Hybrid energy storage materials based on phenazine resonating hybrids for aqueous flow battery

Abstract

The application provides a phenazine resonance hybrid-based aqueous flow battery energy storage material, in particular, the application provides a phenazine resonance hybrid compound capable of being used as an aqueous flow battery energy storage material. The compound is simple to prepare, and the prepared battery energy storage material has good cycle stability and energy efficiency, and is suitable for being used as an aqueous flow battery energy storage material.

Description

Technical Field

[0001] This invention belongs to the field of synthesis of multi-substituted phenazine resonant hybrid energy storage materials and aqueous flow battery energy storage technology. Specifically, it relates to several methods for synthesizing multi-substituted phenazine derivative resonant hybrids with redox activity, and their application in aqueous flow battery energy storage systems. Background Technology

[0002] Aqueous flow batteries (ARFBs), as one of the most promising large-scale energy storage technologies, have attracted increasing attention from academia and industry. Flow batteries utilize the transition between oxidized and reduced states of two active materials in fluid form to achieve energy conversion between electrical and chemical energy. Flow battery energy storage technology can be used to improve the utilization rate of clean energy and achieve peak shaving and valley filling of the power grid.

[0003] Organic molecules hold immense potential for application in aqueous organic redox flow batteries (AORFBs), potentially leading to a significant reduction in the levelized cost of energy storage. Compared to inorganic molecules, organic molecules possess inherent advantages due to their structural diversity and tunability, as well as their availability from elements abundant on Earth. These properties contribute to optimizing battery performance and promoting the sustainability of energy storage technologies. While theoretically any organic compound capable of undergoing reversible redox reactions could be a candidate for active material in aqueous organic redox flow batteries (AORFBs), only a limited number of organic compounds have proven to be promising energy storage materials. However, most of them exhibit high capacity decay rates. A major reason for this is that water can undergo nucleophilic addition or substitution reactions, such as Michael addition and hydrolysis, which significantly impact the long-term cycling performance of the battery. Therefore, developing stable organic reductive active materials capable of operating effectively in complex electrochemical environments is crucial.

[0004] To mitigate water-induced degradation within a certain pH range, larger conjugated systems have been shown to offer greater stability; for example, extending benzoquinone to anthraquinone and pyrazine to phenazine. However, in the reduced state, the electron density of the extended, highly conjugated aromatic systems is higher than that in their oxidized state. To achieve a more stable, lower-energy configuration, molecules undergo intermolecular or intramolecular structural rearrangement to redistribute electrons, ultimately existing in a most stable, low-energy state. This is the driving force behind the spontaneous occurrence of side reactions. Therefore, developing strongly conjugated organic redox systems, through directed induction, to achieve appropriate electron densities during electron gain and loss to suppress attacks from water or other nucleophiles, while avoiding side reactions such as isomerization caused by excessively high electron densities, is crucial for advancing stable AORFBs.

[0005] Therefore, there is an urgent need in this field to provide a novel aqueous flow battery energy storage material. Summary of the Invention

[0006] This invention designs and synthesizes a series of stable polysubstituted phenazine compounds based on phenazine structures. Resonance hybrids are synthesized by adjusting substituents, allowing for the control of potential and solubility. The novel framework designed using the resonance strategy significantly improves the stability of the compounds in both reduced and oxidized states. The strategy of combining chemical and electrochemical synthesis reduces the difficulty of synthesis and simplifies the steps. Using non-corrosive and non-flammable pH-neutral aqueous solutions and inexpensive inorganic salts as supporting electrolytes offers advantages such as high safety, low corrosivity, low cost, and environmental friendliness. Battery cycling results demonstrate that these compounds exhibit high concentration and long-cycle stability in aqueous flow batteries.

[0007] A first aspect of the invention provides a compound of the following formula, or a salt thereof which has optionally lost a H atom, or a salt formed with a charge-balancing ion:

[0008]

[0009] In the formula, Z and E can be the same or different, and each is independently selected from the following group: N, P, PO, As, Sb, O, S, SO, SO2, Se or Te;

[0010] m and n are each independently 0 or 1;

[0011] R 1 R 2 R 3 R 4 R 5 R 6 R 7 R 8 R is independently selected from the group consisting of: H, halogen, substituted or unsubstituted C1-C10 alkyl, C3-C8 cycloalkyl, 3-8 membered heterocyclic group, substituted or unsubstituted C6-C10 aryl, hydroxyl, thiol, amino, carboxyl, phosphate, sulfonic acid, or the following water-soluble groups:

[0012] Wherein, Y is a chemical bond, O, NH, NMe, CH2, or S; and R 1 R 2 R 3 R 4 R 5 R 6 R 7 R 8 At least one of them is not H;

[0013] R 9 R 10Each is independently selected from the group consisting of: H, substituted or unsubstituted C1-C10 alkyl groups; or R. 9 R 10 Together with the carbon atoms attached to them, they form groups selected from the following group: C3-C8 cycloalkyl groups, 3-8 membered heterocyclic groups;

[0014] k is selected from the following group: 1, 2, 3, 4, 5, 6, 7, 8;

[0015] R 0 Selected from the following groups: -COOX, -SO3X, -PO3X, -NH2·HQ, -NHCH3·HQ, -N(CH3)2·HQ, -N + (CH3)3M - Q is selected from the following group: Cl - SO4 2- ;

[0016] X is selected from the following group: H + NH4 + Li + Na + K + Mg 2+ Al 3+ Ca 2+ M - Selected from the following group: F - Cl - ,Br - I - OH - OAc - OTf - OTs - SO4 2- SO3 2- PO4 3- HPO4 2- H2PO4 - NO2 - NO3 - CO3 2- HCO3 - ClO4 - ClO3 - ClO2 - ,ClO - CN - wait;

[0017] The charge-balancing ion is a cation or anion, and the cation is selected from the group consisting of H. + NH4 + Li + Na + K + Mg2+ Al 3+ Ca 2+ The anion or M - Selected from the following group: F - Cl - ,Br - I - OH - OAc - OTf - OTs - SO4 2- SO3 2- PO4 3- HPO4 2- H2PO4 - NO 2- NO3 - CO3 2- HCO3 - ClO4 - ClO3 - ClO2 - ,ClO - CN - Furthermore, the compound is electrically neutral.

[0018] The substitution refers to the substitution of one or more hydrogen atoms on the group by a substituent selected from the group consisting of: halogen, C1-C6 alkyl, C6-C10 aryl, hydroxyl, thiol, amino, carboxyl, phosphate, and sulfonic acid groups; the heteroatom in the heterocyclic group is N, O, or S.

[0019] In another preferred example, when R 2 R 3 R 6 R 7 Each is independently selected from CH2 - ,NH - O - ,SiH2 - ,PH - ,S - At that time, the general formula has the following resonance form:

[0020]

[0021] In another preferred embodiment, the R 1 R 2 R 3 R 4 R 5 R 6 R 7 R 8R is independently selected from the following group: H, halogen, C1-C6 alkyl, hydroxyl, thiol, amino, carboxyl, phosphate, sulfonic acid, or

[0022] Where Y represents a chemical bond, O, or S;

[0023] R 9 R 10 Each is independently selected from the following group: H, C1-C4 alkyl;

[0024] k is selected from the following group: 1, 2, 3, 4, 5, 6, 7, 8;

[0025] R 0 Selected from the following groups: -COOX, -SO3X, -PO3X, -NH2·HQ, -NHCH3·HQ, -N(CH3)2·HQ, -N + (CH3)3M - .

[0026] In another preferred embodiment, Z and E may be the same or different, and each is independently selected from the group consisting of N or P.

[0027] In another preferred embodiment, the R 1 R 2 R 3 R 4 R 5 R 6 R 7 R 8 Each group is independently selected from the following groups: H, halogen, C1-C6 alkyl, hydroxyl, thiol, amino, carboxyl, phosphate, sulfonic acid; R is... Where k is 2, 3, 4, or 5; R 0 Selected from the following group: R 0 Select from the following groups: -COOX, -SO3X, -N + (CH3)3M - M - Selected from the following group: F - Cl - ,Br - I - CN - .

[0028] In another preferred embodiment, the R 1 R 2 R 3 R 4 R 5 R 6 R 7 R 8 Each is independently selected from the following group: H, hydroxyl; R is... Where k is 2, 3, 4, or 5; R 0 Selected from the following group: R 0 Select from the following groups: -COOX, -SO3X, -N + (CH3)3M - M - Selected from the following group: F - Cl - ,Br - I - CN - .

[0029] In another preferred embodiment, the compound is selected from the group consisting of:

[0030]

[0031] A second aspect of the present invention provides a method for preparing a compound as described in the first aspect of the present invention, or a salt thereof which optionally loses a H atom, or a salt thereof formed with a charge-balancing ion, characterized in that the method comprises the steps of:

[0032] An electrochemical workstation was constructed using a KCl solution of the free radical cations shown in Formula I as the positive electrode electrolyte and ZnCl2 as the negative electrode electrolyte. Constant current and constant voltage charge-discharge cycles were performed, and the positive electrode electrolyte was separated after cycling to obtain the aforementioned compound, or alternatively, the compound that has lost H+. + or its salts with charge-balancing ions:

[0033]

[0034] In a third aspect, the present invention provides a flow battery energy storage material, wherein the flow battery energy storage material is prepared using a compound as an active ingredient as described in the first aspect of the present invention.

[0035] In a fourth aspect, the present invention provides a flow battery comprising a compound as an energy storage material as described in the first aspect of the present invention.

[0036] In another preferred embodiment, in the flow battery, the compound as described in the first aspect of the invention serves as the negative or positive electrode solution.

[0037] It should be understood that, within the scope of this invention, the above-described technical features of this invention and the technical features specifically described below (such as in the embodiments) can be combined with each other to form new or preferred technical solutions. Due to space limitations, they will not be described in detail here. Attached Figure Description

[0038] Figure 1 This is a single-crystal structure diagram of compound 1;

[0039] Figure 2 The cyclic voltammogram of compound 1 in 1.0 M KCl solution is shown.

[0040] Figure 3 The cyclic voltammogram of compound 2 in 1.0 M KCl solution is shown.

[0041] Figure 4 The cyclic voltammogram of compound 3 in 1.0 M KCl solution is shown.

[0042] Figure 5 The cyclic voltammogram of compound 4 in 1.0 M KCl solution is shown.

[0043] Figure 6 and Figure 7 The results are from charge-discharge cycle tests of 0.1M compound 1 in 1M KCl solution.

[0044] Figure 8 and Figure 9 The results are from charge-discharge cycle tests of 0.7M compound 1 in H2O solution. Detailed Implementation

[0045] Through long-term and in-depth research, the inventors have developed a compound that can be used as an energy storage material in aqueous flow batteries. The compound is simple to prepare, and the resulting battery energy storage material exhibits good cycle stability and energy efficiency. Based on these findings, the inventors have completed this invention.

[0046] the term

[0047] In this invention, the halogen is F, Cl, Br or I.

[0048] In this invention, the term "C1-C10" refers to having 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10 carbon atoms, "C3-C6" refers to having 3, 4, 5 or 6 carbon atoms, and so on.

[0049] In this invention, the term "alkyl" refers to a saturated linear or branched hydrocarbon moiety. For example, the term "C1-C10 alkyl" refers to a straight-chain or branched alkyl group having 1 to 10 carbon atoms, and includes, without limitation, methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl, pentyl, and hexyl; preferably ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, and tert-butyl.

[0050] In this invention, the term "aryl" or "aromatic ring" refers to a hydrocarbon moiety comprising one or more aromatic rings. Examples of aryl groups include, but are not limited to, phenyl (Ph), naphthyl, pyrene, fluorenyl, anthracene, and phenanthryl.

[0051] In this invention, the term "heteroaryl" refers to a moiety comprising one or more aromatic rings having at least one heteroatom (e.g., N, O, or S). Examples of heteroaryl groups include furanyl, pyrroleyl, thiophenyl, oxazolyl, imidazolyl, thiazolyl, pyridyl, pyrimidinyl, quinazolinyl, quinolinyl, isoquinolinyl, and indoleyl, etc.

[0052] Flow battery

[0053] In flow batteries, the positive and negative electrolytes are stored in external tanks and transported to the battery stack via peristaltic pumps. The active materials undergo redox reactions on the electrode surfaces to store and release energy. Compared to traditional chemical batteries like lithium-ion batteries, flow batteries have the advantage of independent energy and power output; energy depends on the concentration and volume of the storage material, while power depends on the electrode area. As the energy storage scale increases, the cost of this technology becomes closer to the cost of the storage materials. Therefore, although lithium-ion batteries have higher energy density, flow batteries are more suitable for large-scale energy storage power stations. Based on the type of solvent used in the electrolyte, flow batteries are classified into aqueous flow batteries and non-aqueous (organic solvent) flow batteries.

[0054] Aqueous flow batteries are classified into aqueous inorganic flow batteries and aqueous organic flow batteries based on whether the energy storage material used is inorganic or organic. Currently, the most researched and widely used energy storage materials are inorganic materials. However, the high cost, limited resources, tendency to form dendrites during use, and slow electrochemical reaction rates of inorganic materials limit the large-scale application of inorganic flow batteries. Using organic materials as energy storage materials offers a wider range of sources than the limited metals stored in the Earth's crust, lower operating costs, and reduces heavy metal pollution. Compared to inorganic materials, organic materials have advantages such as light weight, low cost, ductility, and plasticity. The electrochemical reaction rate of organic materials is faster, typically 1-2 orders of magnitude faster than inorganic metals, requires no catalyst, and does not form dendrites that damage the separator. Furthermore, synthetic chemists can modify and functionalize them at the molecular level, introducing functional groups to optimize the solubility and redox potential of organic materials, thereby adjusting the battery's energy density and open-circuit voltage. Therefore, studying the structural and electrochemical properties of organic energy storage materials and their possible degradation mechanisms to improve the performance, energy density, and lifespan of aqueous organic flow batteries while reducing their cost is of great significance for promoting the application of flow batteries in the field of energy storage, reducing environmental pollution and energy waste, and meeting the demand for electricity from human production activities.

[0055] Flow battery energy storage materials

[0056] This invention provides a compound that can be used as an organic energy storage material in an aqueous flow battery, or a salt thereof that optionally loses a hydrogen atom or forms with a charge-balancing ion. Specifically, the compound has the following structure:

[0057]

[0058] In the formula, Z and E can be the same or different, and each is independently selected from the following group: N, P, PO, As, Sb, O, S, SO, SO2, Se or Te;

[0059] m and n are each independently 0, 1 or 2;

[0060] R 1 R 2 R 3 R 4 R 5 R 6 R 7 R 8 R is independently selected from the group consisting of: H, halogen, substituted or unsubstituted C1-C10 alkyl, C3-C8 cycloalkyl, 3-8 membered heterocyclic group, substituted or unsubstituted C6-C10 aryl, hydroxyl, thiol, amino, carboxyl, phosphate, sulfonic acid, or the following water-soluble groups:

[0061] Where Y represents chemical bonds, O, NH, NMe, CH2; and R 1 R 2 R 3 R 4 R 5 R 6 R 7 R 8 At least one of them is not H;

[0062] R 9 R 10 Each is independently selected from the group consisting of: H, substituted or unsubstituted C1-C10 alkyl groups; or R. 9 R 10 Together with the carbon atoms attached to them, they form groups selected from the following group: C3-C8 cycloalkyl groups, 3-8 membered heterocyclic groups;

[0063] k is selected from the following group: 1, 2, 3, 4, 5, 6, 7, 8;

[0064] R 0 Selected from the following groups: -COOX, -SO3X, -PO3X, -NH2·HQ, -NHCH3·HQ, -N(CH3)2·HQ, -N + (CH3)3M -Q is selected from the following group: Cl - SO4 2- ;

[0065] X is selected from the following group: H + NH4 + Li + Na + K + Mg 2+ Al 3+ Ca 2+ M - Selected from the following group: F - Cl - ,Br - I - OH - OAc - OTf - OTs - SO4 2- SO3 2- PO4 3- HPO4 2- H2PO4 - NO2 - NO3 - CO3 2- HCO3 - ClO4 - ClO3 - ClO2 - ,ClO - CN - wait;

[0066] The charge-balancing ion is a cation or anion, and the cation is selected from the group consisting of H. + NH4 + Li + Na + K + Mg 2+ Al 3+ Ca 2+ The anion or M - Selected from the following group: F - Cl - ,Br - I - OH - OAc - OTf - OTs - SO4 2- SO3 2- PO4 3- HPO4 2-H2PO4 - NO 2- NO3 - CO3 2- HCO3 - ClO4 - ClO3 - ClO2 - ,ClO - CN - Furthermore, the compound is electrically neutral.

[0067] The substitution refers to the substitution of one or more hydrogen atoms on the group by a substituent selected from the group consisting of: halogen, C1-C6 alkyl, C6-C10 aryl, hydroxyl, thiol, amino, carboxyl, phosphate, and sulfonic acid groups; the heteroatom in the heterocyclic group is N, O, or S.

[0068] In another preferred example, when R 2 R 3 R 6 R 7 Each is independently selected from CH2 - ,NH - O - ,SiH2 - ,PH - ,S - At that time, the general formula has the following resonance form:

[0069]

[0070] It should be understood that, since the above compounds are charge-balanced, they can lose several H atoms. + The presence of ions, or compounds that form electrically neutral compounds with several conventional cations or anions, does not affect the achievement of the objectives of this invention.

[0071] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Experimental methods in the following embodiments, unless otherwise specified, are generally performed under conventional conditions or as recommended by the manufacturer. Percentages and parts are by weight unless otherwise stated.

[0072] Examples (Synthesis and Characterization Data of Compounds)

[0073] Specific examples are as follows:

[0074]

[0075] Example 1: Synthesis of Compounds 1 and 2

[0076]

[0077] Compound 5 was dissolved in 30 mL of 1 M KCl solution to prepare a 0.2 M positive electrolyte, and ZnCl2 was dissolved in 100 mL of 1 M KCl solution to prepare a 0.2 M negative electrolyte. A Nafion 212 cation exchange membrane and AvCarb Felt G100 carbon felt were used as electrode materials. Cyclic testing was performed using a flow battery. Constant current and constant voltage charge-discharge was performed using an electrochemical workstation with a cutoff voltage of 2.2 V–0.9 V. After 16 h of cycling, the positive electrolyte was purified by reverse-phase column chromatography, yielding 2.4 g of target product 1 (red solid) in 76% yield and 198 mg of target product 2 in 7% yield.

[0078] Compound 1 1 H NMR (600MHz, D2O) δ7.70(dd,J=6.5,3.5Hz,1H),7.48(dd,J=6.6,3.3Hz,1H),6.21(s,1H),4.30(s,2H),3.02(t,J=6.8Hz,2H),2.09(m,J=8.0Hz,2H). 13 CNMR(151MHz,D2O)δ178.83,141.80,127.10,126.46,116.35,99.28,47.41,46.73,20.80.HR-MS(ESI)m / z calcd for C 18 H 20 N2O8S2 + [M+H+]457.0739, found 457.0734.

[0079] Compound 2 1 H NMR(500MHz,D2O)δ7.72–7.61(m,2H),7.37(d,J=7.2Hz,2H),6.20(s,1H),4.73(t,2H),4.44(t, 2H), 3.02 (t, J = 7.0Hz, 2H), 2.47 (t, J = 7.3Hz, 2H), 2.22 (m, J = 8.4Hz, 2H), 1.97 (m, J = 7.2Hz, 2H).

[0080] Example 2: Synthesis of compounds 3 and 4

[0081]

[0082] Compound 6 was dissolved in 30 mL of 1 M KCl solution to prepare a 0.2 M positive electrolyte, and ZnCl2 was dissolved in 100 mL of 1 M KCl solution to prepare a 0.2 M negative electrolyte. Anion exchange membranes from Huamo Biotechnology and AvCarb Felt G100 carbon felt were used as electrode materials. Constant current and constant voltage charge-discharge was performed using an electrochemical workstation with a cutoff voltage of 2.4 V–1.0 V for 16 h. After this cycle, the positive electrolyte was purified by reverse-phase column chromatography, yielding 1.0 g of target product 3 (red solid) in 30% yield and 1.0 g of target product 4 in 30% yield.

[0083] Compound 3 1 H NMR(500MHz,D2O)δ7.91(dd,J=6.5,3.5Hz,1H),7.68(dd,J=6.6,3.3Hz,1H),6. 46(s,1H),4.60(s,2H),3.75–3.70(s,2H),3.21(s,9H),2.50(m,J=8.7Hz,2H).

[0084] Compound 4 1 H NMR(500MHz,D2O)δ7.90–7.84(m,1H),7.82(d,J=9.1Hz,1H),7.66–7.56(m,2H),6.36(s,1H),4.92–4.83(m,2H),4.59(d ,J=8.4Hz,2H),3.71(d,J=9.1Hz,2H),3.39–3.27(m,2H),3.22(s,9H),3.05(s,9H),2.52(s,2H),2.26(t,J=8.5Hz,2H).

[0085] Test Example 1: Cyclic Voltammetry Test (Compound 1)

[0086] Cyclic voltammetry was performed using a three-electrode system. The working electrode was a 3mm glassy carbon electrode, the reference electrode was an aqueous Ag / AgCl electrode, and the counter electrode was a platinum mesh electrode. The voltage scan range during testing was -0.6V to -0.1V, and the scan rate was 20mV / s.

[0087] The cyclic voltammogram of compound 1 in 1M KCl solution is shown below. Figure 2 As shown. The results show that this compound exhibits good redox properties under neutral conditions, E 1 / 2 =-0.36V (vs SHE), ΔE=130mV.

[0088] Test Example 2: Cyclic Voltammetry Test (Compound 2)

[0089] Cyclic voltammetry was performed using a three-electrode system. The working electrode was a 3mm glassy carbon electrode, the reference electrode was an aqueous Ag / AgCl electrode, and the counter electrode was a platinum mesh electrode. The voltage scan range during testing was -0.8V to 0.2V, and the scan rate was 20mV / s.

[0090] The cyclic voltammogram of compound 2 in 1M KCl solution is shown below. Figure 3 As shown. The results show that this compound exhibits good redox properties under neutral conditions, E 1 / 2 =-0.18V (vs SHE), ΔE=70mV.

[0091] Test Example 3: Cyclic Voltammetry Test (Compound 3)

[0092] Cyclic voltammetry was performed using a three-electrode system. The working electrode was a 3mm glassy carbon electrode, the reference electrode was an aqueous Ag / AgCl electrode, and the counter electrode was a platinum mesh electrode. The voltage scan range was -0.7V to 1.2V, and the scan rate was 20mV / s.

[0093] The cyclic voltammogram of compound 3 in 1M KCl solution is shown below. Figure 4 As shown in the figure. The results indicate that this compound exhibits good redox properties under neutral conditions. E 1 / 2 =-0.31V (vs SHE), ΔE=160mV.

[0094] Test Example 4: Cyclic Voltammetry Test (Compound 4)

[0095] Cyclic voltammetry was performed using a three-electrode system. The working electrode was a 3mm glassy carbon electrode, the reference electrode was an aqueous Ag / AgCl electrode, and the counter electrode was a platinum mesh electrode. The voltage scan range was -0.7V to 1.2V, and the scan rate was 20mV / s.

[0096] The cyclic voltammogram of compound 4 in 1M NaCl solution is shown below. Figure 5 As shown in the figure. The results indicate that this compound exhibits good redox properties under neutral conditions. E 1 / 2 =-0.11V (vs SHE), ΔE=60mV.

[0097] Test Example 5: Current Cycling Test (Compound 1)

[0098] Constant current and constant current-constant voltage charge-discharge cycle tests were performed using an electrochemical workstation. A battery was assembled using Compound 1, employing an NC700 cation exchange membrane and ELAT carbon cloth as the electrode material. During the constant current phase, the charge-discharge current was 100 mA, and the current density was 20 mA / cm². 2 The constant voltage stage has a voltage range of 1.3V-0.4V and a cutoff current of 20mA.

[0099] During low-concentration battery cycling, the negative electrode solution consisted of 5.0 mL of 0.1 M compound 1 dissolved in 1.0 M KCl solution; the positive electrode solution consisted of 40.0 mL of 0.1 M K4Fe(CN)6 and 0.02 M K3Fe(CN)6 dissolved in 1.0 M KCl solution.

[0100] The test results of 0.1M compound 1 in 1.0M KCl solution are as follows: Figure 6 and 7 As shown, a constant current cycle test of 626 cycles (13.5 days) was first conducted, and no capacity loss was observed. Then, a constant current and constant voltage charge-discharge test was conducted for a total of 2513 cycles (54.4 days), with a battery capacity decay of 0.00008% / cycle. During the constant current phase, the actual capacity utilization was 97% of the theoretical capacity. With the constant voltage phase, the capacity utilization increased to 98%, and the coulombic efficiency reached 100%.

[0101] During the high-concentration battery cycle, the negative electrode solution consists of 5.0 mL of 0.7 M compound 1 dissolved in H2O solution; the positive electrode solution consists of 80.0 mL of 0.4 M K4Fe(CN)6 and 0.1 M K3Fe(CN)6 dissolved in H2O.

[0102] The test results of 0.7M compound 1 in water are as follows: Figure 8 and 9 As shown. First, a constant current cycle test of 152 cycles (23.2 days) was conducted, with a battery capacity decay of 0.0039% per cycle. Then, a constant current and constant voltage charge-discharge test was conducted for a total of 250 cycles (38.7 days), with a battery capacity decay of 0.0041% per cycle. The actual capacity utilization reached 98% of the theoretical capacity, and the coulombic efficiency reached 100%.

[0103] All documents mentioned in this invention are incorporated herein by reference as if each document were individually incorporated by reference. Furthermore, it should be understood that after reading the foregoing teachings of this invention, those skilled in the art can make various alterations or modifications to this invention, and these equivalent forms also fall within the scope defined by the appended claims.

Claims

1. A compound selected from the group consisting of, or a salt thereof formed with a charge-balancing ion: 。 2. A method for preparing the compound as described in claim 1, or optionally the compound by losing a H atom, or the salt thereof formed with a charge-balancing ion, characterized in that, The method includes the following steps: An electrochemical workstation was constructed using a KCl solution containing the free radical cations of compound 5 or 6 as the positive electrode electrolyte and ZnCl2 as the negative electrode electrolyte. Constant current and constant voltage charge-discharge cycles were performed, and the positive electrode electrolyte was separated after cycling to obtain the aforementioned compound, or alternatively, the compound that has lost H+. + or its salts with charge-balancing ions: or .

3. A flow battery energy storage material, characterized in that, The flow battery energy storage material is prepared using the compound as described in claim 1 as the active ingredient.

4. A flow battery, characterized in that, The flow battery described herein includes the compound as described in claim 1 as an energy storage material.

5. The flow battery as described in claim 4, characterized in that, In the flow battery described above, the compound as described in claim 1 is used as the negative electrode or positive electrode solution.

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