Aqueous flow battery energy storage material based on phenazine resonance hybrid

Abstract

The invention provides an aqueous flow battery energy storage material based on a phenazine resonance hybrid, and particularly provides a phenazine resonance hybrid compound which can be used as the aqueous flow battery energy storage material. The preparation method of the compound is simple, and the prepared battery energy storage material has relatively good cycling stability and energy efficiency and is suitable for being used as an energy storage material of an aqueous flow battery.

Description

Technical Field

[0001] The present invention belongs to the field of synthesis of polysubstituted phenazine resonance hybrid energy storage materials and aqueous liquid flow battery energy storage technology, and specifically relates to a synthesis method of several polysubstituted phenazine derivative resonance hybrids with redox activity, and their application in aqueous liquid flow battery energy storage systems. Background Art

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

[0003] Organic molecules have great potential for application in ARFBs, which may lead to a significant reduction in the levelized cost of energy storage. Compared with inorganic molecules, organic molecules have inherent advantages due to their structural diversity and adjustability, as well as raw materials based on elements that are abundant on Earth. These properties help optimize battery performance and promote the sustainability of energy storage technologies. Although in theory, any organic compound that can undergo reversible redox reactions can be a candidate for active materials in aqueous organic redox flow batteries (AORFBs), only a limited number of organics have been demonstrated to be promising energy storage materials. However, most of them have high capacity decay rates. One major reason is that water can undergo nucleophilic addition reactions or substitution reactions, such as Michael addition reactions and hydrolysis reactions, which greatly affect the long-term cycling performance of the battery. Therefore, it is crucial to develop stable organic reduction active materials that can work effectively in complex electrochemical environments.

[0004] In order to mitigate water-induced degradation reactions within a certain pH range, larger conjugated systems have been shown to have higher stability, such as extending benzoquinone to anthraquinone and pyrazine to phenazine. However, the electron density of the expanded large conjugated aromatic system in the reduced state is higher than that in its oxidized state. In order to achieve a more stable and lower energy configuration, the molecule will undergo structural reorganization between or within the molecule to achieve electron redistribution, and finally exist in the most stable low-energy state, which is the driving force for the spontaneous occurrence of side reactions. Therefore, it is crucial to develop strongly conjugated organic redox systems, through directional induction, so that the molecules have appropriate electron density in the process of gaining and losing electrons to suppress the attack of water or other nucleophiles, while avoiding side reactions such as isomerization caused by excessive electron density. Redistribution of electrons is crucial for promoting stable AORFBs.

[0005] Therefore, there is an urgent need in the art to provide a new type of aqueous liquid flow battery energy storage material. Summary of the invention

[0006] The present invention designs and synthesizes a series of stable multi-substituted phenazine compounds based on the phenazine structure. The synthesis of resonance hybrids is achieved by adjusting the substituents, and the potential and solubility can be regulated at the same time. The new skeleton designed by the resonance strategy can greatly improve the stability of the reduced or oxidized state of the compound. The strategy of combining chemical synthesis with electrochemical synthesis reduces the difficulty of synthesis and simplifies the synthesis steps. Using non-corrosive and non-flammable pH neutral aqueous solution and cheap inorganic salts as supporting electrolytes has the advantages of high safety, low corrosion, low cost, and environmental friendliness. The results of battery cycling show that such compounds have high concentration and long cycle stability in aqueous flow batteries.

[0007] In a first aspect of the present invention, there is provided a compound as shown in the following formula, or a salt thereof which optionally loses an H atom, or is formed with a charge-balancing ion:

[0008]

[0009] Wherein, Z and E may be the same or different and are independently selected from the group consisting of 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 are each independently selected from the following group: H, halogen, substituted or unsubstituted C1-C10 alkyl, C3-C8 cycloalkyl, 3-8 membered heterocyclic group, substituted or unsubstituted C6-C10 aryl, hydroxyl, thiol, amine, 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 10are each independently selected from the following group: H, substituted or unsubstituted C1-C10 alkyl; or R 9 , R 10 and the carbon atoms connected thereto together constitute a group selected from the group consisting of a C3-C8 cycloalkyl group, a 3-8 membered heterocyclic group;

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

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

[0016] X is selected from the following group: H + NH4 + , Li + 、Na + , K + Mg 2+ 、Al 3+ , Ca 2+ ;M - Select 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 following group: + NH4 + , Li + 、Na + , K + Mg2+ 、Al 3+ , Ca 2+ ; The anion or M - Select 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 - ; and the compound is electrically neutral;

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

[0019] In another preferred embodiment, when R 2 , R 3 , R 6 , R 7 Each independently selected from CH2 - ,NH - ,O - ,SiH2 - ,PH - ,S - When, 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 8, R are each independently selected from the following group: H, halogen, C1-C6 alkyl, hydroxyl, thiol, amine, carboxyl, phosphate, sulfonic acid, or

[0022] Wherein, Y is a chemical bond, O or S;

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

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

[0025] R 0 Selected from the following group: -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 are independently selected from the following group: 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 is independently selected from the following group: H, halogen, C1-C6 alkyl, hydroxyl, thiol, amine, carboxyl, phosphate, sulfonic acid; R is Where k is 2, 3, 4 or 5; R 0 Selected from the following group: R 0 Selected from the following group: -COOX, -SO3X, -N + (CH3)3M - ;M - Select 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 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 Selected from the following group: -COOX, -SO3X, -N + (CH3)3M - ;M - Select from the following group: F - , Cl - Br - ,I - , CN - .

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

[0030]

[0031] The second aspect of the present invention provides a method for preparing the compound as described in the first aspect of the present invention, or a salt thereof which optionally loses an 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 is formed by using a KCl solution of a free radical cation represented by Formula I as a positive electrode electrolyte and ZnCl2 as a negative electrode electrolyte, and constant current and constant voltage charging and discharging are performed. After the cycle, the positive electrode electrolyte is separated to obtain the compound, or it optionally loses H + , or its salts with charge-balancing ions:

[0033]

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

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

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

[0037] It should be understood that within the scope of the present invention, the above-mentioned technical features of the present invention and the technical features specifically described below (such as embodiments) can be combined with each other to form a new or preferred technical solution. Due to space limitations, they will not be described one by one here. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 is the single crystal structure diagram of compound 1;

[0039] Figure 2 is the cyclic voltammogram of compound 1 in 1.0 M KCl solution;

[0040] Figure 3 is the cyclic voltammogram of compound 2 in 1.0 M KCl solution;

[0041] Figure 4 is the cyclic voltammogram of compound 3 in 1.0 M KCl solution;

[0042] Figure 5 is the cyclic voltammogram of compound 4 in 1.0 M KCl solution;

[0043] Figure 6 and Figure 7 The charge-discharge cycle test results of 0.1M compound 1 in 1M KCl solution;

[0044] Figure 8 and Fig. 9 The charge-discharge cycle test results of 0.7M compound 1 in H2O solution. DETAILED DESCRIPTION

[0045] After long-term and in-depth research, the inventors have developed a compound that can be used as an energy storage material for aqueous liquid flow batteries. The preparation method of the compound is simple, and the prepared battery energy storage material has good cycle stability and energy efficiency. Based on the above findings, the inventors have completed the present invention.

[0046] the term

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

[0048] In the present 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 the present invention, the term "alkyl" refers to a saturated linear or branched hydrocarbon moiety. For example, the term "C1-C10 alkyl" refers to a straight or branched alkyl group having 1 to 10 carbon atoms, including but not limited to methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl, pentyl and hexyl, etc.; preferably ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl and tert-butyl.

[0050] In the present invention, the term "aryl" or "aromatic ring" refers to a hydrocarbon moiety containing one or more aromatic rings. Examples of aryl groups include, but are not limited to, phenyl (Ph), naphthyl, pyrenyl, fluorenyl, anthracenyl, and phenanthrenyl.

[0051] In the present invention, the term "heteroaryl" refers to a moiety containing one or more aromatic rings having at least one heteroatom, such as N, O or S. Examples of heteroaryl groups include furanyl, pyrrolyl, thienyl, oxazolyl, imidazolyl, thiazolyl, pyridyl, pyrimidinyl, quinazolinyl, quinolyl, isoquinolyl and indolyl, etc.

[0052] Flow Battery

[0053] In a flow battery, the positive and negative electrolytes are stored in external storage tanks respectively and transported to the battery stack through a peristaltic pump. The active substances undergo redox reactions on the electrode surface to achieve energy storage and release. Compared with traditional chemical batteries such as lithium-ion batteries, flow batteries have the advantage that energy and power are independent of each other, that is, the energy depends on the concentration and volume of the energy storage material, while the power depends on the electrode area. When the scale of energy storage is larger, the cost of this technology is closer to the cost of the energy storage material, so although lithium-ion batteries have a higher energy density, flow batteries are more suitable for large-scale energy storage power stations. According to the type of solvent used in the electrolyte, flow batteries are divided into aqueous flow batteries and non-aqueous (organic solvent) flow batteries.

[0054] Aqueous flow batteries are divided into aqueous inorganic flow batteries and aqueous organic flow batteries according to whether the energy storage materials used are inorganic or organic. At present, the most studied and widely used energy storage materials are all inorganic materials. However, the high cost and limited resources of inorganic materials, the easy formation of dendrites during use, and the slow electrochemical reaction rate limit the large-scale application of inorganic flow batteries. Using organic matter as an energy storage material, its source is more extensive than the limited metals stored in the earth's crust, the cost of use is lower, and it can reduce the pollution of heavy metals to the environment. Compared with inorganic materials, organic materials have the advantages of light weight, low price, ductility and plasticity; the electrochemical reaction rate of organic materials is faster, usually 1-2 orders of magnitude higher than that of inorganic metals, without the use of catalysts, and will not form dendrites to damage the diaphragm; at the same time, synthetic chemists can modify and functionalize them at the molecular level, and optimize the solubility and redox potential of organic materials by introducing functional groups, thereby adjusting the energy density and open circuit voltage of the battery. Therefore, studying the structural characteristics, electrochemical properties and possible degradation mechanisms of organic energy storage materials to improve the performance, energy density and life of aqueous organic flow batteries while reducing their costs 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 in human production activities.

[0055] Flow battery energy storage materials

[0056] The present invention provides a compound that can be used as an organic energy storage material for an aqueous flow battery, or a salt thereof that optionally loses an H atom or forms with a charge-balancing ion. Specifically, the compound has the structure shown below:

[0057]

[0058] Wherein, Z and E may be the same or different and are independently selected from the group consisting of 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 are each independently selected from the following group: H, halogen, substituted or unsubstituted C1-C10 alkyl, C3-C8 cycloalkyl, 3-8 membered heterocyclic group, substituted or unsubstituted C6-C10 aryl, hydroxyl, thiol, amine, carboxyl, phosphate, sulfonic acid, or the following water-soluble groups:

[0061] Wherein, Y is a chemical bond, 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 are each independently selected from the following group: H, substituted or unsubstituted C1-C10 alkyl; or R 9 , R 10 and the carbon atoms connected thereto together constitute a group selected from the group consisting of a C3-C8 cycloalkyl group, a 3-8 membered heterocyclic group;

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

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

[0065] X is selected from the following group: H + NH4 + , Li + 、Na + , K + Mg 2+ 、Al 3+ , Ca 2+ ;M - Select 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 following group: + NH4 + , Li + 、Na + , K + Mg 2+ 、Al 3+ , Ca 2+ ; The anion or M - Select 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 - ; and the compound is electrically neutral;

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

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

[0069]

[0070] It should be understood that since the above compounds are charge balanced, several H + ions, or form electrically neutral compounds with several conventional cations or anions, such forms do not affect the achievement of the purpose of the present invention.

[0071] The present invention will be further described below in conjunction with specific examples. It should be understood that these examples are only used to illustrate the present invention and are not intended to limit the scope of the present invention. The experimental methods in the following examples without specifying specific conditions are usually based on conventional conditions or the conditions recommended by the manufacturer. Unless otherwise stated, percentages and parts are calculated by weight.

[0072] Example (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 1 M KCl solution to prepare a 0.2 M positive electrode electrolyte, and ZnCl2 was dissolved in 100 mL 1 M KCl solution to prepare a 0.2 M negative electrode electrolyte. Nafion 212 cation exchange membrane and AvCarb Felt G100 carbon felt were used as electrode materials. A flow battery was used for cycle testing. An electrochemical workstation was used for constant current and constant voltage charging and discharging, with a cut-off voltage of 2.2 V to 0.9 V. After 16 hours of circulation, the positive electrode electrolyte was separated and purified by a reverse phase column, and 2.4 g of the target product 1 (red solid) was obtained with a yield of 76%, and 198 mg of the target product 2 was obtained with a yield of 7%.

[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 30mL 1M KCl solution to prepare a 0.2M positive electrolyte, and ZnCl2 was dissolved in 100mL 1M KCl solution to prepare a 0.2M negative electrolyte. Huamo Technology's anion exchange membrane, AvCarb Felt G100 carbon felt was used as the electrode material. Constant current and constant voltage charging and discharging were performed using an electrochemical workstation, with a cut-off voltage of 2.4V-1.0V. After 16 hours of circulation, the positive electrolyte was separated and purified by a reverse phase column, and 1.0g of the target product 3 (red solid) was obtained with a yield of 30%, and 1.0g of the target product 4 was obtained with a yield of 30%.

[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] The cyclic voltammetry test uses a three-electrode system. The working electrode is a 3mm glassy carbon electrode, the reference electrode is aqueous Ag / AgCl, and the counter electrode is a platinum mesh electrode. The voltage scanning range during the test is: -0.6V~-0.1V, and the scanning rate is 20mV / s.

[0087] Cyclic voltammogram of test compound 1 in 1M KCl solution, as shown in Figure 2 The results show that the compound can exhibit good redox performance under neutral conditions. 1 / 2 =-0.36V (vs SHE), ΔE=130mV.

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

[0089] The cyclic voltammetry test uses a three-electrode system. The working electrode is a 3mm glassy carbon electrode, the reference electrode is aqueous Ag / AgCl, and the counter electrode is a platinum mesh electrode. The voltage scanning range during the test is: -0.8V~0.2V, and the scanning rate is 20mV / s.

[0090] Cyclic voltammogram of test compound 2 in 1M KCl solution, as shown in Figure 3 The results show that the compound can exhibit good redox performance under neutral conditions. 1 / 2 =-0.18V (vs SHE), ΔE=70mV.

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

[0092] The cyclic voltammetry test uses a three-electrode system. The working electrode is a 3mm glassy carbon electrode, the reference electrode is aqueous Ag / AgCl, and the counter electrode is a platinum mesh electrode. The voltage scanning range during the test is: -0.7V~1.2V, and the scanning rate is 20mV / s.

[0093] Cyclic voltammogram of test compound 3 in 1M KCl solution, as shown in Figure 4 The results show that the compound can exhibit good redox performance under neutral conditions. 1 / 2 =-0.31V (vs SHE), ΔE=160mV.

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

[0095] The cyclic voltammetry test uses a three-electrode system. The working electrode is a 3mm glassy carbon electrode, the reference electrode is aqueous Ag / AgCl, and the counter electrode is a platinum mesh electrode. The voltage scanning range during the test is: -0.7V~1.2V, and the scanning rate is 20mV / s.

[0096] Cyclic voltammogram of test compound 4 in 1 M NaCl solution, as shown in Figure 5 The results show that the compound can exhibit good redox performance under neutral conditions. 1 / 2 =-0.11V (vs SHE), ΔE=60mV.

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

[0098] The constant current and constant current constant voltage charge and discharge cycle tests were performed using an electrochemical workstation. The battery was assembled with compound 1, using NC700 cation exchange membrane and ELAT carbon cloth as electrode materials. The charge and discharge current in the constant current stage was 100 mA, and the current density was 20 mA / cm 2 ,The voltage range in the constant voltage stage is 1.3V-0.4V, and the cut-off current is 20mA.

[0099] During the low-concentration battery cycling process, the negative electrode solution was 5.0 mL of 0.1 M compound 1 dissolved in 1.0 M KCl solution; the positive electrode solution was 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 was first performed for 626 cycles (13.5 days), and no capacity loss was observed. Then a constant current and constant voltage charge and discharge test was performed for a total of 2513 cycles (54.4 days), and the battery capacity decayed by 0.00008% / cycle. The actual capacity in the constant current stage accounted for 97% of the theoretical capacity. After the constant voltage was added, the capacity utilization rate increased to 98%, and the coulomb efficiency could reach 100%.

[0101] During the high-concentration battery cycling process, the negative electrode solution was 5.0 mL of 0.7 M compound 1 dissolved in H2O solution; the positive electrode solution was 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 was performed for 152 cycles (23.2 days), and the battery capacity decayed by 0.0039% / cycle. Then, a constant current and constant voltage charge and discharge test was performed for a total of 250 cycles (38.7 days), and the battery capacity decayed by 0.0041% / cycle. The actual capacity accounted for 98% of the theoretical capacity, and the coulomb efficiency could reach 100%.

[0103] All documents mentioned in the present invention are cited as references in this application, just as each document is cited as reference individually. In addition, it should be understood that after reading the above teachings of the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the claims attached to this application.

Claims

1. A compound as shown in the following formula, or a salt thereof which optionally loses an H atom, or forms with a charge-balancing ion: Wherein, Z and E may be the same or different and are independently selected from the group consisting of N, P, PO, As, Sb, O, S, SO, SO2, Se or Te; m and n are each independently 0 or 1; R 1 , R 2 , R 3 , R 4 , R 5 , R 6 , R 7 , R 8 , R are each independently selected from the following group: H, halogen, substituted or unsubstituted C1-C10 alkyl, C3-C8 cycloalkyl, 3-8 membered heterocyclic group, substituted or unsubstituted C6-C10 aryl, hydroxyl, thiol, amine, carboxyl, phosphate, sulfonic acid, or the following water-soluble groups: in, 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; R 9 , R 10 Each is independently selected from the following group: H, substituted or unsubstituted C1-C10 alkyl; or R 9 , R 10 and the carbon atoms connected thereto together constitute a group selected from the group consisting of a C3-C8 cycloalkyl group, a 3-8 membered heterocyclic group; k is selected from the group consisting of 1, 2, 3, 4, 5, 6, 7, 8; R 0 Selected from the following group: -COOX, -SO3X, -PO3X, -NH2·HQ, -NHCH3·HQ, -N(CH3)2·HQ, -N + (CH3)3M - ; Q is selected from the following group: Cl - , SO4 2- ; X is selected from the following group: H + NH4 + , Li + 、Na + , K + Mg 2+ 、Al 3+ , Ca 2+ ;M - Select 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; The charge-balancing ion is a cation or anion, and the cation is selected from the following group: + NH4 + , Li + 、Na + , K + Mg 2+ 、Al 3+ , Ca 2+ ; The anion or M - Select 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 - ; and the compound is electrically neutral; The substitution refers to that one or more hydrogen atoms on the group are replaced by a substituent selected from the following group: halogen, C1-C6 alkyl, C6-C10 aryl, hydroxyl, thiol group, amine group, carboxyl group, phosphate group, sulfonic acid group; the heteroatom in the heterocyclic group is N, O or S. In another preferred embodiment, when R 2 , R 3 , R 6 , R 7 Each independently selected from CH2 - ,NH - ,O - ,SiH2 - ,PH - ,S - When, the general formula has the following resonance form:

2. A compound as claimed in claim 1, or optionally a compound which has lost an H atom, or a salt thereof with a charge-balancing ion, characterized in that The R 1 , R 2 , R 3 , R 4 , R 5 , R 6 , R 7 , R 8 , R are each independently selected from the following group: H, halogen, C1-C6 alkyl, hydroxyl, thiol, amine, carboxyl, phosphate, sulfonic acid, or Wherein, Y is a chemical bond, O or S; R 9 , R 10 Each independently selected from the group consisting of: H, C1-C4 alkyl; k is selected from the group consisting of 1, 2, 3, 4, 5, 6, 7, 8; R 0 Selected from the following group: -COOX, -SO3X, -PO3X, -NH2·HQ, -NHCH3·HQ, -N(CH3)2·HQ, -N + (CH3)3M - .

3. A compound as claimed in claim 1, or a salt thereof which optionally loses an H atom, or a salt thereof with a charge-balancing ion, characterized in that The Z and E may be the same or different, and are each independently selected from the following group: N or P.

4. A compound as claimed in claim 1, or a salt thereof which optionally loses an H atom, or a salt thereof with a charge-balancing ion, characterized in that 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, halogen, C1-C6 alkyl, hydroxyl, thiol, amine, carboxyl, phosphate, sulfonic acid; R is Where k is 2, 3, 4 or 5; R 0 Selected from the following group: R 0 Selected from the following group: -COOX, -SO3X, -N + (CH3)3M - ;M - Select from the following group: F - , Cl - Br - ,I - , CN - .

5. A compound as claimed in claim 1, or a salt thereof which optionally loses an H atom, or a salt thereof with a charge-balancing ion, characterized in that The R 1 , R 2 , R 3 , R 4 , R 5 , R 6 , R 7 , R 8 Each 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 Selected from the following group: -COOX, -SO3X, -N + (CH3)3M - ;M - Select from the following group: F - , Cl - Br - ,I - , CN - .

6. A compound as claimed in claim 1, or a salt thereof which optionally loses an H atom, or a salt thereof with a charge-balancing ion, characterized in that The compound is selected from the following group:

7. A method for preparing a compound as claimed in claim 1, or a compound optionally losing an H atom thereof, or a salt thereof with a charge-balancing ion, characterized in that: The method comprises the steps of: An electrochemical workstation is formed by using a KCl solution of a free radical cation represented by Formula I as a positive electrode electrolyte and ZnCl2 as a negative electrode electrolyte, and constant current and constant voltage charging and discharging are performed. After the cycle, the positive electrode electrolyte is separated to obtain the compound, or it optionally loses H + , or its salts with charge-balancing ions:

8. A liquid flow battery energy storage material, characterized in that: The liquid flow battery energy storage material is prepared using the compound described in any one of claims 1 to 6 as an active ingredient.

9. A liquid flow battery, characterized in that: The liquid flow battery comprises the compound as described in any one of claims 1 to 6 as an energy storage material.

10. The flow battery according to claim 9, characterized in that In the liquid flow battery, the compound described in any one of claims 1 to 6 is used as the negative electrode or positive electrode solution.

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