coulombic efficiency of over 99.50%, demonstrating excellent cycling performance.

[0066] The charge-discharge curves of batteries with and without added poly(2-acrylamido-2-methylpropanesulfonate) showed no significant changes, indicating that the addition of poly(2-acrylamido-2-methylpropanesulfonate) had no significant effect on the polarization of the battery.

[0067] Example 7 This embodiment provides sodium polystyrene sulfonate as a polyanionic electrolyte additive suitable for viologen-based aqueous organic flow batteries.

[0068] Electrochemical performance testing: Dissolve 0.8 g of diethyl viologen chloride in 30 mL of 1 mol / L potassium chloride solution, and shake and stir to prepare a 0.1 mol / L viologen solution as the control electrolyte. 0.8 g of diethyl viologen chloride was dissolved in 30 mL of 1 mol / L potassium chloride solution, and the solution was shaken and stirred to prepare a 0.1 mol / L methyl viologen solution. Sodium polystyrene sulfonate was then added to obtain the negative electrode viologen electrolyte, which was used as the experimental sample electrolyte. The sodium polystyrene sulfonate accounted for 1 wt% of the weight of the experimental sample electrolyte.

[0069] The control electrolyte and the experimental electrolyte prepared above were subjected to cyclic voltammetry tests using a three-electrode system, with a glassy carbon electrode as the working electrode, an Ag / AgCl reference electrode, and a platinum electrode as the counter electrode.

[0070] The redox potentials and redox peak differences of the two electrolytes are basically the same, proving that the addition of sodium polystyrene sulfonate as an additive will not bring side reactions to the MV system, and the electrolyte system has good electrochemical reversibility.

[0071] Example 8 This embodiment provides sodium polystyrene sulfonate as a polyanionic electrolyte additive suitable for viologen-based aqueous organic flow batteries.

[0072] Electrochemical performance testing: Weigh 0.4 g of diethyl viologen chloride and dissolve it in 15 mL of 1 mol / L potassium chloride solution. Shake and stir to prepare a 0.1 mol / L viologen solution as the negative electrode electrolyte for the control sample.

[0073] Weigh 0.4 g of diethyl viologen chloride and dissolve it in 15 mL of 1 mol / L potassium chloride solution. Shake and stir to prepare a 0.1 mol / L viologen solution. Add sodium polystyrene sulfonate as the negative electrode electrolyte for the experimental sample. The sodium polystyrene sulfonate accounts for 0.1 wt% of the negative electrode electrolyte in the experimental sample.

[0074] Weigh 0.498 g of TEMPO derivative 4-(NMe3) + 4-(NMe3)-TEMPO was dissolved in 20 mL of 1 mol / L potassium chloride solution and stirred to prepare 0.1 mol / L 4-(NMe3)-TEMPO. + TEMPO solution was used as the positive electrode electrolyte.

[0075] After the negative and positive electrolytes are deoxygenated by passing nitrogen gas through them, they are stored separately in storage tanks and propelled by pumps. The two electrolytes circulate independently through pipes, circulating on both sides of a diaphragm. Redox reactions occur at the electrodes on both sides of the diaphragm. The positive and negative electrodes are connected to a power supply load; the circuit transfers electrons, and the diaphragm transfers positive and negative ions, forming a circuit. A copper plate is used as the current collector, and two graphite plates with serpentine flow channels serve as flow field plates for the positive and negative electrolytes. Graphite felt or carbon paper are used as reaction electrodes, and the positive and negative reaction electrodes are separated by a copolymer membrane of polyvinylidene chloride, polyacrylonitrile, and styrene-butadiene rubber as an ion exchange membrane.

[0076] The battery underwent long-cycle charge-discharge performance testing at 100 mA / cm². 2The current was used for charging and discharging. It can be seen that within 100 cycles, the capacity decay rate of the control sample without sodium polystyrene sulfonate was 0.035% per week, and the coulombic efficiency remained above 99.50% on average.

[0077] The experimental sample with added sodium polystyrene sulfonate showed a capacity decay rate of only 0.009% per week and an average coulombic efficiency of over 99.50%, demonstrating excellent cycling performance.

[0078] The charge-discharge curves of batteries with and without added sodium polystyrene sulfonate showed no significant changes, indicating that the addition of sodium polystyrene sulfonate had no significant effect on battery polarization.

[0079] Alkali metal chlorides can be selected from sodium chloride (NaCl), potassium chloride (KCl), lithium chloride (LiCl), etc.; alkaline earth metal chlorides include magnesium chloride (MgCl2), calcium chloride (CaCl2), etc. These chlorides have high solubility and excellent ion dissociation ability, which can effectively increase the cation concentration in the electrolyte and promote charge transport. Alkali metal sulfates such as sodium sulfate (Na2SO4) and potassium sulfate (K2SO4), and alkaline earth metal sulfates such as magnesium sulfate (MgSO4) and calcium sulfate (CaSO4), have anions such as SO42-. 2- Highly stable and resistant to oxidation and decomposition over a wide potential window, these electrolytes are suitable for long-term cyclic operation in flow battery systems. Alkali metal phosphates, such as sodium dihydrogen phosphate (NaH2PO4) and dipotassium hydrogen phosphate (K2HPO4), and alkaline earth metal phosphates, such as magnesium phosphate (Mg3(PO4)2), not only possess excellent buffering capacity, helping to maintain electrolyte pH stability, but also reduce the risk of viologen molecule hydrolysis under extreme acid and alkaline conditions. Alkali metal sulfonates, such as sodium methanesulfonate (CH3SO3Na) and potassium p-toluenesulfonate (C7H7SO3K), and alkaline earth metal sulfonates, such as magnesium methanesulfonate ((CH3SO3)2Mg), can further improve the interfacial behavior and wettability of the electrolyte due to the steric hindrance effect and hydrophilicity of their organic anions.

[0080] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the protection scope of the present invention.

Claims

1. An electrolyte containing a polyanionic electrolyte additive, characterized in that, Including viologen compounds, supporting electrolytes, solvents, and polyanionic electrolyte additives; The polyanionic electrolyte additive accounts for 0.1% to 20 wt% by mass. The polyanionic electrolyte additive is rich in a variety of negatively charged functional groups, which are used to interfere with the π-π stacking behavior of viologen molecules. The polyanionic electrolyte additive is a polymer containing repeating units.

2. The electrolyte containing a polyanionic electrolyte additive according to claim 1, characterized in that, The polymer containing repeating units is sodium polystyrene sulfonate, sodium polyacrylate, poly(2-acrylamido-2-methylpropanesulfonate) or sodium alginate.

3. The electrolyte containing a polyanionic electrolyte additive according to claim 1, characterized in that, The viologen compounds are viologen derivatives with various structural types.

4. The electrolyte containing a polyanionic electrolyte additive according to claim 3, characterized in that, Viologen derivatives include one or more of the following: alkyl-substituted viologen, quaternary ammonium cation-modified viologen, sulfonate-modified viologen, phosphate-modified viologen, carboxylic acid hydroxyl-modified viologen, and hydroxyl-modified viologen.

5. The electrolyte containing a polyanionic electrolyte additive according to claim 1, characterized in that, The supporting electrolyte includes one or more of alkali metal chlorides, alkaline earth metal chlorides, alkali metal sulfates, alkaline earth metal sulfates, alkali metal phosphates, alkaline earth metal phosphates, alkali metal sulfonates, and alkaline earth metal sulfonates.

6. The electrolyte containing a polyanionic electrolyte additive according to claim 1, characterized in that, The pH value of the electrolyte is between 3 and 10.

7. The electrolyte containing a polyanionic electrolyte additive according to claim 1, characterized in that, The solvent is an aqueous solvent.

8. The electrolyte containing a polyanionic electrolyte additive according to claim 7, characterized in that, The aqueous solvent is deionized water, heavy water, or a buffer solution.

9. The electrolyte containing a polyanionic electrolyte additive according to claim 1, characterized in that, The electrolyte is suitable for redox flow battery systems.

10. A flow battery, comprising a positive electrode electrolyte, a negative electrode electrolyte, and a separator separating the two, characterized in that, The negative electrode electrolyte is the electrolyte containing polyanionic electrolyte additives as described in any one of claims 1 to 9.

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