Similar mixed redox electrolyte and aqueous organic flow battery

Abstract

The invention discloses a similar mixed redox electrolyte and an aqueous organic flow battery, and belongs to the technical field of organic flow batteries. The similar mixed redox electrolyte can be used for a positive electrode or a negative electrode, at least two cyclic nitroxide free radical active substances are introduced into the positive electrode electrolyte, and at least two viologen active substances are introduced into the negative electrode electrolyte. Derivative molecules with different substituent groups or bridging atoms but the same type are introduced into a positive electrolyte and a negative electrolyte respectively, and the same charge groups or charged atoms are carried in the substituent groups, so that the molecular structure is stabilized by increasing the intermolecular distance or weak interaction of hydrogen bonds and the like through intermolecular electrostatic repulsive force; the distribution state of molecules in the solution is regulated and controlled, the molecular aggregation behavior is reduced, and the battery capacity and the cycling stability are improved. The introduction of the charged active substance can enhance the rate capability of the battery, is beneficial to the realization of higher power density, and provides a new idea for the design and application of the high-performance aqueous organic flow battery.

Description

Technical Field

[0001] The present invention belongs to the technical field of large-scale energy storage, and in particular relates to a similar mixed redox electrolyte and an aqueous organic liquid flow battery. Background Art

[0002] Driven by the energy revolution, it has become an urgent need to develop clean energy such as wind energy, tidal energy, and solar energy to achieve sustainable transformation of the energy system. However, due to the constraints of natural conditions, renewable energy has significant intermittency and instability, which has an impact on the operation of the power grid. Therefore, it is crucial to develop new energy storage technologies to achieve grid-connected energy consumption and improve energy utilization efficiency. Liquid flow batteries, with their characteristics of decoupling energy and power, are highly consistent with the needs of large-scale energy storage technology. Among them, neutral aqueous liquid flow batteries have shown broad prospects for large-scale energy storage applications with their unique advantages such as high safety, structural design flexibility, rapid kinetic response, and green environmental protection.

[0003] At present, neutral aqueous organic flow batteries often use cyclic nitroxide free radicals as positive electrolytes and viologens as negative electrolytes. Among them, cyclic nitroxide free radicals have the advantages of high redox potential, excellent redox reversibility, environmental friendliness, and easy synthesis and optimization; viologens have the characteristics of multi-step electron transfer, low redox potential and excellent solubility. Both are widely used in neutral aqueous organic flow batteries. However, cyclic nitroxide free radicals and viologens themselves have intermolecular aggregation. Specifically, cyclic nitroxide free radicals will generate inactive hydroxylamines during the redox process, in which the hydrogen atoms interact with the oxygen atoms on other molecules through hydrogen bonds to form a dimer structure, which leads to a decrease in the number of redox active molecules in the electrolyte; in the single-electron reduced state, viologen molecules have a decrease in the number of active reaction molecules due to the attraction between the intermolecular negatively charged free radicals and the positive charge on the quaternary ammonium ion, and the conjugation of the intermolecular benzene ring promotes the occurrence of polymerization, which is manifested as a decrease in battery capacity and cycle stability. The main method at present is to graft charged substituent groups onto the parent molecule through molecular modification, and use the mutual repulsion between groups of the same charge to reduce molecular aggregation, thereby improving battery capacity and cycle stability. However, the molecular modification method often cannot take into account the advantages of all aspects, and usually has a long cycle, high cost and complex process. Summary of the invention

[0004] The purpose of the present invention is to overcome the shortcomings of the above-mentioned prior art and provide a similar mixed redox electrolyte and aqueous organic liquid flow battery to solve the problems of reduced battery capacity and poor cycle stability caused by aggregation of cyclic nitroxide free radicals and viologen molecules in the prior art.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions: A homogeneous mixed redox electrolyte comprises a redox active substance and a supporting electrolyte, wherein the redox active substance is composed of at least two active substances, and the two active substances include an electrically neutral active substance and a charged active substance; When the mixed redox electrolyte of the same type is the positive electrode electrolyte, the active substances are all cyclic nitroxide free radical active substances; When the mixed redox electrolyte of the same type is the negative electrode electrolyte, the active substances are all viologen active substances.

[0006] A further improvement of the present invention is: Preferably, when the mixed redox electrolyte of the same type is the positive electrode electrolyte, the electrically neutral active substance is a cyclic nitroxide free radical having the structural formula:

[0007] Wherein, R1 is a hydrogen atom, a hydroxyl group, an amino group, an alkoxy group, a carbonyl group, a dimethylamino group or an amide group.

[0008] Preferably, when the mixed redox electrolyte is the positive electrolyte, the charged active substance is a cyclic nitroxide free radical having the structural formula:

[0009] Wherein, R2 is a substituted or unsubstituted quaternary ammonium salt, sulfonate, carboxylate or phosphate group, and the counter ion is Cl - Or Na + .

[0010] Preferably, when the mixed redox electrolyte of the same type is the negative electrode electrolyte, the electrically neutral active substance is an alkyl-substituted viologen.

[0011] Preferably, when the mixed redox electrolyte of the same type is the negative electrode electrolyte, the charged active substance is viologen, and the structural formula is:

[0012] Wherein, R3 is a substituted quaternary ammonium salt, phosphate, sulfonate or carboxylate group, and X - It is a monovalent counter ion, n is an integer between 1 and 4, and the value depends on the sum of the number of positive and negative ions in the R3 substituent and the two negative ions on the pyridine ring to meet the charge balance.

[0013] Preferably, the concentration of the cyclic nitroxide free radical active substance in the positive electrode electrolyte is 2 mM~3 M.

[0014] Preferably, the concentration of the viologen active substance in the negative electrode electrolyte is 2 mM~3 M.

[0015] Preferably, in the active material, the molar ratio of the charged active material to the electrically neutral active material is 1-10.

[0016] Preferably, the supporting electrolyte is an inorganic salt aqueous solution.

[0017] An aqueous organic liquid flow battery comprises a positive electrode electrolyte and a negative electrode electrolyte; at least one of the positive electrode electrolyte and the negative electrode electrolyte is the above-mentioned similar mixed redox electrolyte.

[0018] Compared with the prior art, the present invention has the following beneficial effects: The present invention discloses a mixed redox electrolyte of the same type, which is a positive electrode electrolyte or a negative electrode electrolyte. At least two cyclic nitrogen oxide free radical active substances are added to the positive electrode electrolyte, and at least two viologen active substances are added to the negative electrode electrolyte. These active substances are of the same type, but have different substituents or bridging atoms. The substituents contain the same type of charged groups or charged atoms, which increase the intermolecular distance through the electrostatic repulsion between molecules, or stabilize the molecular structure through weak interactions such as hydrogen bonds, thereby effectively regulating the distribution state of molecules in the solution, reducing the occurrence of molecular aggregation behavior, and significantly improving the battery capacity and cycle stability. In addition, the introduction of charged active substances in the mixed electrolyte improves the ionic conductivity of the positive and negative electrode electrolytes, thereby enhancing the rate performance of the battery, which is conducive to achieving high power density. Compared with the chemical modification modification method, the present invention has the advantages of simple method and easy operation, is suitable for batch preparation of high-performance electrolytes, and provides new ideas for the practical application of liquid flow battery performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 cyclic voltammetry curves of the mixed cathode electrolyte in Example 1 of the present invention at different scan rates, the scan rates being 25 mV / s, 64 mV / s, 100 mV / s, 225 mV / s, 400 mV / s and 625 mV / s; Figure 2 is a curve showing a change in the redox peak current of the mixed positive electrode electrolyte as a function of the square root of the scanning speed in Example 1 of the present invention; Figure 3 The mixed positive electrode electrolyte full battery in Example 2 of the present invention is 30 mA / cm 2 Constant current charge and discharge 100 cycles performance.

[0020] Figure 4 cyclic voltammetry curves of the mixed cathode electrolyte in Example 3 of the present invention at different scan rates, the scan rates being 25 mV / s, 64 mV / s, 100 mV / s, 225 mV / s, 400 mV / s and 625 mV / s; Figure 5 is a curve showing a change in the redox peak current of the mixed positive electrode electrolyte as a function of the square root of the scanning speed in Example 3 of the present invention; Figure 6 The mixed positive electrode electrolyte in Example 4 of the present invention is 30 mA / cm 2 100 cycles of constant current at current density; Figure 7 cyclic voltammetry curves of the mixed negative electrode electrolyte in Example 5 of the present invention at different scan rates, the scan rates being 25 mV / s, 64 mV / s, 100 mV / s, 225 mV / s, 400 mV / s and 625 mV / s; Figure 8 is a curve showing a change in the redox peak current of the mixed negative electrode electrolyte as a function of the square root of the scanning speed in Example 5 of the present invention; Fig. 9 The mixed negative electrode electrolyte full battery in Example 6 of the present invention is 30 mA / cm 2 100 cycles of current density; Fig.10 The comparative electrolyte of the present invention is a full battery at 30 mA / cm 2 Constant current charge and discharge 100 cycles performance. DETAILED DESCRIPTION

[0021] The present invention is further described in detail below in conjunction with the accompanying drawings: In order to enable those skilled in the art to understand the characteristics and effects of the present invention, the following is a general description and definition of the terms and expressions mentioned in the specification and claims. Unless otherwise specified, all technical and scientific terms used in the text are the common meanings understood by those skilled in the art for the present invention. In the event of a conflict, the definition in this specification shall prevail.

[0022] In this document, unless otherwise specified, “includes,” “including,” “contains,” “has,” or similar terms cover the meanings of “consisting of” and “mainly consisting of,” for example, “A includes a” covers the meanings of “A includes a and other” and “A only includes a.”

[0023] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall within the scope limited by the appended claims of the application equally.

[0024] The following examples use conventional instruments and equipment in the art. The experimental methods in the following examples where specific conditions are not specified are usually carried out under conventional conditions or under conditions recommended by the manufacturer. The various raw materials used in the following examples are conventional commercial products unless otherwise specified, and their specifications are conventional specifications in the art. In the specification of the present invention and the following examples, unless otherwise specified, "%" means weight percentage, "part" means weight part, and ratio means weight ratio.

[0025] The first aspect of the present invention discloses the preparation of a mixed redox electrolyte of the same type, wherein the mixed redox electrolyte is prepared as a positive electrode electrolyte or a negative electrode electrolyte; each type of mixed electrolyte includes an active substance and a supporting electrolyte; there are at least two active substances, one of which is an electrically neutral active substance and the other is a charged active substance. When the mixed redox electrolyte of the same type is a positive electrode electrolyte, both active substances are cyclic nitroxide free radicals; when the mixed redox electrolyte of the same type is a negative electrode electrolyte, both active substances are viologens. The present invention uses simple physical means to mix electrolytes of the same type, aiming to improve the aggregation degree of the system and improve the battery capacity and stability.

[0026] Specifically, the active substance in the mixed positive electrode electrolyte is a cyclic nitroxide free radical active substance, and the structural formula is as follows:

[0027] III R1 in formula I is uncharged, and the cyclic nitroxide free radicals of formula I are electrically neutral active substances; R2 in formula II is charged, and the cyclic nitroxide free radicals of formula II are charged active substances; R1 in the electrically neutral active substance is a hydrogen atom, hydroxyl, amino, alkoxy, carbonyl, dimethylamino or amide. R2 of the charged active substance is a substituted or unsubstituted quaternary ammonium salt, sulfonate, carboxylate or phosphate group, and the counter ion is Cl - Or Na + .

[0028] The active substance in the negative electrode electrolyte is a viologen-type substance, and the general formula of its active structural unit is shown in the figure:

[0029] III Among them, X - is a monovalent counterion; in formula III, if R3 is uncharged, it is an electrically neutral active substance; if R3 is charged, it is a charged active substance. Specifically, the uncharged active substance R3 is an alkyl-substituted viologen, and the charged active substance R3 is a substituted quaternary ammonium salt, phosphate, sulfonate or carboxylate group. - Cl - Or Na+ , n is an integer between 1 and 4, and its value depends on the sum of the number of positive and negative ions in the R3 substituent and the two negative ions on the pyridine ring to satisfy the charge balance.

[0030] By adopting the above scheme, by mixing cyclic nitroxide free radicals and their derivative molecules substituted with atoms of the same charge group, the distance between molecules is increased by electrostatic repulsion between molecules or weak interactions such as hydrogen bonds stabilize the molecular structure, the distribution state of molecules in the solution is regulated, and the aggregation between molecules is inhibited. In addition, the addition of charged cyclic nitroxide free radical active substances can improve the rate performance of the battery and increase the power density of the battery.

[0031] As a preferred embodiment, the electrically neutral active material in the mixed electrolyte cyclic nitroxide free radical is any one of the following structural formulas:

[0032] As a preferred embodiment, the charged active substance in the mixed electrolyte cyclic nitroxide free radical is any one of the following structural formulas:

[0033] As a preferred embodiment, the molar ratio of the charged active substance to the neutral active substance in the cyclic nitroxide free radicals is 1-10.

[0034] As a preferred embodiment, the mixed electrolyte contains two or more types of active substances in the cyclic nitroxide free radical positive electrode electrolyte.

[0035] By adopting the above scheme, the viologen negative electrode is mixed, and the weak interaction forces such as Coulomb repulsion or hydrogen bonding between viologen molecules with grafted charged substituents are utilized to regulate the state of the molecules in the solution, reduce the aggregation behavior between molecules, and reduce the possibility of forming low-activity aggregates in the single-electron reduced state, thereby improving the cycle stability of the battery. At the same time, the mixing of charged viologen molecules can increase the ion concentration of the system and improve the rate performance of the battery.

[0036] As a preferred embodiment, the electrically neutral active substance in the mixed electrolyte viologen is methyl viologen:

[0037] As a preferred embodiment, the charged active substance in the mixed electrolyte viologen is any one of the following structural formulas:

[0038] As a preferred embodiment, the molar ratio of the charged active substance to the electrically neutral active substance in the mixed electrolyte viologen is 1-10.

[0039] As a preferred embodiment, the mixed electrolyte viologen-based negative electrode electrolyte active substances are mixed in two or more types; In the embodiment of the present invention, a potassium chloride (KCl) aqueous solution is used as a supporting electrolyte, and the concentration of the supporting electrolyte is 1 mol / L.

[0040] The present invention also discloses an aqueous organic liquid flow battery, which consists of a positive electrolyte, a positive flow field plate, a positive electrode, an ion diaphragm, a negative electrode, a negative flow field plate and a negative electrolyte; the active substance in the positive electrolyte is a mixed cyclic nitrogen oxide free radical and its derivative molecules; the active substance in the negative electrolyte is a mixed viologen and its derivative molecules; and the supporting electrolyte is a potassium chloride aqueous solution.

[0041] Preferably, when the above-mentioned mixed electrolyte full battery is used, the electrolyte electrode on the opposite side can be of any other type, such as an organic system, a zinc system, etc.

[0042] Preferably, the aqueous organic liquid flow battery uses a copper plate as a current collector, a graphite plate as a flow field plate, a carbon felt as a reaction electrode, and an ion exchange membrane between the positive electrode and the negative electrode.

[0043] The specific embodiments are: Example 1 Weigh 1.378 mg of positive electrode molecule-2 and 2.455 mg of positive electrode molecule-11, respectively, with a molar ratio of positive electrode molecule-2 to positive electrode molecule-11 of 1:1, and dissolve them in 8 mL of 1 M KCl aqueous solution to prepare a 2 mM positive electrode electrolyte. Cyclic voltammetry was performed using a three-electrode system, with a silver / silver chloride electrode as the reference electrode, a glassy carbon electrode as the working electrode, and a platinum sheet electrode as the counter electrode. The selected scan rates were 25 mV / s, 64 mV / s, 100 mV / s, 225 mV / s, 400 mV / s, and 625 mV / s, and the results were as follows: Figure 1 The cyclic voltammetry curve is shown in Figure 2. The peak redox current at different scan rates is fitted with the square root of the scan rate to obtain Figure 2 , it can be seen from the figure that at different scan rates, the peak current has a good linear fitting relationship with the scan rate, indicating that the positive electrode electrolyte molecules still have excellent redox reversibility after mixing, and the process is controlled by diffusion. At the same time, after adding the positive electrode molecule-11, there are two pairs of reversible redox peaks, indicating that the system has become a two-step two-electron transfer, and the electrolyte potential after mixing is increased, which is conducive to the construction of a high-voltage battery system.

[0044] Example 2 Weigh 51.675 mg of positive electrode molecule-2 and 92.058 mg of positive electrode molecule-11, respectively, with a molar ratio of positive electrode molecule-2 to positive electrode molecule-11 of 1:1, dissolve in 6 mL of 1 M KCl aqueous solution, stir thoroughly for 30 min to prepare 0.1 M positive electrode electrolyte. Weigh 450.3 mg of negative electrode molecule-3 and dissolve in 9 mL of 1 M KCl aqueous solution, stir thoroughly for 30 min to prepare 0.1 M negative electrode electrolyte. Bubble the prepared positive and negative electrolytes under nitrogen for 30 min to remove oxygen, and then transfer them to the glove box for testing. The above-mentioned positive electrode material electrolyte and negative electrode material electrolyte are stored in the positive and negative electrode storage tanks on both sides, respectively, and circulated with a peristaltic pump. The positive and negative electrode electrolytes circulate through the pipelines and meet on both sides of the diaphragm. The graphite felt electrodes on both sides of the diaphragm undergo redox reactions. The positive and negative electrodes are connected to the power supply or load, the circuit transfers electrons, and the diaphragm transfers anions or cations to form a loop. The battery was evaluated for cycle stability using a 30 mA / cm 2 The constant current charge and discharge test was carried out with a current density of 1.6 V to 0.9 V. Figure 3 The test results show that the battery's first coulombic efficiency is above 99%, the first-cycle discharge capacity is 14.3 mAh, and after 100 cycles, the discharge capacity is 14 mAh, the capacity decay rate is 0.021% / cycle, and the coulombic efficiency remains above 99.5% on average, indicating that the system has excellent cycle stability.

[0045] Example 3 Weigh 1.102 mg of positive electrode molecule-2 and 3.566 mg of positive electrode molecule-12, respectively, with a molar ratio of positive electrode molecule-2 to positive electrode molecule-12 of 2:3, and dissolve them in 8 mL of 1 M KCl aqueous solution to prepare a 2 mM positive electrode electrolyte. Cyclic voltammetry was performed using a three-electrode system, with a silver / silver chloride electrode as the reference electrode, a glassy carbon electrode as the working electrode, and a platinum sheet electrode as the counter electrode. The selected scan rates were 25 mV / s, 64 mV / s, 100 mV / s, 225 mV / s, 400 mV / s, and 625 mV / s, and the results were as follows: Figure 4 The cyclic voltammetry curve is shown in Figure 2. The peak redox current at different scan rates is fitted with the square root of the scan rate to obtain Figure 5 , it can be seen from the figure that at different scan rates, the peak current has a good linear fitting relationship with the scan rate, indicating that the electrolyte molecules still have excellent redox reversibility after mixing, and the process is controlled by diffusion. At the same time, after adding the positive electrode molecule-12, there are two pairs of reversible redox peaks, indicating that the system has become a two-step two-electron transfer, and the system potential has increased, which is conducive to the construction of a high-voltage battery system.

[0046] Example 4 Weigh 41.34 mg of positive electrode molecule-2 and 133.708 mg of positive electrode molecule-12, respectively, with a molar ratio of positive electrode molecule-2 to positive electrode molecule-12 of 2:3, dissolve in 6 mL of 1 M KCl aqueous solution, stir thoroughly for 30 min to prepare 0.1 M positive electrode electrolyte, weigh 450.3 mg of negative electrode molecule-3 and dissolve in 9 mL of 1 M KCl aqueous solution, stir thoroughly for 30 min to prepare 0.1 M negative electrode electrolyte. The prepared positive and negative electrolytes were bubbled under nitrogen for 30 min to remove oxygen, and then transferred to the glove box for testing. The above-mentioned positive electrode material electrolyte and negative electrode material electrolyte were stored in the positive and negative electrode storage tanks on both sides, respectively, and circulated with a peristaltic pump. The positive and negative electrode electrolytes circulate through the pipelines and meet on both sides of the diaphragm. The graphite felt electrodes on both sides of the diaphragm undergo redox reactions. The positive and negative electrodes are connected to the power supply or load, the circuit transfers electrons, and the diaphragm transfers anions or cations to form a loop. The battery was evaluated for cycle stability using a 30 mA / cm 2 The constant current charge and discharge test was carried out with a current density of 1.6 V to 0.9 V. Figure 6 The test results show that the first coulombic efficiency is above 99%, the first cycle discharge capacity is 13.3 mAh, and after 100 cycles, the discharge capacity is 13.1 mAh, with a capacity decay rate of 0.015% / cycle, indicating that the system has excellent cycle stability.

[0047] Example 5 Weigh 2.057 mg of negative electrode molecule-1 and 4.003 mg of negative electrode molecule-3 respectively, the molar ratio of negative electrode molecule-1 to negative electrode molecule-3 is 1:1, and dissolve them in 8 mL of 1 M KCl aqueous solution to prepare 2 mM negative electrode electrolyte. Bubble the solution under nitrogen for 30 min to remove oxygen. Cyclic voltammetry was performed using a three-electrode system. The reference electrode used was a silver / silver chloride electrode, the working electrode was a glassy carbon electrode, and the counter electrode was a platinum sheet electrode. The selected scan rates were 25 mV / s, 64 mV / s, 100 mV / s, 225 mV / s, 400 mV / s and 625 mV / s, and the results were Figure 7 The cyclic voltammetry curve is shown in Figure 2. The peak redox current at different scan rates is fitted with the square root of the scan rate to obtain Figure 8 ,It can be seen from the figure that at different scan rates, the peak current has a good linear fitting relationship with the scan rate, indicating that the electrolyte molecules still have their own excellent redox reversibility after mixing, and the process is controlled by diffusion.

[0048] Example 6 Weigh 77.148 mg of negative electrode molecule-1 and 150.111 mg of negative electrode molecule-3, respectively, with a molar ratio of negative electrode molecule-1 to negative electrode molecule-3 of 1:1, dissolve in 6 mL of 1 M KCl aqueous solution, stir thoroughly for 30 min to prepare 0.1 M negative electrode electrolyte. Weigh 224.82 mg of positive electrode molecule-10 and dissolve in 9 mL of 1 M KCl aqueous solution, stir thoroughly for 30 min to prepare 0.1 M negative electrode electrolyte. Bubble the prepared positive and negative electrolytes under nitrogen for 30 min to remove oxygen, and then transfer them to the glove box for testing. The above-mentioned positive electrode material electrolyte and negative electrode material electrolyte are stored in the positive and negative electrode storage tanks on both sides, respectively, and circulated with a peristaltic pump. The positive and negative electrode electrolytes circulate through the pipelines and meet on both sides of the diaphragm. The graphite felt electrodes on both sides of the diaphragm undergo redox reactions. The positive and negative electrodes are connected to the power supply or load, the circuit transfers electrons, and the diaphragm transfers anions or cations to form a loop. The battery was evaluated for cycle stability using a 30 mA / cm 2 The constant current charge and discharge test was carried out with a current density of 1.6 V to 0.8 V as the cut-off voltage. Fig. 9 The test results show that the battery's first coulombic efficiency is above 99%, the first-cycle discharge capacity is 10.6 mAh, and after 100 cycles, the discharge capacity is 9.6 mAh, with a capacity decay rate of 0.094% / cycle, indicating that the system has excellent cycle stability.

[0049] Comparative Example 1 Weigh 103.35 mg of positive electrode molecule-2 and dissolve it in 6 mL of 1 M KCl aqueous solution, stir it thoroughly for 30 minutes to prepare a 0.1 M positive electrode electrolyte. Weigh 154.296 mg of negative electrode molecule-1 and dissolve it in 6 mL of 1 M KCl aqueous solution, stir it thoroughly for 30 minutes to prepare a 0.1 M negative electrode electrolyte. Bubble the prepared positive and negative electrolytes under nitrogen for 30 minutes to remove oxygen, and then transfer them to a glove box for testing. The above-mentioned positive electrode material electrolyte and negative electrode material electrolyte are stored in the positive and negative electrode storage tanks on both sides, respectively, and circulated with a peristaltic pump. The positive and negative electrode material electrolytes circulate separately through the pipeline and intersect on both sides of the diaphragm. Redox reactions occur at the graphite felt electrodes on both sides of the diaphragm. The positive and negative electrodes are connected to the power supply or load, the circuit transfers electrons, and the diaphragm transfers anions or cations to form a loop. The cycle stability performance of the battery was evaluated using 30 mA / cm 2 The constant current charge and discharge test was carried out with a current density of 1.6 V to 0.8 V as the cut-off voltage. Fig.10The test results show that the first coulombic efficiency is above 98%, the first cycle discharge capacity is 12.4 mAh, and after 100 cycles, the discharge capacity is 9.3 mAh, with a capacity decay rate of 0.25% / cycle, indicating that the comparative example has poor cycle stability.

[0050] Example 7 Weigh 0.345 g of positive electrode molecule-2 and 3.069 g of positive electrode molecule-11, respectively, with a molar ratio of positive electrode molecule-2 to positive electrode molecule-11 of 1:5, dissolve in 6 mL of 1 M KCl aqueous solution, stir thoroughly for 30 min to prepare a 2 M positive electrode electrolyte. Weigh 9.007 g of negative electrode molecule-3 and dissolve in 9 mL of 1 M KCl aqueous solution, stir thoroughly for 30 min to prepare a 2 M negative electrode electrolyte. The prepared positive and negative electrolytes were bubbled under nitrogen for 30 min to remove oxygen, and then transferred to a glove box for testing.

[0051] Example 8 Weigh 0.094 g of positive electrode molecule-2 and 2.026 g of positive electrode molecule-12, respectively, with a molar ratio of positive electrode molecule-2 to positive electrode molecule-12 of 1:10, dissolve in 6 mL of 1 M KCl aqueous solution, stir thoroughly for 30 min to prepare a 1 M positive electrode electrolyte. Weigh 4.503 g of negative electrode molecule-3 and dissolve in 9 mL of 1 M KCl aqueous solution, stir thoroughly for 30 min to prepare a 1 M negative electrode electrolyte. The prepared positive and negative electrolytes were bubbled under nitrogen for 30 min to remove oxygen, and then transferred to a glove box for testing.

[0052] Example 9 Weigh 0.387 g of positive electrode molecule-2 and 5.850 g of positive electrode molecule-12, respectively, with a molar ratio of positive electrode molecule-2 to positive electrode molecule-12 of 1:7, dissolve in 6 mL of 1 M KCl aqueous solution, stir well for 30 min to prepare a 3 M positive electrode electrolyte. Weigh 13.51 g of negative electrode molecule-3 and dissolve in 9 mL of 1 M KCl aqueous solution, stir well for 30 min to prepare a 3 M negative electrode electrolyte. The prepared positive and negative electrolytes were bubbled under nitrogen for 30 min to remove oxygen, and then transferred to a glove box for testing.

[0053] Example 10 Weigh 0.210 g of negative electrode molecule-1 and 4.094 g of negative electrode molecule-3, respectively, with a molar ratio of negative electrode molecule-1 to negative electrode molecule-3 of 1:10, dissolve in 6 mL of 1 M KCl aqueous solution, stir thoroughly for 30 min to prepare a 1.5 M negative electrode electrolyte. Weigh 3.372 g of positive electrode molecule-10 and dissolve in 9 mL of 1 M KCl aqueous solution, stir thoroughly for 30 min to prepare a 1.5 M negative electrode electrolyte. The prepared positive and negative electrolytes were bubbled under nitrogen for 30 min to remove oxygen, and then transferred to a glove box for testing.

[0054] Embodiment 11 Weigh 0.514 g of negative electrode molecule-1 and 5.324 g of negative electrode molecule-2, respectively, with a molar ratio of negative electrode molecule-1 to negative electrode molecule-2 of 1:5, dissolve in 6 mL of 1 M KCl aqueous solution, stir thoroughly for 30 min to prepare 2 M negative electrode electrolyte. Weigh 4.496 g of positive electrode molecule-10 and dissolve in 9 mL of 1 M KCl aqueous solution, stir thoroughly for 30 min to prepare 2 M negative electrode electrolyte. The prepared positive and negative electrolytes were bubbled under nitrogen for 30 min to remove oxygen, and then transferred to the glove box for testing.

[0055] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A homogeneous mixed redox electrolyte, characterized in that: It includes a redox active substance and a supporting electrolyte, wherein the redox active substance is composed of at least two active substances, and the two active substances include an electrically neutral active substance and a charged active substance; When the mixed redox electrolyte of the same type is the positive electrode electrolyte, the active substances are all cyclic nitroxide free radical substances; When the mixed redox electrolyte of the same type is the negative electrode electrolyte, the active substances are all viologen substances.

2. A homogeneous mixed redox electrolyte according to claim 1, characterized in that: When the mixed redox electrolyte of the same type is the positive electrolyte, the electrically neutral active substance is a cyclic nitroxide free radical, and the structural formula is: Wherein, R1 is a hydrogen atom, a hydroxyl group, an amino group, an alkoxy group, a carbonyl group, a dimethylamino group or an amide group.

3. A homogeneous mixed redox electrolyte according to claim 1, characterized in that: When the mixed redox electrolyte of the same type is the positive electrolyte, the charged active substance is a cyclic nitroxide free radical, and the structural formula is: Wherein, R2 is a substituted or unsubstituted quaternary ammonium salt, sulfonate, carboxylate or phosphate group, and the counter ion is Cl - Or Na + .

4. A homogeneous mixed redox electrolyte according to claim 1, characterized in that: When the mixed redox electrolyte of the same type is the negative electrode electrolyte, the electrically neutral active substance is an alkyl-substituted viologen.

5. A homogeneous mixed redox electrolyte according to claim 1, characterized in that: When the mixed redox electrolyte of the same type is the negative electrode electrolyte, the charged active substance is viologen, and its structural formula is: Wherein, R3 is a substituted quaternary ammonium salt, phosphate, sulfonate or carboxylate group, and X - It is a monovalent counter ion, and n is an integer of 1-4.

6. A homogeneous mixed redox electrolyte according to claim 1, characterized in that: The concentration of the cyclic nitroxide free radical substance in the positive electrode electrolyte is 2 mM~3 M.

7. A homogeneous mixed redox electrolyte according to claim 1, characterized in that: The concentration of the viologen substance in the negative electrode electrolyte is 2 mM~3 M.

8. A homogeneous mixed redox electrolyte according to claim 1, characterized in that: In the active material, the molar ratio of the charged active material to the electrically neutral active material is 1-10.

9. A homogeneous mixed redox electrolyte according to claim 1, characterized in that: The supporting electrolyte is an inorganic salt aqueous solution.

10. An aqueous organic liquid flow battery, characterized in that: The aqueous organic liquid flow battery comprises a positive electrode electrolyte and a negative electrode electrolyte; at least one of the positive electrode electrolyte and the negative electrode electrolyte is the same type of mixed redox electrolyte as described in claim 1.

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