Negative electrode electrolyte in aqueous organic flow battery and aqueous organic flow battery

Abstract

The invention discloses a negative electrode electrolyte in an aqueous organic flow battery and the aqueous organic flow battery, and belongs to the technical field of aqueous flow batteries. According to the invention, one or more inorganic cations are introduced into the negative electrode active material system of the neutral aqueous organic flow battery to serve as the functional additive, so that the overall conductivity of the electrolyte and the cycling stability of the battery in the operation process are remarkably improved. The inorganic cation addition strategy not only enhances the migration speed of ions in an electric field, but also effectively inhibits possible side reactions in the charge-discharge process, and reduces the irreversible loss of active substances, thereby significantly prolonging the cycle life and improving the stability of the battery. The cathode electrolyte optimization method provided by the invention provides a brand new design thought and a feasible solution for constructing the aqueous organic flow battery with high performance and long service life, and has important application value and practical engineering significance.

Description

Technical Field

[0001] The present invention belongs to the technical field of aqueous organic liquid flow batteries, and in particular relates to a negative electrode electrolyte in an aqueous organic liquid flow battery and an aqueous organic liquid flow battery. Background Art

[0002] Driven by the goals of "carbon peak and carbon neutrality", new energy sources represented by photovoltaics and wind power will gradually become the main body of the energy structure. However, these new energy power generation methods are affected by natural conditions and have disadvantages such as intermittency, volatility and uncontrollability, which seriously restrict the development of their large-scale application. As a new type of large-scale energy storage technology, aqueous organic liquid flow batteries use water-soluble redox organic molecules as energy storage media to achieve energy storage and release. They have the characteristics of low cost, high safety and decoupling design of power and capacity. They are expected to solve the bottleneck problems that restrict the large-scale application of new energy technologies.

[0003] Redox-active organic molecules are key components of aqueous organic flow battery electrolytes and play a decisive role in battery performance. Generally speaking, redox-active organic molecules with conjugated structures have high carrier mobility, and the π electrons in the conjugated system can be freely transferred within the molecule, so they often have good electron transport properties. However, under the charge and discharge conditions of aqueous organic flow batteries, the charged state structure of the redox-active organic molecules is prone to side reactions such as aggregation and disproportionation due to the influence of their conjugation, electrostatics, and other weak interactions, resulting in the inactivation of the organic active molecules, thereby reducing the capacity and service life of the aqueous organic flow battery. 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 negative electrode electrolyte in an aqueous organic liquid flow battery and an aqueous organic liquid flow battery to solve the problems of poor stability of redox organic active molecules, rapid battery capacity decay and short life in the prior art.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] A negative electrode electrolyte in an aqueous organic liquid flow battery, comprising an organic active material, an inorganic cation and a supporting electrolyte solution;

[0007] The organic active substance is a redox active molecule having a conjugated structure;

[0008] The inorganic cation is any one or more of a monovalent cation, a divalent cation, a trivalent cation, a tetravalent cation and a pentavalent cation;

[0009] The supporting electrolyte solution is a water-soluble salt solution.

[0010] A further improvement of the present invention is:

[0011] Preferably, the monovalent cation is selected from potassium ions (K + ) or its hydrate, sodium ion (Na + ) or its hydrate, lithium ion (Li + ) or its hydrate, and ammonium ion (NH4 + ) or one or more of its hydrates.

[0012] Preferably, the divalent cation is selected from calcium ions (Ca 2+ ) or its hydrate, magnesium ion (Mg 2+ ) or its hydrate, and barium ions (Ba 2+ ) or one or more of its hydrates.

[0013] Preferably, the trivalent cation is selected from aluminum ions (Al 3+ ) or its hydrate, cerium ion (Ce 3+ ) or its hydrate, and iron ions (Fe 3+ ) or one or more of its hydrates.

[0014] Preferably, the tetravalent cation is a zirconium ion (Zr 4+ ) or its hydrate, wherein the pentavalent cation is a niobium ion (Nb 5+ ) or a hydrate thereof.

[0015] Preferably, the electrolyte molecule having a conjugated structure is any one of a viologen compound, an imide compound and an anthraquinone compound.

[0016] Preferably, the concentration of the inorganic cation is 0.025 to 3 mol / L.

[0017] Preferably, the concentration of the organic redox active molecules is 0.01 to 3 mol / L.

[0018] Preferably, the inorganic cations include at least two types of inorganic cations.

[0019] Preferably, the two types of inorganic cations have the same valence.

[0020] Preferably, the valence states of the two types of inorganic cations are different;

[0021] Preferably, the valence states of the two types of inorganic cations are monovalent and trivalent;

[0022] Preferably, the valence states of the two types of inorganic cations are divalent and trivalent, respectively.

[0023] Preferably, the valence of the inorganic cation is greater than or equal to trivalence.

[0024] An aqueous organic liquid flow battery comprises 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 positive electrolyte is an aqueous solution of a cyclic nitroxide free radical compound or a ferrocene compound, and the negative electrolyte is the above-mentioned negative electrolyte.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] The present invention introduces inorganic cations of varying types and valences into the electrolyte system, acting as charge carriers in the electrochemical reaction process. These cations significantly modulate the interaction between the oxidized and reduced states of the organic active molecules through electrostatic interactions, thereby altering their presence in the electrolyte. This effectively inhibits the aggregation of high-energy molecules and reduces the occurrence of side reactions such as molecular disproportionation and polymerization. This mechanism significantly enhances the chemical stability of the organic active molecules, resulting in higher capacity retention and longer cycle life during continuous charge and discharge.

[0027] In addition, compared with traditional organic molecule chemical modification strategies, such as introducing substituents or constructing covalently bonded structural modification methods, the cation addition regulation method proposed in the present invention has significant advantages such as simple operation, high regulation efficiency, good system reversibility, and low cost. It not only enhances the ion transport performance, but also effectively inhibits the side reactions that may occur during the charge and discharge process, reduces the irreversible loss of active substances, and thus significantly extends the cycle life and stability of the battery. This strategy not only effectively improves the overall performance of aqueous organic liquid flow batteries, but also has good scalability and engineering potential, is more adaptable to large-scale production needs, and is in line with the current development direction of green energy technology. In summary, the present invention realizes the effective regulation of the performance of the negative electrode electrolyte in the aqueous organic liquid flow battery by designing a reasonable inorganic cation addition method, provides a simple, efficient and sustainable development potential solution, and provides technical support for the promotion, application and industrialization of liquid flow batteries. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 The relationship curve between the capacity percentage and the number of cycles of aqueous organic liquid flow batteries based on 1,1'-dimethyl-4,4'-bipyridinium dichloride (MV) electrolyte with added magnesium chloride, calcium chloride and no ions added.

[0029] Figure 2 The relationship curves between the normalized capacity and the number of cycles of MV electrolyte-based aqueous organic liquid flow batteries with no addition, 0.025 mol / L and 0.25 mol / L magnesium chloride addition.

[0030] Figure 3The capacity-voltage curve of the MV electrolyte-based aqueous organic flow battery with the addition of potassium chloride.

[0031] Figure 4 The capacity-voltage curve of the MV electrolyte-based aqueous organic flow battery with the addition of calcium chloride.

[0032] Figure 5 The capacity-voltage curve of the MV electrolyte-based aqueous organic flow battery with magnesium chloride added.

[0033] Figure 6 Cycling performance curves of aqueous organic flow batteries with and without magnesium chloride added, 1,1'-bis[3-(trimethylammonium)propyl]-4,4'-bipyridinium tetrachloride ((NPr)2V) electrolyte.

[0034] Figure 7 The capacity-voltage curve of the (NPr) 2V electrolyte-based aqueous organic flow battery with magnesium chloride added. DETAILED DESCRIPTION

[0035] The present invention is described in further detail below with reference to the accompanying drawings:

[0036] To facilitate understanding of the features and effects of the present invention by those skilled in the art, the following provides a general description and definition of the terms and expressions used in the specification and claims. Unless otherwise indicated, all technical and scientific terms used herein have the ordinary meanings as understood by those skilled in the art regarding the present invention. In the event of conflict, the definitions in this specification shall prevail.

[0037] In this document, unless otherwise specified, “include,” “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.”

[0038] Below in conjunction with specific embodiment, further set forth the present invention.Should be understood that these embodiments are only used to illustrate the present invention and are not used in limiting the scope of the present invention.In addition, 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 equally within the scope limited by the appended claims of the application.

[0039] The following examples were prepared using conventional instruments and equipment in the art. Experimental methods in the following examples, where specific conditions are not specified, were generally performed under conventional conditions or according to the conditions recommended by the manufacturer. The various raw materials used in the following examples, unless otherwise specified, were conventional commercially available products, with specifications conventional in the art. In the present specification and the following examples, unless otherwise specified, "%" indicates percentage by weight, "part" indicates parts by weight, and "ratio" indicates weight ratio.

[0040] For aqueous organic liquid flow batteries, electrolytes with conjugated structures are often added to the negative electrode electrolyte as redox active substances. The conjugated electrolyte molecules have a conjugated π bond structure, that is, two or more double bonds (or triple bonds) are connected by a single bond, which makes the range of electron movement larger and forms a continuous electron cloud, so it has a higher carrier mobility; however, as the battery operates, the conjugated electrolyte molecules are prone to aggregation, resulting in the inactivation of the organic active substance, thereby reducing the capacity and service life of the aqueous organic liquid flow battery.

[0041] In order to solve the above problems, the first aspect of the present invention discloses a negative electrode electrolyte in an aqueous organic liquid flow battery, which electrolyte includes an organic active substance, an inorganic cation and a supporting electrolyte solution; wherein the organic active substance is a redox active molecule with a conjugated structure; the inorganic cation is selected from any one or more of monovalent cations, divalent cations, trivalent cations, tetravalent cations and pentavalent cations; and the supporting electrolyte solution is a water-soluble salt solution.

[0042] The present invention introduces inorganic cations into the negative electrode electrolyte of the aqueous organic liquid flow battery. The inorganic cations act as charge carriers and influence the interaction between the charge states in the electrolyte molecules through electrostatic effects. When adding the above-mentioned inorganic cations to the negative electrode electrolyte, any one or a mixture of several of them is selected. The added inorganic cations effectively regulate the spatial configuration of the negative electrode electrolyte molecules with a conjugated structure, forming complexes or ion pairs with them, and inhibiting the aggregation or precipitation of the negative electrode electrolyte molecules. The inorganic cations can also form solvation shells with water molecules, reducing the activity of the water molecules, thereby reducing the occurrence of water electrolysis side reactions, improving the stability of the negative electrode electrolyte, significantly improving the overall conductivity of the electrolyte and the coulombic efficiency during battery operation, and inhibiting battery capacity decay.

[0043] In some embodiments of the present invention, the monovalent cation is potassium ion (K + ) or its hydrate, sodium ion (Na + ) or its hydrate, lithium ion (Li + ) or its hydrate, ammonium ion (NH4 + ) or its hydrate; the divalent cation is calcium ion (Ca 2+) or its hydrate, magnesium ion (Mg 2+ ) or its hydrate, barium ion (Ba 2+ ) or its hydrate; the trivalent cation is aluminum ion (Al 3 + ) or its hydrate, cerium ion (Ce 3+ ) or its hydrate, iron ion (Fe 3+ ) or its hydrate; the tetravalent cation is zirconium ion (Zr 4+ ) or its hydrate, the pentavalent cation is niobium ion (Nb 5+ ) or a hydrate thereof.

[0044] For example, the substances corresponding to the cations can be: KCl, K2SO4, K2CO3, K3PO4, CH3COOK, NaCl, Na2SO4, N a2 CO3, Na3PO4, CH3COONa, LiCl, Li2SO4, Li2CO3, Li3PO4, CH3COOLi, NH4Cl, (NH4)2SO4, (NH4)2CO3, (NH4)3PO4, CH3COONH4, CaCl2 , CaSO4, CaCO3, Ca3(PO4)2, Ca(CH3COO)2, MgCl2, MgSO4, MgCO3, Mg3(PO4)2, Mg(CH3COO)2, BaCl2, Ba3(PO4)2, Ba(CH3COO)2, AlCl 3. Al2(SO4)3, Al2(CO3)3, AlPO4, Al(CH3COO)3, CeCl3, Ce2(SO4)3, Ce2(CO3)3, CePO4, Ce(CH3COO)3, FeCl3, FeSO4, FeCO3, FePO4 , Fe(CH3COO)3, ZrCl4, Zr(SO4)2, Zr(CO3)2, Zr3(PO4)4, Zr(CH3COO)4, NbCl5, Nb2(SO4)5, Nb2(CO3)5, Nb3(PO4)5, Nb(CH3COO)5.

[0045] In some embodiments of the present invention, the electrolyte molecules having a conjugated structure are viologen compounds, imide compounds and anthraquinone compounds, respectively, and their structural formulas are shown in Formulas I, II and III:

[0046]

[0047] Wherein, R1, R2, R3, R4, R5 and R6 are the same or different alkyl groups and substituents, aromatic groups and substituted aromatic groups, and other substituents.

[0048] Furthermore, the alkyl group includes a simple alkyl group, a branched alkyl group, a halogenated alkyl group, a nitrogen-containing alkyl group or a sulfur-containing alkyl group.

[0049] Specifically, simple alkyl groups include -CH3, -C2H5, -C3H7 and C4H9; branched alkyl groups include -CH(CH3)2 and -C(CH3)3; halogenated alkyl groups include -CF3 and -CH2Cl; oxygen-containing alkyl groups include -CH2CH2OH, -CH2CH2OCH3 and -O(CH2CH2O) n H; nitrogen-containing alkyl groups include -NHCH2CH2NH2, -N + (CH3)3; Sulfur-containing alkyl groups include -SO3H and -CH2SH.

[0050] Aromatic and substituted aromatic groups include phenyl, substituted phenyl, and benzyl; phenyl is -Ph. Substituted phenyl groups include -Ph-OCH3, -Ph-NO2, -Ph-NH2, and -Ph-COOR (wherein the R group can be a simple alkyl group, such as methyl, ethyl, propyl, or butyl; a branched alkyl group, such as isopropyl or tert-butyl; an oxygen-containing alkyl group, such as methoxyethyl, ethylene glycol monomethyl ether, or a polyethylene glycol chain; an aromatic group, such as phenyl, or substituted phenyl groups: p-methoxyphenyl or p-nitrophenyl); benzyl is -CH2Ph; other substituents include -CH2Py and -SO3 2- , -COOH, -COO-, -PO3H2, -OH and -PO3 2- wait.

[0051] Exemplarily, X is Cl - 、SO4 2- 、CO3 2- PO4 3- 、CH3COO - .

[0052] Illustratively, in the present invention, the viologen compounds include methyl viologen (MV), ethyl viologen (EV), isopropyl viologen (iPrV), rod-shaped viologen (R-Vi), S-shaped viologen (S-Vi), bishydroxy viologen (BHV), bissulfonic acid viologen (BSV), amino-carboxylic acid viologen (ACV), propyl-3-trimethylamine substituted viologen (BTMAP-Vi or (NPr)2V), 1,4-phenyl conjugated viologen [(NPr)2-1,4-PBPy]Cl4, 1,3-phenyl conjugated viologen [(NPr)2-1,3-PBPy]Cl4 or 1,2-phenyl conjugated viologen [(NPr)2-1,4-PBPy]Cl4.

[0053] Viologen compounds, such as 4,4'-bipyridyl viologen, have two redox-active centers in their bipyridyl salt structure, capable of storing two electrons, and the two-electron reduction process occurs at more negative potentials. Excessively negative potentials result in a high negative charge density on the electrode surface, triggering a proton-coupled electron transfer reaction that causes water to decompose into hydrogen atoms or hydrogen gas. Commonly used negative electrolyte molecules undergo a more negative state during the reduction process, where residual hydroxide ions in the water initiate a dealkylation reaction through nucleophilic attack, breaking the C(alkyl)-N bond of the viologen electrolyte active molecules and causing structural inactivation. This leads to irreversible capacity loss and reduced cycle life in neutral aqueous organic flow batteries. By adding a high concentration of salt, the decomposition of water into hydrogen atoms or hydrogen gas is prevented, thereby preventing the formation of large amounts of hydroxide ions in the water to attack and initiate the dealkylation reaction, thus extending the service life of the entire electrolyte.

[0054] In some embodiments of the present invention, the anthraquinone compounds include: 9,10-anthraquinone-2,7-disulfonic acid (AQDS), 2,6-dihydroxyanthraquinone (2,6-DHAQ) or 1,4-dihydroxyanthraquinone (1,4-DHAQ).

[0055] For anthraquinone compounds, during the negative electrode reaction, the reduction reaction of anthraquinone compounds usually involves the transfer of multiple electrons (such as two-electron reduction reaction). These reactions usually occur during the reduction process of the negative electrode. The multi-electron reduction reaction of quinone compounds usually occurs in a lower potential range and is easy to compete with the hydrogen evolution reaction for electrical energy. When the negative electrode potential of the battery is too low, the hydrogen ions (H + ) will be reduced to hydrogen (H2), which is the process of hydrogen evolution reaction. The hydrogen evolution reaction will significantly reduce the energy efficiency of the battery because the battery's electrical energy is wasted on the generation of hydrogen instead of being used for the reduction of quinone compounds, thereby reducing the reduction reaction of quinone compounds. In addition, the occurrence of hydrogen evolution reaction may lead to the accumulation of bubbles inside the battery, which will affect the stability and service life of the battery. And in the reduction process of quinone compounds, due to the transfer of electrons and changes in molecular structure, some chemical bonds may break, especially the CH bond, CC bond or C=O bond in quinone compounds. This change in molecular structure may cause the quinone compound to be inactivated, affecting the long-term performance and cycle stability of the battery. If the electrode potential is too low, the hydrolysis reaction or the generation of hydroxide ions may further aggravate the breakage of the bond, thereby accelerating the degradation of the electrolyte. The introduction of a high concentration of salt solution can significantly increase the ionic strength of the electrolyte solution, which reduces the concentration of hydrogen ions in the water molecules, thereby reducing the probability of the occurrence of the hydrogen evolution reaction. At high salt concentrations, the threshold potential of the hydrogen evolution reaction tends to increase, thereby reducing the competition for the hydrogen evolution reaction.

[0056] In some embodiments of the present invention, the imide compounds mainly include: perylenetetracarboxylic acid imide (PTCDI), naphthalenetetracarboxylic acid imide (NTCDI), biphenyltetracarboxylic acid imide (BPCDI), anthracenetetracarboxylic acid imide (ANTCDI), pyrenetetracarboxylic acid imide (PyTCDI), naphthalene diimide (NDI), benzothiophene diimide (BTDI), tetrathiafulvalen diimide (TTFDI), and polyether chain modified imide (such as PEG-NDI). For the imide compounds, the imide compounds realize a reversible two-electron redox reaction through a π-conjugated skeleton and an imide group (-CONHCO-), and the reaction process is related to protons (H + ) transfer is highly cooperative, and the two-electron redox process is as follows: the carbonyl group (C=O) of the imide accepts electrons and protons, and is converted into an enol structure (CO- and CH), forming a stable reduced state. The reduced enol structure releases electrons and protons, and returns to the oxidized imide. Imide compounds are usually hydrophobic, but through functional modification, they can achieve high solubility and long-term stability in neutral aqueous solution. Imide compounds use an extended π conjugated skeleton (such as perylene, anthracene, and naphthalene) to enable rapid migration of electrons within the molecule, thereby reducing the activation energy of the redox reaction. Cations in the electrolyte (such as Na + , K + ) combines with the π electron cloud of imide to form an ion-π complex, which promotes charge separation and transport; and the planar structure of imide can be adsorbed on the surface of carbon-based electrodes (such as graphite felt) to form a dense active layer, thereby reducing interfacial impedance.

[0057] As a preferred solution, the concentration of the organic active substance is 0.01 to 0.1 mol / L.

[0058] In some embodiments of the present invention, performance optimization can be achieved by adding a multivalent inorganic cation or any combination of ions with different valences to the electrolyte. This combination can be customized according to the specific battery system and reaction mechanism.

[0059] In some embodiments of the present invention, when two or more types of inorganic cations are added, different ions will have different effects: for example, different ion effects: different types of ions can coordinately regulate the properties of the electrolyte through differences in charge, size, and solvation ability, thereby optimizing the conductivity and ion transport: high-valent ions (such as Mg 2+ 、Al 3+ ) through strong charge shielding effect, weakening the Coulomb repulsion between active substances (such as quinones, imides), inhibiting aggregation; low-valent ions (such as Na + , K + ) Fast migration rate (such as K + Mobility ratio Mg 2+3-5 times higher), improving the overall conductivity, and also achieving solubility and stability control. The difference in the binding ability of different ions and active substances can adjust the dissolution balance.

[0060] For example, in a specific embodiment, the electrolyte molecule is a sulfonic acid active substance (AQDS), and the inorganic cation is Al 3+ and Na + The sulfonic acid groups of the active substances preferentially bind to the high-valent Al 3+ Combined to form a soluble complex, improving the stability of AQDS, while Na + Acts as an "inert ion" to maintain the ionic strength of the solution and prevent precipitation.

[0061] For example, in a specific embodiment, the electrolyte molecule is a hydroxyl active substance 2,6-dihydroxyanthraquinone (2,6-DHAQ), which is 2+ The solubility is improved when there is excess Ca 2+ May cause gelation, need to add K + balance.

[0062] In some embodiments of the present invention, different ions can also achieve redox potential regulation, high-valent ions (such as Al 3+ ) changes the electron cloud distribution of the active substance through strong polarization, causing its redox potential to shift; Antioxidant protection: mixed ions inhibit the oxidative decomposition of active substances through physical adsorption or chemical coordination: Free radical scavenging: high-valent ions (Fe 3+ 、Ce 3+ ) can capture free radicals generated during the oxidation process: such reactions reduce the irreversible oxidation of active substances (such as quinones) and improve cyclic stability.

[0063] Coordination stabilization: multivalent ions (Mg 2+ 、Zn 2+ ) coordinates with the functional groups (-COOH, -NH2) of organic molecules to form stable complexes: such as Mg 2+ After coordination with 2,6-dihydroxyanthraquinone (2,6-DHAQ), its oxidized half-life was extended by 5 times and its resistance to air oxidation was significantly enhanced.

[0064] As a preferred solution, in some embodiments of the present invention, monovalent inorganic cations and divalent inorganic cations are added to the negative electrode solution together. Taking potassium ions and calcium ions as an example, they are added to the negative electrode solution together: potassium ions migrate quickly, which can improve the conductivity of the electrolyte and also serve as a "supporting electrolyte" to maintain the ionic strength; while calcium ions reduce the Coulomb repulsion between ions through the charge shielding effect, reduce the aggregation of active substances, and can coordinate with certain organic molecular functional groups (such as carboxylic acid groups) to inhibit molecular decomposition.

[0065] Calcium ions can also inhibit hydrogen and oxygen evolution side reactions by adsorbing on the electrode surface. When mixed with conjugated structures, calcium ions coordinate with negatively charged groups (such as sulfonic acid and carboxylic acid groups) on the conjugated molecules, improving solubility and potentially polarizing the electron cloud of the conjugated molecules, regulating their redox potential. Potassium ions, through the ion-pair effect, can reduce precipitation caused by intermolecular π-π stacking. Ionic mixing can induce conjugated molecules to form ordered nanostructures (such as micelles or lamellar phases), thereby improving charge transfer efficiency.

[0066] On this basis, for example, calcium ions and potassium ions can be used in conjunction with polysulfonic acid conjugated molecules to achieve better results: polysulfonic acid conjugated molecules: such as 9,10-anthraquinone-2,7-disulfonic acid (AQDS); during the use of the sulfonic acid group (-SO3 - ) strongly coordinates with calcium ions to form a stable water-soluble complex. Potassium ions balance the charge density and prevent gelation caused by excessive calcium ions.

[0067] For example, calcium ions and potassium ions simultaneously coordinate with carboxylic acid / amine conjugated compounds and are used in negative electrode electrolytes: for example, the oxygen and nitrogen functional groups in 2,6-DHAQ form coordination bonds with calcium ions, enhancing molecular rigidity and inhibiting side reactions.

[0068] For example, calcium ions and potassium ions simultaneously react with oxygen-containing heterocyclic conjugated molecules: for example, heteroatoms (such as N and O) in viologen derivatives (such as dihydroxy viologen) will coordinate with calcium ions to stabilize redox intermediates; potassium ions will reduce the viscosity of the electrolyte through a weak solvation effect and improve the rate performance.

[0069] In some embodiments of the present invention, divalent inorganic cations and trivalent inorganic cations are added to the negative electrode solution together. For example, magnesium ions and aluminum ions are added to the negative electrode solution together as an example: Al 3+ The strong polarization ability of Al can enhance the coordination with organic molecules, thereby inhibiting side reactions. 3+ After adsorption on the electrode surface, Mg can also inhibit the hydrogen evolution reaction and broaden the voltage window. 2+ As a "supporting ion" can reduce Al 3+ Risk of gelation.

[0070] Furthermore, when mixed with conjugated structures, the π electron cloud of the conjugated molecules (such as anthraquinone and viologen) can interact with high-valent metal ions (Al 3+ ) form ion-π interactions to stabilize the oxidation state. The multidentate ligand groups (such as carboxylic acid, sulfonic acid, phosphoric acid) and Mg 2+ / Al 3+ Strong coordination to prevent ion hydrolysis or precipitation. 3+ The coordination rigidity of Mg can reduce the change of molecular configuration and lower the reaction overpotential.2+ / Al 3+ Mixed ions may induce the conjugated molecules to form lamellar or micellar structures, which can provide fast ion diffusion channels.

[0071] For example, in a specific embodiment, the inorganic cation in the negative electrode electrolyte is Mg 2+ and Al 3+ The electrolyte molecule is tetracarboxylic anthraquinone (TCAQ), which contains four carboxylic acid groups and can react with Mg 2+ and Al 3+ Form a stable coordination network.

[0072] For example, in a specific embodiment, the inorganic cation in the negative electrode electrolyte is Mg 2+ and Al 3+ The electrolyte molecule is dihydroxyviolet (BHV), which has both a conductive polymer skeleton and a carboxylic acid coordination site. The carboxylic acid group (-COOH) is very sensitive to Mg 2+ and Al 3+ high affinity, enhancing solubility and circulation stability.

[0073] For example, in a specific embodiment, the inorganic cation in the negative electrode electrolyte is Mg 2+ and Al 3+ The electrolyte molecule is 9,10-anthraquinone-2,7-disulfonic acid (AQDS): the sulfonic acid group (-SO3 - ) and Al 3+ Will produce strong coordination.

[0074] For example, in a specific embodiment, the inorganic cation in the negative electrode electrolyte is Mg 2+ and Al 3+ The electrolyte molecule is disulfonic acid viologen (BSV): it can expand the conjugated structure to increase the electron transfer rate, and the sulfonic acid group provides high water solubility and anti-precipitation ability, which is suitable for high concentration Al 3+ system. And Mg 2+ Acts as a counter ion to balance the charge and prevent excessive aggregation of molecules.

[0075] For example, in a specific embodiment, the inorganic cation in the negative electrode electrolyte is Mg 2+ and Al 3+ The electrolyte molecule is amino-carboxylic acid viologen (ACV): the amino group can react with Al 3+ Coordinated with Mg 2+ Combined with each other, a bimetallic coordinated coordination network is formed. In addition, the protonation of the amino group can regulate the charge state of the molecule and optimize the redox potential.

[0076] As a preferred solution, in some embodiments of the present invention, the inorganic cation valence state added is all above trivalence, such as trivalence, tetravalence or pentavalence, and as the inorganic cation valence state and ionic radius increase, the steric hindrance produced can change the planar conjugated structure of the organic molecule, optimize the stacking of the conjugated structure, and combine with the polar groups in the organic molecule by stronger electrostatic interaction, while enhancing the stability of the hydrogen bond network, stabilizing the conjugated structure. Exemplary, the inorganic cation added in the electrolyte can be a mixed substance of aluminum ion and cerium ion, a mixed substance of aluminum ion and zirconium ion, and can also be a mixed substance of niobium ion and iron ion. When monovalent and pentavalent cations are added to mix, monovalent cations (such as potassium ions) are usually used as supporting electrolytes to improve the conductivity of the system, while pentavalent cations (such as niobium ions) are usually highly oxidizing and have a high charge density. And it may form a complex with the oxygen-containing groups (such as -COOH, etc.) of the organic molecule to enhance the stability of the system. When divalent and trivalent cations are added to the mixture, divalent cations (such as calcium ions) can form stable coordination bonds with the carboxylic acid or sulfonic acid groups of organic molecules, thereby improving their solubility. They can also act as "buffer ions" to alleviate the strong coordination effect of trivalent cations, while trivalent cations (such as aluminum ions) can form a rigid coordination network with organic molecules to inhibit molecular degradation.

[0077] In some specific embodiments of the present invention, the organic active substance viologen electrolyte molecules show the best matching effect with divalent magnesium ions.

[0078] As a preferred solution, the monovalent inorganic cation is potassium ion; the divalent inorganic cation is calcium ion and magnesium ion; and the trivalent inorganic cation is aluminum ion.

[0079] More preferably, the inorganic cation used is a divalent magnesium ion. Magnesium ions can form specific complexes or ion pairs with negative electrode electrolyte molecules having a conjugated structure, thereby improving the stability of the electrolyte.

[0080] More preferably, the ratio of the added divalent magnesium ions to the negative electrode electrolyte molecules is 1:2.

[0081] As a preferred solution, the concentration of the added inorganic cations is 0.025 to 0.25 mol / L. The higher the concentration of the inorganic cations, the stronger the interaction with the electrolyte molecules.

[0082] In some embodiments of the present invention, the salt solution is an aqueous solution of potassium chloride or sodium chloride, and the concentration of the supporting electrolyte solution is 1 mol / L; it should be understood that the concentration of the salt solution can be further adjusted as needed, such as 0.5 mol / L, 2 mol / L, and 3 mol / L.

[0083] The present invention discloses an aqueous organic liquid flow battery. The aqueous organic liquid flow battery consists of a positive electrode electrolyte, a positive electrode flow field plate, a positive electrode, an ion separator, a negative electrode, a negative electrode flow field plate and a negative electrode electrolyte; wherein the positive electrode electrolyte adopts a cyclic nitroxide free radical compound or a ferrocene compound, and the negative electrode adopts the above-mentioned negative electrode electrolyte.

[0084] As a preferred solution, 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.

[0085] The following is a collection of specific examples for further analysis.

[0086] Comparative Example 1

[0087] Take 0.05mol / L of viologen compound MV and place it in 1mol / L NaCl solution to obtain the negative electrode electrolyte required for the experiment. The structural formula of the viologen compound used in the negative electrode electrolyte is shown below (a); take 0.05mol / L TMA-TEMPO and place it in 1mol / L NaCl solution to obtain the positive electrode electrolyte required for the experiment. The structural formula of the TMA-TEMPO compound used in the positive electrode electrolyte is shown below (b). Then assemble the liquid flow battery device, inject the prepared electrolyte into the electrolyte tank, assemble the liquid flow battery, install a peristaltic pump, connect to the battery testing system, and perform constant current charge and discharge tests.

[0088]

[0089] (a)MV

[0090]

[0091] (b)TMA-TEMPO

[0092] Example 1

[0093] Take 0.05mol / L of violet compound MV and place it in 1mol / L NaCl solution to obtain the negative electrode electrolyte required for the experiment; take 0.05mol / L TMA-TEMPO and place it in 1mol / L NaCl solution to obtain the positive electrode electrolyte required for the experiment. After adding 0.025 and 0.25mol / L CaCl2 solutions to the negative electrode electrolyte, respectively, the prepared electrolyte was injected into the electrolyte tank, the flow battery was assembled, equipped with a peristaltic pump, connected to the battery testing system, and a constant current charge and discharge test was performed. In the aqueous neutral liquid flow battery to which 0.025 and 0.25mol / LCaCl2 solutions were added, respectively, under the same number of cycles, the capacity percentage of the aqueous neutral liquid flow battery to which 0.025mol / L CaCl2 solution was added was shown to be optimal. Comparing it with the capacity percentage of the aqueous neutral liquid flow battery to which no ions were added, as shown in FIG. Figure 1 As shown in the results, it was found that under the same number of cycles, the capacity percentage of the battery with 0.025mol / L CaCl2 solution was greatly improved compared with that without it. And the changes of capacity and voltage with cycles were tested and compared. Figure 3 and Figure 4 As shown in Figure 3, it was found that the capacity decay after cycling was smaller when calcium ions were added than when monovalent potassium ions were added.

[0094] Example 2

[0095] Take 0.05mol / L of violet compound MV and place it in 1mol / L NaCl solution to obtain the negative electrode electrolyte required for the experiment; take 0.05mol / L TMA-TEMPO and place it in 1mol / L NaCl solution to obtain the positive electrode electrolyte required for the experiment. After adding 0.025 and 0.25mol / LMgCl2 to the negative electrode electrolyte respectively, the prepared electrolyte was injected into the electrolyte tank, the flow battery was assembled, equipped with a peristaltic pump, connected to the battery testing system, and constant current charge and discharge tests were carried out. In the aqueous neutral liquid flow battery to which 0.025 and 0.25mol / L MgCl2 solutions were added respectively, under the same number of cycles, the capacity percentage of the battery with 0.025mol / L MgCl2 solution added was shown to be optimal. Compare it with the capacity percentage of the aqueous neutral liquid flow battery to which no ions were added, as shown in FIG. Figure 1 As shown in the figure, the results show that the capacity percentage of the aqueous neutral flow battery with 0.025 mol / L MgCl2 solution is the best under the same number of cycles compared with the aqueous neutral flow battery without ions and with MgCl2 ions. The changes in capacity and voltage with cycles are shown in the figure. Figure 3 and Figure 5 As shown in Figure 3, it was found that the capacity decay after cycling was smaller when magnesium ions were added than when monovalent cations were added.

[0096] Example 3

[0097] Take 0.05mol / L of violet essence compound MV and place it in 1mol / L NaCl solution to obtain the negative electrode electrolyte required for the experiment; take 0.05mol / L TMA-TEMPO and place it in 1mol / L NaCl solution to obtain the positive electrode electrolyte required for the experiment. Prepare three groups of positive and negative electrode electrolytes mentioned above, select one group without additives as the blank control group, add 0.025 and 0.25mol / L MgCl2 to the remaining two groups of negative electrode electrolytes respectively, while the positive electrode has no additives, and the volume of the negative electrode electrolyte is controlled to be 1.5 times that of the positive electrode. Inject the prepared electrolyte into the electrolyte tank, assemble the flow battery, install a peristaltic pump, connect to the battery testing system, and perform constant current charge and discharge tests. Figure 2As shown, the results showed that under the same number of cycles, the normalized capacity of the aqueous neutral flow battery with 0.025 mol / LMgCl2 added to the negative electrode electrolyte was the best.

[0098] Comparative Example 2

[0099] Weigh 12.5 grams of viologen compound (NPr) 2V into a measuring cup, add deionized water, stir to dissolve, and dilute to 10 milliliters with NaCl solution to prepare the negative electrolyte. The structural formula of viologen compound (NPr) 2V is shown below. Weigh 1.07 grams of TMA-TEMPO compound into a measuring cup, add deionized water, stir to dissolve, and dilute to 10 milliliters with NaCl solution to prepare the positive electrolyte. The flow battery device was then assembled, and the prepared electrolyte was injected into the electrolyte tank. The flow battery was assembled, equipped with a peristaltic pump, and connected to a battery testing system for constant current charge and discharge testing.

[0100]

[0101] Example 4

[0102] Weigh 12.5 g of viologen compound (NPr) 2V and 0.475 g of MgCl2 and add them to a measuring cup in sequence, add deionized water, stir to dissolve and dilute to 10 ml with NaCl solution to prepare a negative electrolyte; weigh 1.07 g of TMA-TEMPO compound and add it to a measuring cup, add deionized water, stir to dissolve and dilute to 10 ml with NaCl solution to prepare a positive electrolyte; then assemble the flow battery device, inject the prepared electrolyte into the electrolyte tank, assemble the flow battery, install a peristaltic pump, connect to the battery testing system, and perform constant current charge and discharge tests. Comparing Comparative Example 2 and Example 4, as shown in FIG. Figure 6 As shown in the figure, the results show that under the same number of cycles, the capacity percentage of the aqueous neutral flow battery with the addition of MgCl2 is higher than that of the aqueous neutral flow battery without the addition of ions. The capacity and voltage changes with the cycle are tested, and the addition of monovalent ions and Mg ions are compared. Figure 3 and Figure 7 As shown, it is found that the capacity decay after cycling is small.

[0103] Example 5

[0104] The negative electrolyte for the experiment was prepared by dissolving 0.1 mol / L of the viologen compound MV in a 1 mol / L NaCl solution. The positive electrolyte for the experiment was prepared by dissolving 0.1 mol / L of TMA-TEMPO in a 1 mol / L NaCl solution. After adding 0.025 mol / L of MgCl₂ to the negative electrolyte, the prepared electrolyte was poured into the electrolyte tank to assemble the flow battery.

[0105] Example 6

[0106] The negative electrolyte for the experiment was prepared by dissolving 0.01 mol / L of the viologen compound MV in a 1 mol / L NaCl solution. The positive electrolyte for the experiment was prepared by dissolving 0.01 mol / L of TMA-TEMPO in a 1 mol / L NaCl solution. After adding 0.025 mol / LMgCl₂ to the negative electrolyte, the prepared electrolyte was poured into the electrolyte tank to assemble the flow battery.

[0107] Example 7

[0108] The negative electrolyte for the experiment was prepared by dissolving 0.05 mol / L of the viologen compound MV in a 1 mol / L NaCl solution. The positive electrolyte for the experiment was prepared by dissolving 0.05 mol / L of TMA-TEMPO in a 1 mol / L NaCl solution. After adding 3 mol / LMgCl₂ to the negative electrolyte, the prepared electrolyte was poured into the electrolyte tank to assemble the flow battery.

[0109] Example 8

[0110] The negative electrolyte for the experiment was prepared by dissolving 0.05 mol / L of the viologen compound MV in a 1 mol / L NaCl solution. The positive electrolyte for the experiment was prepared by dissolving 0.05 mol / L of TMA-TEMPO in a 1 mol / L NaCl solution. After adding 1 mol / LMgCl₂ to the negative electrolyte, the prepared electrolyte was poured into the electrolyte tank to assemble the flow battery.

[0111] Example 9

[0112] The negative electrolyte for the experiment was prepared by dissolving 0.05 mol / L of the viologen compound MV in a 1 mol / L NaCl solution. The positive electrolyte for the experiment was prepared by dissolving 0.05 mol / L of TMA-TEMPO in a 1 mol / L NaCl solution. 2 mol / LMgCl₂ was added to the negative electrolyte and then poured into the electrolyte tank to assemble the flow battery.

[0113] Example 10

[0114] The negative electrolyte for the experiment was prepared by dissolving 0.05 mol / L AQDS in a 1 mol / L NaCl solution. The positive electrolyte for the experiment was prepared by dissolving 0.05 mol / L TMA-TEMPO in a 1 mol / L NaCl solution. AlCl₃ and NaCl were added to the negative electrolyte to a total concentration of 2 mol / L. This electrolyte was then poured into the electrolyte tank to assemble the flow battery.

[0115] Example 11

[0116] The negative electrolyte for the experiment was prepared by dissolving 0.05 mol / L AQDS in a 1 mol / L NaCl solution. The positive electrolyte for the experiment was prepared by dissolving 0.05 mol / L TMA-TEMPO in a 1 mol / L NaCl solution. After adding 0.05 mol / L CaCl2 to the negative electrolyte, the prepared electrolyte was poured into the electrolyte tank to assemble the flow battery.

[0117] Example 12

[0118] The negative electrolyte for the experiment was prepared by dissolving 0.05 mol / L DHAQ in a 1 mol / L NaCl solution. The positive electrolyte for the experiment was prepared by dissolving 0.05 mol / L TMA-TEMPO in a 1 mol / L NaCl solution. After adding 2 mol / L MgCl2 to the negative electrolyte, the prepared electrolyte was poured into the electrolyte tank to assemble the flow battery.

[0119] Example 13

[0120] The negative electrolyte for the experiment was prepared by dissolving 0.05 mol / L AQDS in a 1 mol / L NaCl solution. The positive electrolyte was prepared by dissolving 0.05 mol / L TMA-TEMPO in a 1 mol / L NaCl solution. KCl and CaCl₂ were added to the negative electrolyte to a total concentration of 1 mol / L. This solution was then poured into the electrolyte tank to assemble the flow battery.

[0121] Example 14

[0122] The negative electrolyte required for the experiment was prepared by dissolving 0.05 mol / L of BHV in a 1 mol / L NaCl solution. The positive electrolyte required for the experiment was prepared by dissolving 0.05 mol / L of TMA-TEMPO in a 1 mol / L NaCl solution. KCl and CaCl₂ were added to the negative electrolyte to a total concentration of 1 mol / L. The prepared electrolyte was then poured into the electrolyte tank to assemble the flow battery.

[0123] Example 15

[0124] The negative electrolyte for the experiment was prepared by dissolving 0.05 mol / L TCAQ in a 1 mol / L NaCl solution. The positive electrolyte for the experiment was prepared by dissolving 0.05 mol / L TMA-TEMPO in a 1 mol / L NaCl solution. KCl and CaCl₂ were added to the negative electrolyte to a total concentration of 1 mol / L. This solution was then poured into the electrolyte tank to assemble the flow battery.

[0125] Example 16

[0126] The negative electrolyte for the experiment was prepared by dissolving 0.05 mol / L of the viologen compound BHV in a 1 mol / L NaCl solution. The positive electrolyte was prepared by dissolving 0.05 mol / L of TMA-TEMPO in a 1 mol / L NaCl solution. Al2(SO4)3 and MgSO4 were added to the negative electrolyte to a total concentration of 1 mol / L. The resulting electrolyte was then poured into the electrolyte tank to assemble the flow battery.

[0127] 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 principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A negative electrode electrolyte in an aqueous organic liquid flow battery, characterized in that including organic active substances, inorganic cations and supporting electrolyte solutions; The organic active substance is a redox active molecule having a conjugated structure; The inorganic cation is selected from any one or more of monovalent cations, divalent cations, trivalent cations, tetravalent cations and pentavalent cations; The supporting electrolyte solution is a water-soluble salt solution.

2. The negative electrode electrolyte in an aqueous organic liquid flow battery according to claim 1, characterized in that: The monovalent cation is selected from potassium ion or its hydrate, sodium ion or its hydrate, lithium ion or its hydrate, and ammonium ion or its hydrate.

3. The negative electrode electrolyte in an aqueous organic liquid flow battery according to claim 1, characterized in that: The divalent cation is selected from calcium ion or its hydrate, magnesium ion or its hydrate, and barium ion or its hydrate.

4. The negative electrode electrolyte in an aqueous organic liquid flow battery according to claim 1, characterized in that: The trivalent cation is selected from aluminum ion or its hydrate, cerium ion or its hydrate, and iron ion or its hydrate.

5. The negative electrode electrolyte in an aqueous organic liquid flow battery according to claim 1, characterized in that: The tetravalent cation is a zirconium ion or a hydrate thereof; the pentavalent cation is a niobium ion or a hydrate thereof.

6. The negative electrode electrolyte in an aqueous organic liquid flow battery according to claim 1, characterized in that: The redox active molecule with a conjugated structure is any one of viologen, imide and anthraquinone compounds.

7. The negative electrode electrolyte in an aqueous organic liquid flow battery according to claim 1, characterized in that: The concentration of the inorganic cation is 0.025 to 3 mol / L.

8. The negative electrode electrolyte in an aqueous organic liquid flow battery according to claim 1, characterized in that: The concentration of the organic active electrolyte is 0.01-3.0 mol / L.

9. The negative electrode electrolyte in an aqueous organic liquid flow battery according to claim 1, characterized in that: The inorganic cations include at least two types of inorganic cations.

10. The negative electrode electrolyte in an aqueous organic liquid flow battery according to claim 9, characterized in that: The two types of inorganic cations have the same valence.

11. The negative electrode electrolyte in an aqueous organic liquid flow battery according to claim 9, characterized in that: The two types of inorganic cations have different valence states; Preferably, the valence states of the two types of inorganic cations are monovalent and trivalent; Preferably, the valence states of the two types of inorganic cations are divalent and trivalent, respectively.

12. The negative electrode electrolyte in an aqueous organic liquid flow battery according to claim 1, characterized in that: The valence of the inorganic cation is greater than or equal to trivalence.

13. An aqueous organic liquid flow battery, characterized in that: It includes a positive electrode electrolyte, a positive electrode flow field plate, a positive electrode, an ion diaphragm, a negative electrode, a negative electrode flow field plate and a negative electrode electrolyte; the positive electrode electrolyte is an aqueous solution of a cyclic nitroxide free radical compound or a ferrocene compound, and the negative electrode electrolyte is the negative electrode electrolyte according to claim 1.

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