A vanadium redox flow battery electrolyte and battery

Abstract

This invention belongs to the field of battery electrolyte preparation technology, specifically a vanadium redox flow battery electrolyte and battery. The electrolyte consists of a base electrolyte, a primary additive, and a secondary additive. The base electrolyte contains vanadium ions, sulfate ions, and hydrogen ions. During the charge and discharge process of the vanadium redox flow battery, the vanadium ions in the positive electrode electrolyte are tetravalent and pentavalent, while those in the negative electrode electrolyte are divalent and trivalent. The primary additive is methanesulfonic acid or potassium methanesulfonate. The secondary additive is at least one of polyethylene glycol, polyacrylic acid, polyvinylpyrrolidone, polyacrylamide, and polystyrene sulfonic acid. The mass fraction ratio of the secondary additive to the primary additive is 0.002% ≤ w(secondary additive) / w(primary additive) ≤ 60%. This electrolyte effectively avoids the problems caused by the aggregation of methanesulfonic acid-vanadium complexes during battery operation, improving the overall performance and lifespan of the battery.

Description

Technical Field

[0001] This invention belongs to the field of battery electrolyte preparation technology, specifically a vanadium redox flow battery electrolyte and its preparation method. Background Technology

[0002] Vanadium redox flow batteries (VRBs), as a large-scale energy storage technology with broad application prospects, have attracted much attention in fields such as renewable energy storage and grid peak shaving due to their advantages such as independently designable power and capacity, long cycle life, high safety, and environmental friendliness. VRBs achieve energy storage and release through the reversible transformation of vanadium ions between different valence states. The electrolyte, as a core component of VRBs, directly affects key indicators such as energy density, charge / discharge efficiency, and cycle stability.

[0003] To improve the performance of vanadium redox flow battery electrolytes, researchers have explored introducing various additives. Methanesulfonic acid or potassium methanesulfonate has been introduced as an additive. Methanesulfonic acid possesses good conductivity and chemical stability, enhancing the electrolyte's conductivity and increasing the electrochemical activity of vanadium ions, thus improving the battery's charge-discharge performance to some extent. Potassium methanesulfonate can also play a similar role in the electrolyte, optimizing its electrochemical environment.

[0004] However, further research revealed new problems when the introduced methanesulfonic acid content was too high or its presence in the electrolyte for too long. Methanesulfonic acid forms methanesulfonic acid-vanadium complexes with vanadium ions, and these complexes are prone to aggregation. This aggregation has a series of adverse effects. On the one hand, the aggregated complexes increase the viscosity of the electrolyte, hindering the transport of vanadium ions and reducing the electrolyte utilization rate, thus affecting the battery's energy density and charge / discharge efficiency. On the other hand, the formation of agglomerates may disrupt the stability of the electrolyte, accelerate battery capacity decay, and shorten the battery's cycle life.

[0005] Therefore, developing an electrolyte for all-vanadium redox flow batteries that can reasonably control the ratio of primary additives to vanadium ion concentrations and the ratio of secondary additives to primary additives, and effectively solve the problem of methanesulfonic acid-vanadium complex agglomeration, is of great practical significance for improving the performance and stability of all-vanadium redox flow batteries and promoting their widespread application in the energy storage field. Summary of the Invention

[0006] To address the performance deficiencies of existing vanadium redox flow battery electrolytes caused by methanesulfonic acid-related issues, this invention provides a high-performance vanadium redox flow battery electrolyte and a vanadium redox flow battery using this electrolyte. In this invention, by introducing secondary additives such as polyethylene glycol, polyacrylic acid, polyvinylpyrrolidone, polyacrylamide, or polystyrene sulfonic acid as dispersants and precisely controlling their ratio with primary additives, the methanesulfonic acid-vanadium complex aggregates can be effectively dispersed. This avoids problems such as increased electrolyte viscosity and reduced utilization caused by agglomeration, maintains electrolyte stability, and extends the effective service life of the electrolyte.

[0007] To achieve the above-mentioned objectives, the specific technical solution of this invention is as follows: This invention discloses an electrolyte for a vanadium redox flow battery, comprising a base electrolyte, primary additives, and secondary additives. The base electrolyte, as the core component, contains vanadium ions, sulfate ions, and hydrogen ions. During the charge and discharge process of the vanadium redox flow battery, vanadium ions in the positive electrode electrolyte participate in the electrochemical reaction in tetravalent and pentavalent states, while vanadium ions in the negative electrode electrolyte react in divalent and trivalent states. This reversible transformation of vanadium ions into different valence states enables the storage and release of electrical energy.

[0008] In a preferred embodiment of this application, in the vanadium redox flow battery electrolyte, the total molar concentration of vanadium ions in the base electrolyte is controlled at 1.5M-2.4M, the molar concentration of sulfate ions is 2.2M-5M, and the molar concentration of hydrogen ions is 2.2M-10M. This concentration range is set to ensure that the base electrolyte has good electrochemical performance and stability, providing a basic guarantee for the normal operation of the battery.

[0009] In a preferred embodiment of this application, the primary additive in the vanadium redox flow battery electrolyte is methanesulfonic acid or potassium methanesulfonate. When the primary additive is methanesulfonic acid, its molar concentration in the electrolyte ranges from 0.001M to 0.1M; when it is potassium methanesulfonate, the molar concentration range is also 0.001M to 0.1M. The introduction of methanesulfonic acid or potassium methanesulfonate can improve the electrochemical environment of the electrolyte, enhance its conductivity, increase the electrochemical activity of vanadium ions, and improve the charge-discharge performance of the battery to a certain extent. However, when the methanesulfonic acid content is too high or its presence in the electrolyte for too long, it will form methanesulfonic acid-vanadium complexes with vanadium ions. These complexes are prone to aggregation, leading to problems such as increased electrolyte viscosity, reduced utilization rate, and decreased stability.

[0010] To address the complex aggregation problem caused by the introduction of methanesulfonic acid, this invention introduces a secondary additive, which is at least one of polyethylene glycol, polyacrylic acid, polyvinylpyrrolidone, polyacrylamide, and polystyrene sulfonic acid. This secondary additive acts as a dispersant. The mass percentage of the secondary additive in the electrolyte is 0.005% - 1.5%. Specifically, the molecular weight of polyethylene glycol is controlled between 400 and 1500, the molecular weight of polyacrylic acid is 800 - 4000, the molecular weight of polyvinylpyrrolidone is controlled between 500 and 100,000, the molecular weight of polyacrylamide is controlled between 500 and 600,000, and the molecular weight of polystyrene sulfonic acid is controlled between 600 and 500,000. Polyethylene glycol, polyacrylic acid, polyvinylpyrrolidone, polyacrylamide, or polystyrene sulfonic acid of different molecular weights can be used alone or in combination according to actual needs. They can play a dispersing role in the electrolyte, preventing the aggregation of the methanesulfonic acid-vanadium complex and maintaining the stability and good performance of the electrolyte.

[0011] Furthermore, to ensure that the primary and secondary additives can work synergistically for optimal effect, this invention precisely controls the ratio of primary additive to vanadium ion concentration and the ratio of secondary additive to primary additive dosage. When the primary additive is methanesulfonic acid, the ratio is controlled to be 0.025 ≤ c(CH3SO3H) / c(V) ≤ 1.5625; when the primary additive is potassium methanesulfonate, the ratio is controlled to be 0.025 ≤ c(CH3SO3K) / c(V) ≤ 1.5625. Simultaneously, when the primary additive is methanesulfonic acid, the ratio is controlled to be 0.002% ≤ w(secondary additive) / w(CH3SO3H) ≤ 60%; when the primary additive is potassium methanesulfonate, the ratio is controlled to be 0.002% ≤ w(secondary additive) / w(CH3SO3K) ≤ 60%. By setting these ratio ranges, problems caused by the aggregation of methanesulfonic acid-vanadium complexes can be effectively avoided, the roles of each additive can be fully utilized, and the electrolyte performance can be optimized.

[0012] The present invention also provides a vanadium redox flow battery, which uses the vanadium redox flow battery electrolyte as described above.

[0013] As a preferred embodiment of this application, a vanadium redox flow battery includes a positive electrode, a negative electrode, a separator, and a storage tank and piping system for storing and circulating the electrolyte. The electrolyte used for both the positive and negative electrodes is the vanadium redox flow battery electrolyte provided by the present invention. This electrolyte effectively avoids the problems caused by the aggregation of methanesulfonic acid-vanadium complexes during battery operation, improving the overall performance and lifespan of the battery, and providing strong support for the widespread application of vanadium redox flow batteries in the energy storage field. Therefore, the applicant also protects the application of the vanadium redox flow battery electrolyte described above in effectively avoiding the aggregation of methanesulfonic acid-vanadium complexes during battery operation, thereby improving the overall performance and lifespan of the battery.

[0014] Compared with existing technologies, the beneficial effects of this invention are: (1) Optimize electrolyte performance and improve battery charge and discharge efficiency: By rationally introducing methanesulfonic acid or potassium methanesulfonate as primary additives and precisely controlling their concentration and the concentration ratio with vanadium ions, the electrochemical environment of the electrolyte is effectively improved, the conductivity of the electrolyte is enhanced, the electrochemical activity of vanadium ions is increased, and thus the charge and discharge performance of the all-vanadium redox flow battery is improved.

[0015] (2) Solving the problem of complex aggregation and maintaining electrolyte stability: Polyethylene glycol, polyacrylic acid, polyvinylpyrrolidone, polyacrylamide or polystyrene sulfonic acid are introduced as secondary additives as dispersants, and the ratio of their addition to the primary additives is precisely controlled. This can effectively disperse the methanesulfonic acid-vanadium complex aggregates, avoid problems such as increased electrolyte viscosity and reduced utilization caused by aggregation, maintain the stability of the electrolyte, and extend the effective service life of the electrolyte.

[0016] (3) Improve the overall performance and service life of the battery and promote application development: The vanadium redox flow battery using the electrolyte of the present invention can effectively avoid the adverse effects of the aggregation of vanadium methanesulfonic acid-vanadium complex, significantly improve the overall performance and extend the service life, and lay a solid foundation for the widespread application of vanadium redox flow batteries in the field of energy storage. Detailed Implementation

[0017] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0018] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of this application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0019] It should be noted that the terminology used herein is for the purpose of describing particular implementations only and is not intended to limit the exemplary implementations according to this application. As used herein, the singular form includes the plural form unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this description, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0020] In this invention, some conventional operating equipment, devices and components have been omitted or only briefly described.

[0021] Unless otherwise specified in the examples, the conditions shall be performed according to the standard conditions or the conditions recommended by the manufacturer.

[0022] In this application, w refers to the quality fraction.

[0023] Example 1: 1. Preparation of electrolyte for all-vanadium redox flow batteries The basic electrolyte (existing technology) has a volume of 100 ml, with a total vanadium ion concentration of 1.7 mol / L, a sulfate ion concentration of 4.3 mol / L, and a hydrogen ion concentration of 6 mol / L. Methylsulfonic acid of 0.005 M is introduced into the basic electrolyte.

[0024] 2. Conductivity test The electrolyte volume was 50 ml, and the conductivity was tested using a conductivity standard calibration solution.

[0025] 3. Viscosity test The electrolyte volume was 50 ml, and the viscosity was tested using an Ubbelohde viscometer.

[0026] 4. Battery assembly: A vanadium redox flow battery, wherein the battery is arranged in sequence with a positive electrode plate and a positive bipolar plate (7.5 × 9.5 cm). 2 ), positive electrode (6×8 cm) 2 ), ion-conducting membrane (Nafion 212), negative electrode (6×8 cm) 2 ), negative bipolar plate (7.5×9.5cm) 2 The negative end plate is assembled.

[0027] 5. Battery test: The charge-discharge cycle was performed at 25 °C with an electrolyte flow rate of 50 ml / min and a charge-discharge current density of 200 mA cm⁻¹. -2 The operating voltage is 1 V to 1.55 V.

[0028] Example 2 1. Preparation of electrolyte for all-vanadium redox flow batteries The basic electrolyte (existing technology) has a volume of 100 ml, with a total vanadium ion concentration of 1.7 mol / L, a sulfate ion concentration of 4.3 mol / L, a hydrogen ion concentration of 6 mol / L, and 0.005 M potassium methanesulfonate is introduced.

[0029] 2. Conductivity test The electrolyte volume was 50 ml, and the conductivity was tested using a conductivity standard calibration solution.

[0030] 3. Viscosity test The electrolyte volume was 50 ml, and the viscosity was tested using an Ubbelohde viscometer.

[0031] 4. Battery assembly: A vanadium redox flow battery, wherein the battery is arranged in sequence with a positive electrode plate and a positive bipolar plate (7.5 × 9.5 cm). 2 ), positive electrode (6×8 cm) 2 ), ion-conducting membrane (Nafion 212), negative electrode (6×8 cm) 2 ), negative bipolar plate (7.5×9.5cm) 2 The negative end plate is assembled.

[0032] 5. Battery test: The charge-discharge cycle was performed at 25 °C with an electrolyte flow rate of 50 ml / min and a charge-discharge current density of 200 mA cm⁻¹. -2 The operating voltage is 1 V to 1.55 V.

[0033] Example 3 1. Preparation of electrolyte for all-vanadium redox flow batteries The basic electrolyte (existing technology) has a volume of 100 ml, with a total vanadium ion concentration of 1.7 mol / L, a sulfate ion concentration of 4.3 mol / L, a hydrogen ion concentration of 6 mol / L, and 0.01 M potassium methanesulfonate is introduced.

[0034] 2. Conductivity test The electrolyte volume was 50 ml, and the conductivity was tested using a conductivity standard calibration solution.

[0035] 3. Viscosity test The electrolyte volume was 50 ml, and the viscosity was tested using an Ubbelohde viscometer.

[0036] 4. Battery assembly: A vanadium redox flow battery, wherein the battery is arranged in sequence with a positive electrode plate and a positive bipolar plate (7.5 × 9.5 cm). 2 ), positive electrode (6×8 cm) 2 ), ion-conducting membrane (Nafion 212), negative electrode (6×8 cm) 2 ), negative bipolar plate (7.5×9.5cm) 2 The negative end plate is assembled.

[0037] 5. Battery test: The charge-discharge cycle was performed at 25 °C with an electrolyte flow rate of 50 ml / min and a charge-discharge current density of 200 mA cm⁻¹. -2 The operating voltage is 1 V to 1.55 V.

[0038] Example 4 1. Preparation of electrolyte for all-vanadium redox flow batteries The basic electrolyte (existing technology) has a volume of 100 ml, with a total vanadium ion concentration of 1.7 mol / L, a sulfate ion concentration of 4.3 mol / L, a hydrogen ion concentration of 6 mol / L, and 0.1 M potassium methanesulfonate is introduced.

[0039] 2. Conductivity test The electrolyte volume was 50 ml, and the conductivity was tested using a conductivity standard calibration solution.

[0040] 3. Viscosity test The electrolyte volume was 50 ml, and the viscosity was tested using an Ubbelohde viscometer.

[0041] 4. Battery assembly: A vanadium redox flow battery, wherein the battery is arranged in sequence with a positive electrode plate and a positive bipolar plate (7.5 × 9.5 cm). 2 ), positive electrode (6×8 cm) 2 ), ion-conducting membrane (Nafion 212), negative electrode (6×8 cm) 2 ), negative bipolar plate (7.5×9.5cm) 2 The negative end plate is assembled.

[0042] 5. Battery test: The charge-discharge cycle was performed at 25 °C with an electrolyte flow rate of 50 ml / min and a charge-discharge current density of 200 mA cm⁻¹. -2 The operating voltage is 1 V to 1.55 V.

[0043] Example 5 1. Preparation of electrolyte for all-vanadium redox flow batteries The basic electrolyte (existing technology) has a volume of 100 ml, with a total vanadium ion concentration of 1.7 mol / L, a sulfate ion concentration of 4.3 mol / L, a hydrogen ion concentration of 6 mol / L, and 0.01 M potassium methanesulfonate and 0.005 wt% polyethylene glycol with a molecular weight of 800.

[0044] 2. Conductivity test The electrolyte volume was 50 ml, and the conductivity was tested using a conductivity standard calibration solution.

[0045] 3. Viscosity test The electrolyte volume was 50 ml, and the viscosity was tested using an Ubbelohde viscometer.

[0046] 4. Battery assembly: A vanadium redox flow battery, wherein the battery is arranged in sequence with a positive electrode plate and a positive bipolar plate (7.5 × 9.5 cm). 2 ), positive electrode (6×8 cm) 2 ), ion-conducting membrane (Nafion 212), negative electrode (6×8 cm) 2 ), negative bipolar plate (7.5×9.5cm) 2 The negative end plate is assembled.

[0047] 5. Battery test: The charge-discharge cycle was performed at 25 °C with an electrolyte flow rate of 50 ml / min and a charge-discharge current density of 200 mA cm⁻¹. -2 The operating voltage is 1 V to 1.55 V.

[0048] Example 6 1. Preparation of electrolyte for all-vanadium redox flow batteries The basic electrolyte (existing technology) has a volume of 100 ml, with a total vanadium ion concentration of 1.7 mol / L, a sulfate ion concentration of 4.3 mol / L, a hydrogen ion concentration of 6 mol / L, and 0.01 M potassium methanesulfonate and 0.005 wt% polyacrylic acid with a molecular weight of 800.

[0049] 2. Conductivity test The electrolyte volume was 50 ml, and the conductivity was tested using a conductivity standard calibration solution.

[0050] 3. Viscosity test The electrolyte volume was 50 ml, and the viscosity was tested using an Ubbelohde viscometer.

[0051] 4. Battery assembly: A vanadium redox flow battery, wherein the battery is arranged in sequence with a positive electrode plate and a positive bipolar plate (7.5 × 9.5 cm). 2 ), positive electrode (6×8 cm) 2 ), ion-conducting membrane (Nafion 212), negative electrode (6×8 cm) 2 ), negative bipolar plate (7.5×9.5cm) 2 The negative end plate is assembled.

[0052] 5. Battery test: The charge-discharge cycle was performed at 25 °C with an electrolyte flow rate of 50 ml / min and a charge-discharge current density of 200 mA cm⁻¹. -2 The operating voltage is 1 V to 1.55 V.

[0053] Example 7 1. Preparation of electrolyte for all-vanadium redox flow batteries The basic electrolyte (existing technology) has a volume of 100 ml, with a total vanadium ion concentration of 1.7 mol / L, a sulfate ion concentration of 4.3 mol / L, a hydrogen ion concentration of 6 mol / L, and 0.01 M potassium methanesulfonate and 0.005 wt% polyvinylpyrrolidone with a molecular weight of 800.

[0054] 2. Conductivity test The electrolyte volume was 50 ml, and the conductivity was tested using a conductivity standard calibration solution.

[0055] 3. Viscosity test The electrolyte volume was 50 ml, and the viscosity was tested using an Ubbelohde viscometer.

[0056] 4. Battery assembly: A vanadium redox flow battery, wherein the battery is arranged in sequence with a positive electrode plate and a positive bipolar plate (7.5 × 9.5 cm). 2 ), positive electrode (6×8 cm) 2 ), ion-conducting membrane (Nafion 212), negative electrode (6×8 cm) 2 ), negative bipolar plate (7.5×9.5cm) 2 The negative end plate is assembled.

[0057] 5. Battery test: The charge-discharge cycle was performed at 25 °C with an electrolyte flow rate of 50 ml / min and a charge-discharge current density of 200 mA cm⁻¹. -2 The operating voltage is 1 V to 1.55 V.

[0058] Example 8 1. Preparation of electrolyte for all-vanadium redox flow batteries The basic electrolyte (existing technology) has a volume of 100 ml, with a total vanadium ion concentration of 1.7 mol / L, a sulfate ion concentration of 4.3 mol / L, a hydrogen ion concentration of 6 mol / L, and 0.01 M potassium methanesulfonate and 0.005 wt% polyacrylamide with a molecular weight of 800.

[0059] 2. Conductivity test The electrolyte volume was 50 ml, and the conductivity was tested using a conductivity standard calibration solution.

[0060] 3. Viscosity test The electrolyte volume was 50 ml, and the viscosity was tested using an Ubbelohde viscometer.

[0061] 4. Battery assembly: A vanadium redox flow battery, wherein the battery is arranged in sequence with a positive electrode plate and a positive bipolar plate (7.5 × 9.5 cm). 2 ), positive electrode (6×8 cm) 2 ), ion-conducting membrane (Nafion 212), negative electrode (6×8 cm) 2 ), negative bipolar plate (7.5×9.5cm) 2 The negative end plate is assembled.

[0062] 5. Battery test: The charge-discharge cycle was performed at 25 °C with an electrolyte flow rate of 50 ml / min and a charge-discharge current density of 200 mA cm⁻¹. -2 The operating voltage is 1 V to 1.55 V.

[0063] Example 9 1. Preparation of electrolyte for all-vanadium redox flow batteries The basic electrolyte (existing technology) has a volume of 100 ml, with a total vanadium ion concentration of 1.7 mol / L, a sulfate ion concentration of 4.3 mol / L, a hydrogen ion concentration of 6 mol / L, and 0.01 M potassium methanesulfonate and 0.005 wt% polystyrene sulfonic acid with a molecular weight of 800.

[0064] 2. Conductivity test The electrolyte volume was 50 ml, and the conductivity was tested using a conductivity standard calibration solution.

[0065] 3. Viscosity test The electrolyte volume was 50 ml, and the viscosity was tested using an Ubbelohde viscometer.

[0066] 4. Battery assembly: A vanadium redox flow battery, wherein the battery is arranged in sequence with a positive electrode plate and a positive bipolar plate (7.5 × 9.5 cm).2 ), positive electrode (6×8 cm) 2 ), ion-conducting membrane (Nafion 212), negative electrode (6×8 cm) 2 ), negative bipolar plate (7.5×9.5cm) 2 The negative end plate is assembled.

[0067] 5. Battery test: The charge-discharge cycle was performed at 25 °C with an electrolyte flow rate of 50 ml / min and a charge-discharge current density of 200 mA cm⁻¹. -2 The operating voltage is 1 V to 1.55 V.

[0068] Example 10 1. Preparation of electrolyte for all-vanadium redox flow batteries The basic electrolyte (existing technology) has a volume of 100 ml, with a total vanadium ion concentration of 1.7 mol / L, a sulfate ion concentration of 4.3 mol / L, a hydrogen ion concentration of 6 mol / L, and 0.01 M potassium methanesulfonate and 0.01 wt% polyethylene glycol with a molecular weight of 800.

[0069] 2. Conductivity test The electrolyte volume was 50 ml, and the conductivity was tested using a conductivity standard calibration solution.

[0070] 3. Viscosity test The electrolyte volume was 50 ml, and the viscosity was tested using an Ubbelohde viscometer.

[0071] 4. Battery assembly: A vanadium redox flow battery, wherein the battery is arranged in sequence with a positive electrode plate and a positive bipolar plate (7.5 × 9.5 cm). 2 ), positive electrode (6×8 cm) 2 ), ion-conducting membrane (Nafion 212), negative electrode (6×8 cm) 2 ), negative bipolar plate (7.5×9.5cm) 2 The negative end plate is assembled.

[0072] 5. Battery test: The charge-discharge cycle was performed at 25 °C with an electrolyte flow rate of 50 ml / min and a charge-discharge current density of 200 mA cm⁻¹. -2 The operating voltage is 1 V to 1.55 V.

[0073] Example 11 1. Preparation of electrolyte for all-vanadium redox flow batteries The basic electrolyte (existing technology) has a volume of 100 ml, with a total vanadium ion concentration of 1.7 mol / L, a sulfate ion concentration of 4.3 mol / L, a hydrogen ion concentration of 6 mol / L, and 0.01 M potassium methanesulfonate and 0.1 wt% polyethylene glycol with a molecular weight of 800.

[0074] 2. Conductivity test The electrolyte volume was 50 ml, and the conductivity was tested using a conductivity standard calibration solution.

[0075] 3. Viscosity test The electrolyte volume was 50 ml, and the viscosity was tested using an Ubbelohde viscometer.

[0076] 4. Battery assembly: A vanadium redox flow battery, wherein the battery is arranged in sequence with a positive electrode plate and a positive bipolar plate (7.5 × 9.5 cm). 2 ), positive electrode (6×8 cm) 2 ), ion-conducting membrane (Nafion 212), negative electrode (6×8 cm) 2 ), negative bipolar plate (7.5×9.5cm) 2 The negative end plate is assembled.

[0077] 5. Battery test: The charge-discharge cycle was performed at 25 °C with an electrolyte flow rate of 50 ml / min and a charge-discharge current density of 200 mA cm⁻¹. -2 The operating voltage is 1 V to 1.55 V.

[0078] Example 12 1. Preparation of electrolyte The basic electrolyte (existing technology) has a volume of 100 ml, with a total vanadium ion concentration of 1.7 mol / L, a sulfate ion concentration of 4.3 mol / L, a hydrogen ion concentration of 6 mol / L, and 0.01 M potassium methanesulfonate and 0.5 wt% polyethylene glycol with a molecular weight of 800.

[0079] 2. Conductivity test The electrolyte volume was 50 ml, and the conductivity was tested using a conductivity standard calibration solution.

[0080] 3. Viscosity test The electrolyte volume was 50 ml, and the viscosity was tested using an Ubbelohde viscometer.

[0081] 4. Battery assembly: A vanadium redox flow battery, wherein the battery is arranged in sequence with a positive electrode plate and a positive bipolar plate (7.5 × 9.5 cm). 2), positive electrode (6×8 cm) 2 ), ion-conducting membrane (Nafion 212), negative electrode (6×8 cm) 2 ), negative bipolar plate (7.5×9.5cm) 2 The negative end plate is assembled.

[0082] 5. Battery test: The charge-discharge cycle was performed at 25 °C with an electrolyte flow rate of 50 ml / min and a charge-discharge current density of 200 mA cm⁻¹. -2 The operating voltage is 1 V to 1.55 V.

[0083] Example 13 1. Preparation of electrolyte The basic electrolyte (existing technology) has a volume of 100 ml, with a total vanadium ion concentration of 1.7 mol / L, a sulfate ion concentration of 4.3 mol / L, a hydrogen ion concentration of 6 mol / L, and 0.01 M potassium methanesulfonate and 1 wt% polyethylene glycol with a molecular weight of 800.

[0084] 2. Conductivity test The electrolyte volume was 50 ml, and the conductivity was tested using a conductivity standard calibration solution.

[0085] 3. Viscosity test The electrolyte volume was 50 ml, and the viscosity was tested using an Ubbelohde viscometer.

[0086] 4. Battery assembly: A vanadium redox flow battery, wherein the battery is arranged in sequence with a positive electrode plate and a positive bipolar plate (7.5 × 9.5 cm). 2 ), positive electrode (6×8 cm) 2 ), ion-conducting membrane (Nafion 212), negative electrode (6×8 cm) 2 ), negative bipolar plate (7.5×9.5cm) 2 The negative end plate is assembled.

[0087] 5. Battery test: The charge-discharge cycle was performed at 25 °C with an electrolyte flow rate of 50 ml / min and a charge-discharge current density of 200 mA cm⁻¹. -2 The operating voltage is 1 V to 1.55 V.

[0088] Example 14 1. Preparation of electrolyte The basic electrolyte (existing technology) has a volume of 100 ml, with a total vanadium ion concentration of 1.7 mol / L, a sulfate ion concentration of 4.3 mol / L, a hydrogen ion concentration of 6 mol / L, and 0.01 M potassium methanesulfonate and 1.5 wt% polyethylene glycol with a molecular weight of 800.

[0089] 2. Conductivity test The electrolyte volume was 50 ml, and the conductivity was tested using a conductivity standard calibration solution.

[0090] 3. Viscosity test The electrolyte volume was 50 ml, and the viscosity was tested using an Ubbelohde viscometer.

[0091] 4. Battery assembly: A vanadium redox flow battery, wherein the battery is arranged in sequence with a positive electrode plate and a positive bipolar plate (7.5 × 9.5 cm). 2 ), positive electrode (6×8 cm) 2 ), ion-conducting membrane (Nafion 212), negative electrode (6×8 cm) 2 ), negative bipolar plate (7.5×9.5cm) 2 The negative end plate is assembled.

[0092] 5. Battery test: The charge-discharge cycle was performed at 25 °C with an electrolyte flow rate of 50 ml / min and a charge-discharge current density of 200 mA cm⁻¹. -2 The operating voltage is 1 V to 1.55 V.

[0093] experiment: The electrolytes in Examples 1-14 were tested respectively, and the specific details are as follows: 1. The conductivity and viscosity of the electrolytes in Examples 1 and 2 were compared, as shown in Table 1: Table 1. Comparison of viscosity and conductivity between Example 1 and Example 2:

[0094] As shown in Table 1, when methanesulfonic acid and potassium methanesulfonate are introduced at the same concentrations, potassium methanesulfonate has a better effect on reducing viscosity and increasing conductivity. This indicates that the high charge density protons ionized from methanesulfonic acid strengthen the network structure of the solution, thereby increasing viscosity. On the other hand, the potassium ions introduced by potassium methanesulfonate can effectively "weaken" this structure, effectively reducing the viscosity of the system. At the same time, the introduction of potassium ions also directly increases the number of charge carriers, which makes a significant contribution to improving conductivity.

[0095] 2. The conductivity and viscosity of the electrolytes in Examples 2-4 were compared and are shown in Table 2: Table 2 Comparison of viscosity and conductivity in Examples 2-4:

[0096] As shown in Table 2, with the gradual increase of potassium methanesulfonate concentration, the viscosity first gradually decreases and then increases, while the conductivity gradually increases and then decreases. When potassium methanesulfonate is present in the electrolyte, the presence of methanesulfonate ions can compete for coordination and disrupt the hydrogen bond network, significantly reducing the internal resistance of electrolyte flow and increasing the concentration of freely moving charge carriers in the solution, thereby improving electrolyte performance. However, with further increases in concentration, excessive methanesulfonate ions will form methanesulfonate-vanadium complexes with vanadium ions. These complexes are prone to aggregation, which in turn increases the viscosity of the electrolyte and hinders the transport of vanadium ions.

[0097] 3. The conductivity and viscosity of the electrolytes in Examples 3 and 5-9 were compared and the results are shown in Table 3. Table 3 Comparison of viscosity and conductivity in Examples 3 and 5-9

[0098] As shown in Table 3, after adding the same mass fraction of polyethylene glycol and polyacrylic acid, polyethylene glycol has a better effect on reducing viscosity and improving conductivity compared to polyacrylic acid. After introducing polyethylene glycol and polyacrylic acid into the electrolyte, both can be adsorbed on the surface of the methanesulfonic acid-vanadium complex particles, forming a coating layer. Through steric hindrance, the polymer molecular chains act as a physical barrier around the complex. When the complex approaches, these barriers generate repulsive forces, preventing them from agglomerating and precipitating again. Furthermore, the polymer molecular chains can also form a solvation layer with the solvent, allowing the coated complex particles to better compatibility with the electrolyte, further reducing the tendency to agglomerate. However, polyacrylic acid is an anionic polyelectrolyte; after adsorption, it can provide steric hindrance and also generate electrostatic repulsion due to its negative charge, potentially introducing electrostatic interference that affects the normal migration of vanadium ions and may also attract potassium ions in the system. Polyethylene glycol (PEG) is a nonionic polymer. After adsorption, it only provides pure steric hindrance. It does not introduce additional charge and does not interfere with the electrolyte's own electric field and ion migration, effectively preventing the aggregation of complexes. The addition of polyvinylpyrrolidone (PVP), polyacrylamide (PAF), and polystyrene sulfonic acid competitively disrupts the "association network" induced by potassium methanesulfonate in the electrolyte, causing the network to dissociate and the macroscopic viscosity to decrease. However, these long polymer chains also occupy solution volume, forcing ion migration paths to become longer, free water to be bound, and some conductive ions to be adsorbed or form ion pairs, thereby reducing the effective carrier concentration and mobility, ultimately leading to a decrease in conductivity.

[0099] 4. The conductivity and viscosity of the electrolytes in Examples 3, 5, and 10-14 were tested and compared. The specific results are shown in Table 4: Table 4 Comparison of viscosity and conductivity in Examples 3, 5, and 10-14

[0100] As shown in Table 4, with the gradual increase of polyethylene glycol mass fraction, viscosity first gradually decreases and then increases, while conductivity gradually increases and then decreases. When the electrolyte contains an appropriate amount of polyethylene glycol, it effectively disperses the methanesulfonate-vanadium ion complex through steric hindrance stabilization, breaking down agglomerates, and simultaneously exerts a plasticizing / lubricating effect to weaken the solvent hydrogen bond network. This reduces the hydrodynamic radius and internal friction of the solution and releases bound charge carriers, thereby reducing viscosity and increasing conductivity. However, with further increases in concentration, excess polyethylene glycol molecular chains become entangled, forming a dynamic physical network that increases flow resistance; at the same time, it generates a volume exclusion effect, hindering ion migration, which in turn leads to a rebound in viscosity and a decrease in conductivity.

[0101] 5. The battery performance of Examples 3, 5, and 6-9 was compared and the results are shown in Table 5. Table 5. Comparison of battery performance in the tenth cycle for Examples 3, 5, and 6-9.

[0102] As shown in Table 5, the addition of polyethylene glycol and polyacrylic acid effectively disperses the methanesulfonic acid-vanadium complex, reduces viscosity, and promotes ion dissociation and provides additional proton conduction pathways through flexible ether chains or carboxylic acid groups, thereby improving conductivity. Therefore, the coulombic efficiency, voltage efficiency, and energy efficiency of the battery are all improved. Among them, polyethylene glycol has the best overall effect due to its more flexible molecular chains, minimal hindrance to ion migration, and improved electrode wettability. While polyvinylpyrrolidone, polyacrylamide, and polystyrene sulfonic acid also reduce viscosity, their large molecular chains severely hinder ion transport, bind free water, or adsorb vanadium ions, leading to decreased conductivity, intensified concentration polarization, and reduced battery performance.

[0103] 6. The battery performance of Examples 3, 5, and 10-14 was compared and the results are shown in Table 6. Table 6. Comparison of 7-11 tenth cycle battery performance for Examples 3, 5, and 10-14

[0104] As can be seen from Table 6, the introduction of potassium methanesulfonate and polyethylene glycol improves the performance of the electrolyte, resulting in improved coulombic efficiency, voltage efficiency, and energy efficiency of the battery. This may be because the action of multiple groups inhibits the occurrence of side reactions such as hydrogen evolution, reduces the ineffective loss of charge, and the decrease in viscosity accelerates the mass transfer rate of ions in the porous electrode, while the increase in conductivity significantly reduces the ohmic internal resistance.

[0105] 7. The electrolyte utilization rates of the batteries in Examples 3, 5, and 10-14 were compared and the results are shown in Table 7. Table 7 Comparison of electrolyte utilization rates in Examples 3, 5, and 10-14

[0106] As can be seen from Table 7, the introduction of potassium methanesulfonate and polyethylene glycol improves the performance of the electrolyte, significantly enhancing the electrolyte utilization rate of the battery. In addition, it helps stabilize high-valence vanadium ions, inhibiting their precipitation at high concentrations, and allows the battery to operate safely at a higher state of charge by suppressing the hydrogen evolution reaction.

[0107] 8. The battery capacity retention rates of Examples 3, 5, and 10-14 were compared and the results are shown in Table 8. Table 8. Comparison of capacity retention rates of batteries from Examples 3, 5, and 10-14 after 200 cycles.

[0108] As shown in Table 8, the introduction of potassium methanesulfonate and polyethylene glycol enhanced the chemical and physical stability of the electrolyte, resulting in a significant improvement in battery capacity retention. This is likely due to the alteration of the solvation structure of vanadium ions and the prevention of vanadium complex aggregation, effectively suppressing the precipitation of pentavalent vanadium ions and slowing down the loss of active material during long-term cycling, thus reducing the rate of capacity decay.

[0109] The embodiments described above merely illustrate specific implementation methods of this application, and while the descriptions are detailed, they should not be construed as limiting the scope of protection of this application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the technical solution of this application, and these modifications and improvements all fall within the scope of protection of this application.

[0110] This background section is provided to generally present the context of the invention. The work of the currently named inventors, the work to the extent described in this background section, and aspects of this section that did not constitute prior art at the time of application are neither expressly nor impliedly acknowledged as prior art to the invention.

Claims

1. A vanadium redox flow battery electrolyte, characterized in that: It consists of a basic electrolyte, primary additives, and secondary additives; The basic electrolyte contains vanadium ions, sulfate ions and hydrogen ions. During the charging and discharging process of the vanadium redox flow battery, the vanadium ions in the positive electrode electrolyte are tetravalent and pentavalent, and the vanadium ions in the negative electrode electrolyte are divalent and trivalent. The primary additive is methanesulfonic acid or potassium methanesulfonate; The secondary additive is at least one of polyethylene glycol, polyacrylic acid, polyvinylpyrrolidone, polyacrylamide, and polystyrene sulfonic acid; The mass fraction ratio of the secondary additive to the primary additive is: 0.002% ≤ w(secondary additive) / w(primary additive) ≤ 60%.

2. The all-vanadium redox flow battery electrolyte according to claim 1, characterized in that: When the primary additive is methanesulfonic acid, its molar concentration in the electrolyte ranges from 0.001 M. 0.1M; when the primary additive is potassium methanesulfonate, its molar concentration in the electrolyte ranges from 0.001M. 0.1 M.

3. The all-vanadium redox flow battery electrolyte according to claim 1, characterized in that: The secondary additive constitutes 0.005% of the electrolyte by mass. 1.5%.

4. The vanadium redox flow battery electrolyte according to claim 1, characterized in that: The total molar concentration of vanadium ions in the basic electrolyte is 1.5 M. 2.4M, the molar concentration of sulfate ions is 2.2M. 5M, the molar concentration of hydrogen ions is 2.2M. 10M.

5. The all-vanadium redox flow battery electrolyte according to claim 1, characterized in that: The molecular weight of the polyethylene glycol is 400. 1500, the molecular weight of the polyacrylic acid is 800. 4000, wherein the molecular weight of the polyvinylpyrrolidone is 500-100000, the molecular weight of the polyacrylamide is 500-600000, and the molecular weight of the polystyrene sulfonic acid is 600-500000.

6. The all-vanadium redox flow battery electrolyte according to claim 1, characterized in that: When the primary additive is methanesulfonic acid, 0.025≤c(CH3SO3H) / c(V)≤1.5625; when the primary additive is potassium methanesulfonate, 0.025≤c(CH3SO3K) / c(V)≤1.5625.

7. The all-vanadium redox flow battery electrolyte according to claim 1, characterized in that: When the primary additive is methanesulfonic acid, 0.001% ≤ w(secondary additive) / w(CH3SO3H) ≤ 80%; when the primary additive is potassium methanesulfonate, 0.002% ≤ w(secondary additive) / w(CH3SO3K) ≤ 60%.

8. A vanadium redox flow battery, characterized in that: The vanadium redox flow battery electrolyte as described in any one of claims 1-8 is used.

9. A vanadium redox flow battery, comprising a positive electrode, a negative electrode, a separator, and a storage tank and piping system for storing and circulating electrolyte, characterized in that: The electrolytes used for both the positive and negative electrodes are all vanadium redox flow battery electrolytes as described in any one of claims 1-8.

10. The application of the all-vanadium redox flow battery electrolyte as described in any one of claims 1-8 in effectively preventing the aggregation of methanesulfonic acid-vanadium complex during battery operation, thereby improving the overall performance and service life of the battery.

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