Negative Electrolyte and its Preparation Method, and Aqueous Organic Flow Battery

Abstract

This invention relates to a negative electrode electrolyte, its preparation method, and an aqueous organic flow battery. The negative electrode electrolyte comprises a negative electrode active material, a supporting electrolyte, and a solvent; wherein the negative electrode active material has the structure shown in formula (1): (1) where R represents H, -NH2, -OH, -CHO, -COOH, -PO3H2, or -SO3H. The negative electrode electrolyte of this invention uses a specific negative electrode active material to effectively block key side reactions (such as Michael addition) that lead to failure from the intrinsic structure of the negative electrode active material, thereby significantly improving the cycle life and capacity retention of the battery without the need for complex artificial synthesis modifications.

Description

Technical Field

[0001] This invention relates to a negative electrode electrolyte and its preparation method, as well as an aqueous organic flow battery, belonging to the field of electrochemical energy storage technology. Background Technology

[0002] Aqueous flow batteries, with their inherent safety, environmental friendliness, and ease of large-scale deployment, are considered a promising and important technological route to meet the long-term energy storage needs of the grid and industrial and commercial sectors. Currently, mainstream vanadium redox flow batteries (VRFBs) have advantages over organic redox flow batteries (AORFBs) in terms of the wide availability of active electrolyte raw materials, the ability to design molecular structures, and significant advantages in system cost control, making them a strong contender for next-generation green energy storage technology.

[0003] Among various organic active molecules, quinones possess reversible multi-electron / proton redox properties and exhibit rapid electrode reaction kinetics, theoretically enabling higher power density and energy efficiency. They are considered ideal anode materials for constructing high-performance organic redox flow batteries. Current technologies primarily rely on molecular engineering strategies to modify quinone molecules, introducing specific functional groups (such as sulfonic acid groups and phosphonic acid groups to improve water solubility, or hydroxyl and amino groups to regulate redox potential) onto aromatic rings or side chains to optimize their electrochemical performance. Unfortunately, the poor chemical and electrochemical stability of quinone active materials during long-cycle cycling remains a core bottleneck restricting their commercialization.

[0004] In theory, quinone-based flow batteries have great potential in long-term energy storage, but in practical applications they are often constrained by the following three major problems:

[0005] 1. Inherent safety hazards of replacing active materials in the positive electrode. The use of quinones in the positive electrode is often unstable and inevitably leads to side reactions such as Michael addition. Therefore, current technologies generally employ a "semi-quinone system," where the positive electrode uses ferrocyanide Fe(CN)6 from an alkaline system. 3- / Fe(CN)6 4- Or Br in acidic systems - / Br2. Although Fe(CN)6 is used. 3- / Fe(CN)6 4- and Br -The Br2 system can improve the electrochemical performance and cycle stability of organic redox flow batteries to some extent, but both of these approaches have insurmountable drawbacks that significantly limit the system's safety and long lifespan. ① Ferrocyanide system: Under alkaline or high-concentration conditions, it easily generates insoluble Prussian blue analogues, leading to electrode surface passivation, blocked flow channels, increased internal resistance, and capacity decay, requiring frequent replacement of electrolyte materials. ② Bromine system: Involves highly corrosive and volatile free bromine, placing extremely high demands on battery piping and sealing materials. Furthermore, the severe transmembrane cross-linking of bromine molecules easily triggers unilateral self-discharge, resulting in a significant decrease in coulombic efficiency and posing serious safety hazards.

[0006] 2. Side effects of chemical additives. To suppress side reactions of quinone molecules (such as Michael addition and disproportionation), existing technologies attempt to add solid additives (such as carbon black), polymers, or inorganic salt stabilizers to the electrolyte. While these additives have slowed capacity decay to some extent, they have also introduced new technical problems. For example: ① Membrane fouling and increased resistance: Additives are easily adsorbed by ion exchange membranes or cause membrane pore blockage, leading to a significant increase in membrane resistance and local swelling, thus reducing voltage efficiency. ② Limited energy density and kinetics: The introduction of solid additives occupies the effective volume of the electrolyte, reducing the system's volumetric energy density. Simultaneously, some additives have slow reaction rates at low state of charge (SOC), limiting the battery's rate performance.

[0007] 3. Artificial synthesis modification is costly and complex. Regarding the stability of the quinone molecule core—especially the irreversible Michael addition reaction—the most mainstream solution currently is to artificially modify it by introducing blocking groups (such as sulfonic acid groups, methyl groups, phosphonic acid groups, etc.) at specific sites (such as the β-position) of the quinone ring through complex organic synthesis. However, this "molecular engineering"-based synthetic route is often cumbersome and requires harsh reaction conditions, resulting in high raw material preparation costs. Although existing technologies have demonstrated the stability of certain structures (such as methylated quinones) through calculations, they largely rely on expensive chemically synthesized products. Currently, there is a lack of naturally occurring, inexpensive, and inherently Michael addition-resistant active molecules on the market that do not require complex synthesis.

[0008] It is evident that most of the quinone-based active materials used in existing organic redox flow batteries have inherent structural defects, making them prone to side reactions such as Michael addition. This results in chemical instability, rapid capacity decay, and unsuitability for long-term energy storage scenarios. Furthermore, the artificial synthesis modification strategies employed to improve stability face technical bottlenecks such as high cost and complex processes.

[0009] In summary, although existing technologies attempt to mitigate the problem through engineering methods such as full-site substitution, membrane material screening, and electrolyte optimization, there is still a lack of an ideal quinone anode material that combines high intrinsic stability (especially resistance to Michael addition), simple synthesis, abundant sources, and environmental friendliness. Summary of the Invention

[0010] The problem the invention aims to solve

[0011] Quinone molecules face various failure risks in battery operating environments. Given the technical problems existing in current technologies, such as: ① Deactivation due to chemical side reactions: Under specific pH conditions, quinone molecules are prone to disproportionation reactions and subsequent dimerization or polymerization; especially the nucleophilic addition reaction at the β-position of the quinone ring (Michael addition), which directly leads to irreversible damage and permanent deactivation of the molecular skeleton; ② Decay in physical and electrochemical performance: Potential drift induced by possible tautomerism and side reactions of active molecules, as well as insoluble precipitation caused by structural instability, not only lead to continuous capacity decay but also cause increased internal resistance, flow channel or electrode blockage, significantly increasing the system's maintenance burden; ③ Transmembrane permeation and accumulation of side reactions: Transmembrane permeation of active materials leads to electrolyte composition imbalance and self-discharge, further affecting coulombic efficiency and long-term cycle retention, etc.; This invention first provides a negative electrode electrolyte.

[0012] The negative electrode electrolyte of the present invention uses specific negative electrode active materials to effectively block key side reactions (such as Michael addition) that lead to failure from the intrinsic structure of the negative electrode active materials, thereby significantly improving the cycle life and capacity retention of the battery without the need for complex artificial synthesis and modification.

[0013] Furthermore, the negative electrode active material of this invention has the advantages of being widely available and renewable, solving the problems of high cost and difficult preparation of existing high-performance organic energy storage materials, and realizing low-cost, highly safe and environmentally friendly long-term energy storage.

[0014] Furthermore, the present invention also provides a method for preparing a negative electrode electrolyte, which is simple and easy to implement, uses readily available raw materials, and is suitable for mass production.

[0015] Furthermore, this invention also provides an aqueous organic flow battery. The aqueous organic flow battery of this invention exhibits significant advantages in electrochemical kinetics and intrinsically high energy characteristics. Without the addition of any chemical stabilizers, emodin, due to its intrinsic structural advantages, achieves high energy density, high power, and high efficiency, with a charge-discharge energy efficiency of over 95%.

[0016] Solution for solving the problem

[0017] [1] A negative electrode electrolyte, wherein the negative electrode electrolyte comprises a negative electrode active material, a supporting electrolyte, and a solvent; wherein,

[0018] The negative electrode active material has the structure shown in formula (1):

[0019] (1)

[0020] Where R represents H, -NH2, -OH, -CHO, -COOH, -PO3H2, or -SO3H.

[0021] [2] According to the negative electrode electrolyte described in [1] above, wherein the supporting electrolyte in the negative electrode electrolyte includes an alkaline substance.

[0022] [3] The negative electrode electrolyte according to [1] or [2] above, wherein the alkaline substance includes KOH or NaOH.

[0023] [4] The negative electrode electrolyte according to any one of [1]-[3] above, wherein the concentration of the negative electrode active material in the negative electrode electrolyte is 0.005~0.2 mol / L and the concentration of the supporting electrolyte is 0.5-1.5 mol / L.

[0024] [5] The negative electrode electrolyte according to any one of [1]-[4] above, wherein the solvent is water.

[0025] [6] A method for preparing a negative electrode electrolyte according to any one of [1]-[5] above, comprising the step of mixing a negative electrode active material, a supporting electrolyte and a solvent.

[0026] [7] An aqueous organic flow battery, comprising a positive electrode, a negative electrode and a separator, wherein the negative electrode comprises a negative electrode electrolyte according to any one of [1]-[5] above.

[0027] [8] According to the aqueous flow battery described in [7] above, the positive electrode includes a positive electrolyte, which includes a positive active material, a supporting electrolyte, and a solvent.

[0028] [9] According to the aqueous flow battery described in [8] above, the positive electrode active material includes soluble ferrocyanate and / or 2,5-dihydroxybenzenesulfonic acid.

[0029]

[10] According to the aqueous flow battery described above [9], the soluble ferrocyanate includes one or two of potassium ferrocyanide and sodium ferrocyanide.

[0030] The effects of the invention

[0031] The negative electrode electrolyte of the present invention uses specific negative electrode active materials to effectively block key side reactions (such as Michael addition) that lead to failure from the intrinsic structure of the negative electrode active materials, thereby significantly improving the cycle life and capacity retention of the battery without the need for complex artificial synthesis and modification.

[0032] Furthermore, the negative electrode active material of this invention has the advantages of being widely available and renewable, enabling low-cost, highly safe, and environmentally friendly long-term energy storage.

[0033] Furthermore, the preparation method of the negative electrode electrolyte of the present invention is simple and easy to implement, the raw materials are readily available, and it is suitable for mass production.

[0034] Furthermore, the aqueous organic flow battery of the present invention exhibits significant electrochemical kinetic advantages and intrinsic high energy characteristics. Without the addition of any chemical stabilizers, emodin, due to its intrinsic structural advantages, achieves high energy density, high power, and high efficiency, with a charge-discharge energy efficiency of over 95%. Attached Figure Description

[0035] Figure 1 The battery cycle performance of the flow battery systems of Examples 1-4 of the present invention is shown.

[0036] Figure 2 The following are liquid chromatograms of the negative electrode electrolyte of Embodiment 1 of the present invention before and after charge-discharge cycles, where a is before cycling and b is after cycling. Detailed Implementation

[0037] Various exemplary embodiments, features, and aspects of the present invention will be described in detail below. The term "exemplary" as used herein means "serving as an example, embodiment, or illustration." Any embodiment described herein as "exemplary" is not necessarily to be construed as superior to or better than other embodiments.

[0038] Furthermore, to better illustrate the present invention, numerous specific details are set forth in the following detailed embodiments. Those skilled in the art should understand that the present invention can be practiced without certain specific details. In other instances, methods, means, apparatus, and steps well known to those skilled in the art have not been described in detail in order to highlight the spirit of the present invention.

[0039] Unless otherwise stated, all units used in this specification are international standard units, and all numerical values ​​and ranges appearing in this invention should be understood to include systematic errors that are unavoidable in industrial production.

[0040] In this specification, the word "may" has two meanings: to perform a certain process and not to perform a certain process.

[0041] In this specification, references to "some specific / preferred embodiments," "other specific / preferred embodiments," "implementation," etc., refer to specific elements (e.g., features, structures, properties, and / or characteristics) related to that embodiment, which are included in at least one of the embodiments described herein and may or may not be present in other embodiments. Furthermore, it should be understood that these elements may be combined in any suitable manner in various embodiments.

[0042] In this specification, the range of values ​​referred to as "value A to value B" refers to the range including the endpoint values ​​A and B.

[0043] <First Aspect>

[0044] A first aspect of the present invention provides a negative electrode electrolyte, wherein the negative electrode electrolyte comprises a negative electrode active material, a supporting electrolyte, and a solvent; wherein,

[0045] The negative electrode active material has the structure shown in formula (1):

[0046] (1)

[0047] Where R represents H, -NH2, -OH, -CHO, -COOH, -PO3H2, or -SO3H.

[0048] When R represents H, the negative electrode active material of this invention is the natural product emodin (1,3,8-trihydroxy-6-methylanthraquinone), which can be extracted on a large scale from traditional Chinese medicinal plants such as rhubarb and Polygonum cuspidatum, or it can be purchased commercially. It is inexpensive, with the raw material costing only 1 / 5 to 1 / 10 of that used to synthesize quinones. Furthermore, emodin is a pharmaceutical intermediate with a stable supply. Compared to scarce or high-risk materials such as vanadium and bromine, it is renewable, non-toxic, and easy to store, thus avoiding resource bottlenecks and safety risks. The negative electrode active material of this invention can be purchased commercially or prepared in-house.

[0049] Furthermore, the inventors of this invention discovered that even when introducing typical functional groups with different electronic effects (including electron-donating and electron-withdrawing properties) such as -NH2 (amino), -OH (hydroxyl), -CHO (aldehyde), -COOH (carboxyl), -PO3H2 (phosphate), and -SO3H (sulfonic acid) into the nucleophilic sites of the emodin skeleton, the energy barrier for Michael addition reactions is significantly higher than that of ordinary anthraquinone molecules, exhibiting excellent thermodynamic stability. Therefore, the excellent chemical stability described in this invention is attributed to the intrinsic characteristics of the specific skeletal structure of emodin and the steric hindrance effect of its substituents. In this invention, as long as the core characteristics of the emodin skeleton are maintained, the solubility and redox potential of the material can be flexibly controlled through directional functional group modification while ensuring cycle stability. This provides a solid theoretical basis for constructing a family of high-performance, customizable flow battery active materials.

[0050] This invention utilizes a negative electrode active material with an emodin skeleton, taking advantage of specific substituent sites (methyl and hydroxyl groups) naturally present in the molecular structure of the emodin skeleton to effectively block key side reactions (such as Michael addition) that lead to failure from the intrinsic molecular structure. This significantly improves the cycle life and capacity retention of the battery without the need for complex artificial synthesis modifications. At the same time, the negative electrode active material of this invention has the advantages of being widely available and renewable, achieving low-cost, highly safe, and environmentally friendly long-term energy storage.

[0051] In this invention, by using a negative electrode active material with an emodin framework, an aqueous organic flow battery achieves breakthrough cycle stability. The negative electrode active material of this invention exhibits excellent anti-capacity properties, solving the problem of rapid capacity decline caused by Michael addition of traditional quinone molecules.

[0052] In some specific implementations, the supporting electrolyte in the negative electrode electrolyte includes an alkaline substance. This invention employs an aqueous alkaline electrolyte system. The negative electrode active material with an emodin framework is itself non-toxic, non-flammable, and readily biodegradable, completely avoiding the safety hazards of bromine vapor volatilization, strong corrosiveness, and flammability in bromine-based flow batteries, while also avoiding the risk of heavy metal pollution. Specifically, the alkaline substance includes KOH or NaOH.

[0053] In some specific embodiments, the concentration of the negative electrode active material in the negative electrode electrolyte is 0.005~0.2 mol / L, preferably 0.005~0.1 mol / L, for example: 0.01 mol / L, 0.03 mol / L, 0.05 mol / L, 0.08 mol / L, 0.1 mol / L, 0.13 mol / L, 0.15 mol / L, 0.18 mol / L, etc.; the concentration of the supporting electrolyte is 0.5~1.5 mol / L, preferably 0.7~1.2 mol / L; for example: 0.6 mol / L, 0.7 mol / L, 0.8 mol / L, 0.9 mol / L, 1 mol / L, 1.1 mol / L, 1.2 mol / L, 1.3 mol / L, 1.4 mol / L, etc.

[0054] The inventors of this invention have discovered that when the concentration of the negative electrode active material is 0.005~0.2 mol / L and the concentration of the supporting electrolyte is 0.5~1.5 mol / L, the capacity decay rate is low after multiple cycles, and the cycle stability is high. In particular, when the concentration of the negative electrode active material is low, it can far exceed that of traditional quinone materials.

[0055] Specifically, in this invention, the solvent is water.

[0056] A first aspect of the present invention provides a method for preparing a negative electrode electrolyte according to the present invention, which includes the step of mixing a negative electrode active material, a supporting electrolyte and a solvent.

[0057] Specifically, the supporting electrolyte can be dissolved in a solvent to obtain a supporting electrolyte solution, and then the negative electrode active material can be dissolved in the supporting electrolyte solution to obtain a negative electrode electrolyte.

[0058] <Second aspect>

[0059] A second aspect of the present invention provides an aqueous flow battery comprising a positive electrode, a negative electrode, and a separator, wherein the negative electrode comprises a negative electrode electrolyte according to the first aspect.

[0060] In some specific embodiments, the positive electrode includes a positive electrode electrolyte, which comprises a positive electrode active material, a supporting electrolyte, and a solvent. The supporting electrolyte in the positive electrode electrolyte may be the same as or different from the supporting electrolyte in the negative electrode electrolyte. Specifically, the supporting electrolyte in the positive electrode electrolyte includes an alkaline substance. Specifically, the alkaline substance includes KOH or NaOH.

[0061] In some specific embodiments, the present invention does not impose particular limitations on the positive electrode active material, which can be a commonly used positive electrode active material in the art. Specifically, the positive electrode active material includes one or a combination of two or more of soluble ferrocyanate, 2,5-dihydroxybenzenesulfonic acid, and 1,4-dihydroxybenzenesulfonic acid. Preferably, the soluble ferrocyanate includes one or two of potassium ferrocyanide and sodium ferrocyanide; the 1,4-dihydroxybenzenesulfonic acid includes potassium 1,4-dihydroxybenzenesulfonate or sodium 1,4-dihydroxybenzenesulfonate.

[0062] Example

[0063] The embodiments of the present invention will be described in detail below with reference to examples. However, those skilled in the art will understand that the following examples are for illustrative purposes only and should not be considered as limiting the scope of the invention. Unless otherwise specified in the examples, conventional conditions or conditions recommended by the manufacturer are followed. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0064] In this embodiment, the YTH-1 model flow battery is specifically manufactured by Wuhan Zhisheng New Energy Co., Ltd., and its structure includes a bolt-type flow battery test fixture LSB-1, a peristaltic pump, pipelines, a storage tank, a magnetic stirrer, an integrated structure, and a Neware charge-discharge test system.

[0065] The LSB-1 consists of the following components from the outside in: end plate, insulating gasket, galvanized copper plate, rubber sealing ring, graphite plate, sealing sheet, graphite felt electrode, and proton exchange membrane.

[0066] The graphite plate is grooved to form an S-shaped flow channel. The graphite felt electrode is 3 cm × 3 cm × 4.35 cm (H435, carbon content >99%, bulk density 0.08-0.11 g / cm³). 3 Specific surface area 2.3~4 m 2 / g, porosity 90-95%, sheet resistivity <0.1 Ω·cm 2 The membrane material is KVFM212.

[0067] Example 1

[0068] Preparation of negative electrode electrolyte: Emodin, a naturally derived substance, was selected as the negative electrode active material. An appropriate amount of emodin was dissolved in a 1 mol / L KOH alkaline aqueous solution to prepare a negative electrode electrolyte with an emodin concentration of 0.01 mol / L. 30 mL of this negative electrode electrolyte was placed in the negative electrode storage tank.

[0069] Preparation of the positive electrode electrolyte: Potassium ferrocyanide (K4Fe(CN)6) was selected as the positive electrode active material. An appropriate amount of potassium ferrocyanide was dissolved in a 1 mol / L KOH alkaline aqueous solution to prepare a positive electrode electrolyte with a potassium ferrocyanide concentration of 0.02 mol / L. 30 mL of this positive electrode electrolyte was placed in the positive electrode storage tank.

[0070] Flow battery system: The YTH-1 model flow battery testing equipment was used to form a flow battery system.

[0071] Example 2

[0072] The negative electrode 0.01 mol / L emodin in Example 1 was replaced with 0.1 mol / L emodin, and the positive electrode active material was selected as 0.2 mol / L potassium ferrocyanide, which matched the emodin. The amount of other raw materials and the steps were exactly the same as in Example 1.

[0073] Example 3

[0074] The negative electrode 0.01 mol / L emodin in Example 1 was replaced with 0.05 mol / L emodin, and the positive electrode active material was selected as 0.1 mol / L potassium ferrocyanide, which matched the emodin. The amount of other raw materials and the steps were exactly the same as in Example 1.

[0075] Example 4

[0076] The negative electrode 0.01 mol / L emodin in Example 1 was replaced with 0.1 mol / L emodin, and the positive electrode active material was replaced with 0.1 mol / L 2,5-dihydroxybenzenesulfonic acid (HQS cas 88-46-0). The remaining raw material amounts and steps were exactly the same as in Example 1.

[0077] Comparative Example

[0078] The negative electrode active materials of Comparative Examples 1-13 all require relatively complex preparation methods to be prepared, and it is difficult to obtain their raw materials. Therefore, the relevant preparation methods, operation and testing of Comparative Examples 1-13 are all known data recorded in existing literature.

[0079] Comparative Example 1

[0080] Preparation of the negative electrode electrolyte: 9,10-anthraquinone-2,6-disulfonic acid (2,6-AQDS) was selected as the negative electrode active material and prepared into a negative electrode electrolyte with a concentration of 0.02 mol / L. The electrolyte was then tested in 0.1 mol / L phosphate buffer (pH=7). Preparation of the positive electrode electrolyte: Potassium ferricyanide was selected as the positive electrode active material and a corresponding positive electrode electrolyte was prepared.

[0081] Flow battery system: The flow battery device used a Maccor 4200 flow battery testing system, employing a Nafion 117 proton exchange membrane, and a constant current charge-discharge method. The cutoff voltage window was set from 0.0 V (discharge cutoff) to 1.0 V (charge cutoff). During the test, the charge-discharge current was set from 0.5 A to 5 A (corresponding to a geometrically effective area of ​​25 cm²). 2 The electrolyte circulation rate is controlled between 500 mL / min and 1000 mL / min.

[0082] Comparative Example 2

[0083] Preparation of the negative electrode electrolyte: 9,10-anthraquinone-2,7-disulfonate (2,7-AQDS) was selected as the negative electrode active material. It was dissolved in a 0.5 mol / L neutral aqueous solution of Na2SO4 to prepare a negative electrode electrolyte with a 2,7-AQDS concentration of 0.2 mol / L.

[0084] Preparation of the positive electrode electrolyte: Potassium 1,4-dihydroxybenzenesulfonate (HQS) was selected as the positive electrode active material. It was dissolved in a 0.5 mol / L Na2SO4 aqueous solution to prepare a positive electrode electrolyte of the appropriate concentration.

[0085] Flow battery system: The flow battery device used was a LAND CT2001A flow battery testing system, employing a Nafion 117 cation exchange membrane. A constant current charge-discharge method was used, with the cutoff voltage window set from 0.4 V (discharge cutoff) to 1.3 V (charge cutoff). The charge-discharge current density was set to 60 mA / cm² during the test. 2 The electrolyte circulation rate is controlled at 60 mL / min.

[0086] Comparative Example 3

[0087] Preparation of negative electrode electrolyte: Use divalent / trivalent vanadium ions (V... 2+ / V 3+ Vanadium-containing active material is used as the paired negative electrode active material. An appropriate amount of vanadium-containing active material is dissolved in a 1 mol / L strongly acidic aqueous solution of H2SO4 to prepare a negative electrode electrolyte with a total vanadium concentration of 1.0 mol / L.

[0088] Preparation of the positive electrode electrolyte: A synthetically produced naphthalene derivative precursor (TAND) was selected as the positive electrode active material. An appropriate amount of TAND was dissolved in a 1 mol / L strongly acidic aqueous solution of H2SO4 to prepare a positive electrode electrolyte with a concentration of 0.1 mol / L.

[0089] Flow battery system: The flow battery device uses LAND flow battery testing equipment, employs Nafion series ion exchange membranes, and uses a constant current charge-discharge method. The cutoff voltage window is set from 0.1 V (discharge cutoff) to 1.4 V (charge cutoff). During the test, the charge-discharge current density is set to 40 mA / cm². 2 The electrolyte circulation rate is controlled at 30 mL / min.

[0090] Comparative Example 4

[0091] Preparation of the negative electrode electrolyte: Lawsone (2-hydroxy-1,4-naphthoquinone), a derivative of a natural plant of the same genus, was selected as the negative electrode active material. It was dissolved in a 1 mol / L NaCl aqueous solution containing a trace amount of alkali (0.025 mol / L KOH) to prepare a negative electrode electrolyte with a concentration of 0.1 M.

[0092] Preparation of the positive electrode electrolyte: A synthetically produced organic nitrogen oxide radical (4-HO-TEMPO) was selected as the positive electrode active material. It was dissolved in the same 1 mol / L NaCl supporting electrolyte to prepare a positive electrode electrolyte of the appropriate concentration.

[0093] Flow battery system: The flow battery device used a Solartron 1470E flow battery testing system, employing a Nafion 117 proton exchange membrane, and a constant current charge-discharge method. The cutoff voltage window was set from 0.1 V (discharge cutoff) to 1.6 V (charge cutoff). During the test, the charge-discharge current density was set to 5 mA / cm². 2 The electrolyte circulation rate is controlled at 20 mL / min.

[0094] Comparative Example 5

[0095] Preparation of negative electrode electrolyte: Rhein, an anthraquinone compound extracted from natural plants, was selected as the negative electrode active material. It was dissolved in a 2 mol / L KOH aqueous solution to prepare a negative electrode electrolyte with a rhein concentration of 0.1 mol / L (10 mL was prepared for later use).

[0096] Preparation of positive electrode electrolyte: Potassium ferrocyanide was selected as the positive electrode active material and a positive electrode electrolyte with a concentration of 0.1 mol / L was prepared (25 mL was prepared for later use).

[0097] Flow battery system: A YTH-1 flow battery testing device was used, employing a Nafion 1135 cation exchange membrane. A constant current charge-discharge method was employed, with the cutoff voltage window set from 0.3 V (discharge cutoff) to 1.4 V (charge cutoff). The charge-discharge current density was set to 40 mA / cm² during the test. 2 The electrolyte circulation rate is controlled at 60 mL / min.

[0098] Comparative Example 6

[0099] Add 0.5 mol / L NH4Cl to the negative electrode electrolyte of Comparative Example 5 and adjust the pH to 12.6. The remaining steps are exactly the same as those of Comparative Example 5.

[0100] Comparative Example 7

[0101] Preparation of the negative electrode electrolyte: 9,10-anthraquinone-2,6-dipropionic acid (AQDP), a synthetically produced substance with complex modifications, was selected as the negative electrode active material. An appropriate amount of AQDP was dissolved in an aqueous solution and the pH was adjusted to 12 to prepare a negative electrode electrolyte with a concentration of 1.0 mol / L.

[0102] Preparation of the positive electrode electrolyte: Potassium ferrocyanide and potassium ferricyanide were selected as the positive electrode active materials. A positive electrode electrolyte (pH = 12) containing 0.5 mol / L potassium ferrocyanide and 0.1 mol / L potassium ferricyanide was prepared.

[0103] Flow battery system: The flow battery device used a Neware model flow battery testing system, employing a Nafion 212 proton exchange membrane, and a constant current charge-discharge method. The cutoff voltage window was set from 0.2 V (discharge cutoff) to 1.1 V (charge cutoff). During the test, the charge-discharge current density was set to 20 mA / cm². 2 The electrolyte circulation rate is controlled at 60 mL / min.

[0104] Comparative Example 8

[0105] Preparation of negative electrode electrolyte: Alizarin-3-methyliminodiacetic acid (AMA), a synthetically modified substance, was selected as the negative electrode active material. An appropriate amount of AMA was dissolved in an aqueous solution, and 0.2 mol / L potassium hydroxide (KOH) was added as a supporting electrolyte to prepare a negative electrode electrolyte with a concentration of 0.4 mol / L (8 mL).

[0106] Preparation of the positive electrode electrolyte: Potassium ferrocyanide was selected as the positive electrode active material. It was prepared into a positive electrode electrolyte containing 0.4 mol / L potassium ferrocyanide (containing 0.2 mol / L KOH supporting electrolyte, 24 mL).

[0107] Flow battery system: The flow battery device used a LAND CT2001A flow battery testing system, employing a Nafion 211 proton exchange membrane, and a constant current charge-discharge method. The cutoff voltage window was set from 0.2 V (discharge cutoff) to 1.65 V (charge cutoff). During the test, the charge-discharge current density was set to 100 mA / cm². 2 The electrolyte circulation rate is controlled at 100 mL / min.

[0108] Comparative Example 9

[0109] Preparation of negative electrode electrolyte: Benzohydroxyphenazine-7 / 8-carboxylic acid (BHPC), a synthetically produced fused-ring phenazine derivative, was selected as the negative electrode active material. An appropriate amount of BHPC was dissolved in a 1.0 mol / L potassium hydroxide (KOH) aqueous solution to prepare a 0.5 mol / L negative electrode electrolyte (10 mL).

[0110] Preparation of the positive electrode electrolyte: Potassium ferrocyanide was selected as the positive electrode active material. It was prepared into a positive electrode electrolyte containing excess potassium ferrocyanide (15 mL of 1.0 mol / L KOH aqueous solution as the supporting electrolyte).

[0111] Flow battery system: The flow battery device used was a LAND CT2001A flow battery testing system, employing a Nafion 117 proton exchange membrane and a constant current charge-discharge method. The cutoff voltage window was set from 0.4 V (discharge cutoff) to 1.4 V (charge cutoff). The charge-discharge current density was set to 20 mA / cm² during the test. 2 The electrolyte circulation flow rate is controlled at 30 mL / min.

[0112] Comparative Example 10

[0113] Preparation of negative electrode electrolyte: 2,3-dihydroxyanthraquinone (2,3-DHAQ), a synthetically produced substance, was selected as the negative electrode active material. An appropriate amount of 2,3-DHAQ was dissolved in a 1.8 mol / L potassium hydroxide (KOH) aqueous solution to prepare a 0.2 mol / L negative electrode electrolyte (40 mL).

[0114] Preparation of the positive electrode electrolyte: Potassium ferrocyanide was selected as the positive electrode active material. It was prepared into a positive electrode electrolyte containing 0.5 mol / L potassium ferrocyanide (with 0.2 mol / L sodium hydroxide aqueous solution as the supporting electrolyte, 44 mL).

[0115] Flow battery system: The flow battery device used a BioLogic BCS-815 flow battery testing system, employing a Nafion 211 proton exchange membrane, and a constant current charge-discharge method. The cutoff voltage window was set from 0.3 V (discharge cutoff) to 1.2 V (charge cutoff). During the test, the charge-discharge current density was set to 20 mA / cm². 2 The electrolyte circulation rate is controlled at 60 mL / min.

[0116] Comparative Example 11

[0117] Preparation of the negative electrode electrolyte: 1,8-bis(2-(2-(2-hydroxyethoxy)ethoxy)ethoxy)anthracene-9,10-dione (AQ-1,8-3E-OH), an anthraquinone derivative with a polyethylene glycol (PEG) side chain introduced through artificial synthesis, was selected as the negative electrode active material. It was dissolved in a neutral aqueous solution (pH = 7) containing 0.5 mol / L KCl to prepare a negative electrode electrolyte with a concentration as high as 1.5 mol / L.

[0118] Preparation of the positive electrode electrolyte: Potassium ferrocyanide and potassium ferricyanide were selected as the positive electrode active materials. To match the extremely high negative electrode capacity, a mixed salt strategy was adopted to prepare a positive electrode electrolyte (pH = 12) containing 0.5 mol / L potassium ferrocyanide and 0.1 mol / L potassium ferricyanide.

[0119] Flow battery system: The flow battery device used a Gamry Reference 3000 flow battery testing system, employing a Fumasep E-620 (K) anion exchange membrane, and a constant current charge-discharge method. The cutoff voltage window was set from 0.2 V (discharge cutoff) to 1.15 V (charge cutoff). The charge-discharge current density was set to 20 mA / cm² during the test. 2 The electrolyte circulation rate is controlled at 60 mL / min.

[0120] Comparative Example 12

[0121] Preparation of negative electrode electrolyte: 4-Carboxy-7-sulfonic acid fluorenone (4C7SFL), a synthetically modified fluorenone derivative, was selected as the negative electrode active material. An appropriate amount of 4C7SFL was dissolved in a 1 mol / L sodium hydroxide (NaOH) aqueous solution to prepare a negative electrode electrolyte with a concentration of 1.0 mol / L.

[0122] Preparation of the positive electrode electrolyte: Potassium ferrocyanide and potassium ferricyanide were selected as the positive electrode active materials. A positive electrode electrolyte (pH = 12) containing 0.5 mol / L potassium ferrocyanide and 0.1 mol / L potassium ferricyanide was prepared.

[0123] Flow battery system: The flow battery device uses an Arbin model flow battery testing device and employs a Nafion ion exchange membrane (specifically, Nafion 115 or Nafion 212 membrane). A constant current charge / discharge method is used, with the cutoff voltage window set from 0.5 V (discharge cutoff) to 1.3 V (charge cutoff). During the test, the charge / discharge current density is set to 20 mA / cm². 2 The electrolyte circulation rate is controlled at 40 mL / min.

[0124] Comparative Example 13

[0125] Preparation of negative electrode electrolyte: 1,8-dihydroxyanthraquinone (1,8-DHAQ), a naturally modified anthraquinone derivative, was selected as the negative electrode active material. An appropriate amount of 1,8-DHAQ was dissolved in a 1.0 mol / L potassium hydroxide (KOH) aqueous solution to prepare a negative electrode electrolyte with a concentration of 0.1 mol / L.

[0126] Preparation of the positive electrode electrolyte: Potassium ferrocyanide and potassium ferricyanide were selected as the positive electrode active materials. They were dissolved in a 1.0 mol / L potassium hydroxide (KOH) aqueous solution to prepare a positive electrode electrolyte containing 0.2 mol / L potassium ferrocyanide and 0.01 mol / L potassium ferricyanide.

[0127] Flow battery system: The flow battery device used a LAND CT2001A flow battery testing system, employing a Nafion 212 proton exchange membrane, and a constant current charge-discharge method. The cutoff voltage window was set from 0.2 V (discharge cutoff) to 1.4 V (charge cutoff). During the test, the charge-discharge current density was set to 20 mA / cm². 2 The electrolyte circulation flow rate is controlled at 16 mL / min.

[0128] Effect test

[0129] 1. Battery operation and testing:

[0130] A constant voltage charging method was used, with the cutoff voltage window set from 0.5 V (discharge cutoff) to 1.6 V (charge cutoff). During the test, the cutoff current was set to 50 mA, and the electrolyte circulation flow rate was controlled at 60 mL / min to ensure sufficient mass transfer and reaction uniformity. The test results for Examples 1-4 are shown in Table 1 and... Figure 1 As shown in the table, the relevant data for Comparative Examples 1-13 are all known data recorded in the prior art.

[0131] Table 1

[0132]

[0133] As can be seen from Table 1, the capacity decay rate of the liquid battery systems in Examples 1 and 3 after more than 1,000 cycles is only 0.002% and 0.003% per cycle, respectively, which is far superior to other traditional quinone materials in Comparative Examples 1-13.

[0134] The liquid battery systems of Examples 2 and 3 exhibited capacity decay rates of 0.011% and 0.022% per cycle, respectively, after more than 100 cycles, and still demonstrated excellent cycle stability.

[0135] Compared with rhein in Comparative Examples 5 and 6, the emodin of the present invention improves cycle stability by orders of magnitude. It is evident that the negative electrode active material of the present invention effectively blocks the Michael addition side reaction through the synergistic effect of specific sites of methyl and hydroxyl groups, achieving an order-of-magnitude improvement in stability (attenuation rate as low as 0.002% / cycle).

[0136] in addition, Figure 1 The battery cycle performance of the flow battery systems in Examples 1-4 of this invention is shown. Figure 1 It can be seen that when using emodin as the negative electrode active material, the flow battery system of Example 1 exhibits a capacity decay rate of 0.01% per cycle after more than 100 cycles (over 170 hours of operation). Furthermore, the actual capacity is approximately 460 C, reaching 80% of the theoretical capacity (theoretical capacity is 579 C), demonstrating excellent battery cycle performance. The flow battery system of Example 2 exhibits a capacity decay rate of 0.002% per cycle after 1000 cycles (over 170 hours). Furthermore, the actual capacity is approximately 46.8 C, exceeding 80% of the theoretical capacity (theoretical capacity is 57.9 C).

[0137] Furthermore, the applicant provides a performance comparison of flow batteries for Comparative Example 5, Comparative Example 13, and Example 2, as shown in Table 2 below.

[0138] Table 2

[0139]

[0140] As can be seen from Table 2, the overall performance of the flow battery system using the present invention is superior to that of Comparative Example 5 and Comparative Example 13.

[0141] 2. Liquid phase testing

[0142] Liquid phase testing was performed by taking 100 μL of the negative electrode electrolyte from Example 1 from the outlet after the first full charge (before cycling) and the last full charge (after cycling) during the cycle, and diluting it with 900 μL of 0.1wt% formic acid solution. The results are as follows. Figure 2 As shown.

[0143] The liquid chromatography system used was a Shimadzu LC-20A modular HPLC system (Shimadzu Corporation, Kyoto, Japan). The liquid chromatography column used was a Shim-pack VP-ODS column (4.6 × 150 mm, 5 μm, Shimadzu, Japan). The flow rate was 0.4 ml / min. The elution conditions were as follows (solvent A was a 0.1 wt% aqueous solution of formic acid; solvent B was an acetonitrile solution containing 0.1 wt% formic acid): 95% solvent A was held for 2 min, then the proportion of solvent B in solvent A was gradually increased from 5% to 60% over 13 min, then increased to 95% (solvent B) over 5 min, then decreased to 5% (solvent B) over 0.1 min, and finally held at 95% solvent A for 4.9 min.

[0144] Depend on Figure 2 It can be seen that the peak position and intensity of the negative electrode electrolyte are basically the same before and after cycling, which also indicates that no side reactions occurred before and after cycling, and the effective active substance is still emodin, further demonstrating the strong cycling stability of the present invention.

[0145] 3. Nucleophilic addition reaction energy

[0146] Nucleophilic addition reaction sites were predicted by calculating the condensed dual descriptor (CDD) of the quinone structure. The addition energies of key side reaction pathways were calculated using the Born-Haber cycle. Specifically, the quinone structure underwent geometric optimization and vibrational analysis using Gaussian 16 at B3LYP / 6-31G* accuracy. CDD calculations were performed using the output wavefunction information; the site with the highest CDD value corresponds to the most readily nucleophilic addition site. The byproduct (phenolic structure) after addition was also subjected to geometric optimization and vibrational analysis at B3LYP / 6-31G* accuracy. Single-point energies were calculated using the SMD continuous medium solvent model at M052X / 6-31G* accuracy. A complete thermodynamic cycle was constructed using the Born-Haber cycle to calculate the reaction energies. The results are shown in Table 3.

[0147] Table 3

[0148]

[0149] As can be seen from Table 3, the energy barrier for the Michael addition reaction of other negative electrode active materials of the present invention, such as the derivatives of emodin, is significantly higher than that of ordinary anthraquinone molecules, revealing their excellent thermodynamic stability.

[0150] It should be noted that although the technical solution of the present invention has been described with specific examples, those skilled in the art will understand that the present invention should not be limited thereto.

[0151] The various embodiments of the present invention have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is chosen to best explain the principles, practical application, or technical improvements to the embodiments in the market, or to enable others skilled in the art to understand the embodiments disclosed herein.

Claims

1. A negative electrode electrolyte, characterized in that, The negative electrode electrolyte includes a negative electrode active material, a supporting electrolyte, and a solvent; wherein... The negative electrode active material has the structure shown in formula (1): （1） Where R represents H, -NH2, -OH, -CHO, -COOH, -PO3H2 or -SO3H.

2. The negative electrode electrolyte according to claim 1, characterized in that, The supporting electrolyte in the negative electrode electrolyte includes an alkaline substance.

3. The negative electrode electrolyte according to claim 2, characterized in that, The alkaline substance includes KOH or NaOH.

4. The negative electrode electrolyte according to any one of claims 1-3, characterized in that, In the negative electrode electrolyte, the concentration of the negative electrode active material is 0.005~0.2 mol / L, and the concentration of the supporting electrolyte is 0.5~1.5 mol / L.

5. The negative electrode electrolyte according to any one of claims 1-4, characterized in that, The solvent is water.

6. A method for preparing a negative electrode electrolyte according to any one of claims 1-5, characterized in that, This includes the step of mixing the negative electrode active material, the supporting electrolyte, and the solvent.

7. An aqueous organic flow battery, characterized in that, It includes a positive electrode, a negative electrode, and a separator, wherein the negative electrode includes the negative electrode electrolyte according to any one of claims 1-5.

8. The aqueous organic flow battery according to claim 7, characterized in that, The positive electrode includes a positive electrolyte, which includes a positive active material, a supporting electrolyte, and a solvent.

9. The aqueous organic flow battery according to claim 8, characterized in that, The positive electrode active material includes one or more of soluble ferrocyanate, 2,5-dihydroxybenzenesulfonic acid, and 1,4-dihydroxybenzenesulfonic acid.

10. The aqueous organic flow battery according to claim 9, characterized in that, The soluble ferrocyanate includes potassium ferrocyanide or sodium ferrocyanide. The 1,4-dihydroxybenzenesulfonate includes potassium 1,4-dihydroxybenzenesulfonate or sodium 1,4-dihydroxybenzenesulfonate.

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