Negative electrode electrolyte of zinc-iron flow battery and zinc-iron flow battery

Abstract

The invention relates to the technical field of battery energy storage, in particular to a negative electrode electrolyte of a zinc-iron flow battery and the zinc-iron flow battery. The invention provides a negative electrode electrolyte of a zinc-iron flow battery. The negative electrode electrolyte is prepared from the following raw materials: a zinc-based redox active substance, a supporting electrolyte, a quinone molecular additive and a solvent, wherein the redox potential of the quinone molecular additive is higher than that of the zinc negative electrode under the same condition. According to the negative electrode electrolyte provided by the invention, dead zinc which loses electric contact can be converted into zinc with electrochemical activity again by utilizing the mediation effect of the anthraquinone derivative additive, namely the reutilization of the dead zinc in the zinc-based flow battery and the recovery of the lost capacity are realized through the redox targeting reaction between the anthraquinone derivative and the dead zinc; therefore, the cycle life of the zinc-iron flow battery is obviously prolonged.

Description

Technical Field

[0001] The present invention relates to the technical field of battery energy storage, and in particular to a negative electrode electrolyte of a zinc-iron liquid flow battery and a zinc-iron liquid flow battery. Background Art

[0002] Liquid flow battery is a new type of battery. It is a high-performance battery that uses positive and negative electrolytes to circulate separately. It realizes the mutual conversion of electrical energy and chemical energy through reversible redox reactions of active substances in positive and negative electrolyte solutions. With the growing global demand for renewable energy and environmental protection technologies, the application prospects of zinc-based liquid flow batteries in the field of energy storage are very broad. Zinc-based redox liquid flow battery is a new type of battery technology that uses zinc and its compounds to store and release energy through redox reactions. The core of this battery technology lies in its unique liquid flow design, which allows the electrolyte to be stored and circulated independently of the battery reaction area, thereby realizing the flexible adjustment of the battery energy storage capacity and power. The working principle of zinc-based liquid flow battery is relatively simple and efficient. During the charging process, zinc deposition occurs at the negative electrode, and at the same time, the redox active medium (such as bromine, iodine or iron ions) of the positive electrode is oxidized at the positive electrode. Reversibly, during discharge, zinc metal dissolves in the negative electrode electrolyte and releases energy, while the positive electrode is reduced to form current output. This process not only achieves efficient energy conversion, but also ensures the long-term stability and safety of the battery.

[0003] Zinc-based flow batteries have many technical advantages. First, zinc is an abundant, cheap and environmentally friendly metal, which gives zinc-based flow batteries certain cost advantages. Second, zinc-based flow batteries have a high energy density and are suitable for various occasions that require long-term stable power supply. In addition, zinc-based flow batteries also have the characteristics of high safety, long life and easy maintenance, making them one of the preferred technologies in the field of large-scale energy storage.

[0004] However, zinc-based flow batteries also face some technical challenges. For example, the reversibility of the deposition and dissolution reaction of the zinc negative electrode, the hydrogen evolution problem, and the hydrolysis problem, etc., these problems may affect the cycle stability and efficiency of the battery. In addition, the formation of zinc dendrites is also one of the key problems that zinc-based flow batteries need to solve, which may cause internal short circuits and capacity decay in the battery. Specifically, during the redox process of zinc charging, Zn metal will be deposited, and the deposition sites are limited. Therefore, after a certain amount of deposition, it will not be able to continue to react, affecting the cycle life of the zinc-based flow battery. Summary of the invention

[0005] In view of this, the present invention provides a negative electrode electrolyte for a zinc-iron flow battery and a zinc-iron flow battery. The negative electrode electrolyte provided by the present invention can convert "dead zinc" that has lost electrical contact into electrochemically active zinc, thereby realizing capacity recovery and significantly improving the cycle life of the zinc-based flow battery.

[0006] The present invention provides a negative electrode electrolyte for a zinc-iron liquid flow battery, the preparation raw materials of which include: a zinc-based redox active substance, a supporting electrolyte, a quinone molecular additive and a solvent;

[0007] Among them, the redox potential of the quinone molecular additive is higher than the redox potential of the zinc negative electrode under the same conditions.

[0008] Preferably, the quinone molecular additive is an anthraquinone derivative;

[0009] The anthraquinone derivative is at least one of 1,2-dihydroxyanthraquinone, 1,4-dihydroxyanthraquinone, 1,5-dihydroxyanthraquinone, 1,8-dihydroxyanthraquinone, 2,6-dihydroxyanthraquinone, anthraquinone-2,7-disulfonic acid disodium salt, 4,4'-([9,10-anthraquinone-2,6-diyl]dioxy)dibutyrate, (9,10-dioxy-9,10-dihydroanthracene-2,6-diyl)bis(oxy))bis(propane-3,1-diyl))bis(phosphonic acid), and 3,3'-(9,10-anthraquinonediyl)bis(3-methylbutyric acid).

[0010] Preferably, the zinc-based redox active substance is at least one of zinc oxide, zinc chloride, zinc iodide and zinc bromide.

[0011] Preferably, the supporting electrolyte is at least one of a soluble metal hydroxide and a metal halide.

[0012] Preferably, the soluble metal hydroxide is at least one of sodium hydroxide, potassium hydroxide and lithium hydroxide;

[0013] The metal halide is at least one of sodium chloride, potassium chloride and lithium chloride.

[0014] Preferably, the solvent is water and / or an organic solvent.

[0015] Preferably, the concentration of the quinone molecular additive in the solvent is 0.001 to 0.1 mol / L;

[0016] The concentration of the zinc-based redox-active substance in the solvent is ≤5 mol / L;

[0017] The concentration of the supporting electrolyte in the solvent is ≤5 mol / L.

[0018] The present invention also provides a zinc-iron liquid flow battery, comprising:

[0019] Battery stack unit;

[0020] A cathode storage tank, containing cathode electrolyte;

[0021] A cathode storage tank, containing cathode electrolyte;

[0022] Wherein, the negative electrode electrolyte is the negative electrode electrolyte described in the above technical solution.

[0023] Preferably, the active ingredient of the positive electrode electrolyte is at least one of an iron-based complex, a ferrous-based complex, an iron salt and a ferrous salt.

[0024] Preferably, the diaphragm in the stack unit is a perfluorosulfonic acid ion membrane, a sulfonated polyetheretherketone membrane or an Asahi Glass anion membrane.

[0025] The negative electrode electrolyte provided by the present invention utilizes the mediation effect of anthraquinone derivative additives to reconvert "dead zinc" that has lost electrical contact into electrochemically active zinc, that is, through the targeted redox reaction between anthraquinone derivatives and dead zinc, the dead zinc in the zinc-based flow battery is reused and the lost capacity is restored, thereby significantly extending the cycle life of the zinc-iron flow battery. Moreover, the anthraquinone derivatives introduced by the present invention do not introduce harmful substances and are environmentally friendly. The present invention innovatively solves the problem of limited surface capacity and current density caused by dead zinc in zinc-based flow batteries, while significantly improving the cycle stability and energy efficiency of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0027] Figure 1 This is a diagram showing the effect of cyclic voltammetry testing of anthraquinone derivatives in Example 1-3;

[0028] Figure 2 This is a test result of the cycle performance of zinc-based symmetric flow battery;

[0029] Figure 3 This is the effect diagram of the cycle performance test of zinc-iron flow battery;

[0030] Figure 4 This is the test effect diagram of the cumulative surface capacity of the zinc-iron flow battery and the capacity contribution of dead zinc;

[0031] Figure 5This is a test result of the cycle performance of a high-area capacity zinc-iron flow battery;

[0032] Figure 6 This is the charge and discharge curve test effect diagram of the zinc-iron flow battery. DETAILED DESCRIPTION

[0033] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The terms used herein in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application.

[0034] In this article, the technical features described in an open manner include closed technical solutions composed of the listed features, and also include open technical solutions containing the listed features.

[0035] As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items.

[0036] Herein, when it comes to numerical ranges, unless otherwise specified, the numerical ranges are deemed to be continuous and include the minimum and maximum values ​​of the range, as well as every value between such minimum and maximum values. Further, when a range refers to an integer, every integer between the minimum and maximum values ​​of the range is included. In addition, when multiple ranges are provided to describe features or characteristics, the ranges can be merged. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges included therein.

[0037] In this article, when referring to the unit of a data range, if there is a unit only after the right endpoint, it means that the units of the left and right endpoints are the same. For example, 0.001~0.1mol / L means that the units of the left endpoint "0.001" and the right endpoint "0.1" are both mol / L.

[0038] The present invention provides a negative electrode electrolyte for a zinc-iron liquid flow battery, the preparation raw materials of which include: a zinc-based redox active substance, a supporting electrolyte, a quinone molecular additive and a solvent;

[0039] Among them, the redox potential of the quinone molecular additive is higher than the redox potential of the zinc negative electrode under the same conditions.

[0040] The present invention adds specific quinone molecules with a higher equilibrium reaction potential than the zinc negative electrode as redox mediators into the negative electrode electrolyte, and utilizes their spontaneous targeted reaction with zinc metal to convert "dead zinc" that has lost electrical contact into electrochemically active zinc, thereby achieving capacity recovery and greatly improving the cycle life of the zinc-based liquid flow battery.

[0041] In the present invention, the zinc-based redox active substance is preferably at least one of zinc oxide, zinc chloride, zinc iodide and zinc bromide. In the present invention, the concentration of the zinc-based redox active substance in the solvent is preferably ≤5 mol / L, specifically 0.1 mol / L, 0.3 mol / L, 0.5 mol / L, 1.0 mol / L, 1.5 mol / L, 2.0 mol / L, 2.5 mol / L, 3.0 mol / L, 3.5 mol / L, 4.0 mol / L, 4.5 mol / L, 5.0 mol / L.

[0042] In the present invention, the supporting electrolyte is preferably at least one of a soluble metal hydroxide and a metal halide. Among them, the soluble metal hydroxide is preferably at least one of NaOH, KOH and LiOH. The metal halide is preferably at least one of NaCl, KCl and LiCl. In the present invention, the concentration of the supporting electrolyte in the solvent is preferably ≤5mol / L, specifically 0.1mol / L, 0.5mol / L, 1.0mol / L, 1.5mol / L, 2.0mol / L, 2.5mol / L, 3.0mol / L, 3.5mol / L, 3.8mol / L, 4.0mol / L, 4.5mol / L, 5.0mol / L.

[0043] In the present invention, the redox potential of the quinone molecular additive is higher than the redox potential of the zinc negative electrode under the same conditions, and is preferably an anthraquinone derivative, more preferably 1,2-dihydroxyanthraquinone (i.e., 1,2-DHAQ), 1,4-dihydroxyanthraquinone (i.e., 1,4-DHAQ), 1,5-dihydroxyanthraquinone (i.e., 1,5-DHAQ), 1,8-dihydroxyanthraquinone (i.e., 1,8-DHAQ), 2,6-dihydroxyanthraquinone (i.e., 2,6-DHAQ), anthraquinone-2,7-disulfonic acid disodium salt, 4,4'-([9,10-anthraquinone-2,6-diyl]dioxy)dibutyrate, (9,10-dioxy-9,10-dihydroanthracene-2,6-diyl)bis(oxy))bis(propane-3,1-diyl))bis(phosphonic acid), and 3,3'-(9,10-anthraquinonediyl)bis(3-methylbutyric acid). The present invention introduces the above-mentioned anthraquinone derivative additive into the negative electrode electrolyte, which is oxidized in the electrochemical reaction and catalytically promotes the zinc that has lost electrical contact (i.e., "dead zinc") to be converted back into electrochemically active zinc-based redox substances, thereby restoring and enhancing the capacity of the battery and improving the cycle life of the zinc-based liquid flow battery. In the present invention, during preparation, the amount of the quinone molecular additive is such that the concentration of the quinone molecular additive in the solvent is 0.001 to 0.1 mol / L, specifically 0.001 mol / L, 0.005 mol / L, 0.01 mol / L, 0.015 mol / L, 0.05 mol / L, 0.1 mol / L.

[0044] In the present invention, the solvent is preferably water and / or an organic solvent. Wherein, the organic solvent is preferably at least one of ethylene glycol dimethyl ether (DME), diethylene glycol dimethyl ether (DEG), tetraethylene glycol dimethyl ether (TEG), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), methyl propyl carbonate (MPC) and tetrahydrofuran (THF).

[0045] The present invention also provides a method for preparing the negative electrode electrolyte of the zinc-iron flow battery described in the above technical solution, comprising: mixing a zinc-based redox active substance, a supporting electrolyte, a quinone molecular additive and a solvent to obtain a negative electrode electrolyte. The types and amounts of the zinc-based redox active substance, the supporting electrolyte, the quinone molecular additive and the solvent are consistent with those described in the above technical solution, and will not be described one by one here.

[0046] In the present invention, preferably, the supporting electrolyte is first dissolved in a solvent to form a supporting electrolyte solution, and then a zinc-based redox active substance and a quinone molecular additive are added to obtain a negative electrode electrolyte.

[0047] [About zinc-iron flow battery]:

[0048] The present invention also provides a zinc-iron liquid flow battery, comprising:

[0049] Battery stack unit;

[0050] A cathode storage tank, containing cathode electrolyte;

[0051] A cathode storage tank, containing cathode electrolyte;

[0052] Wherein, the negative electrode electrolyte is the negative electrode electrolyte described in the above technical solution.

[0053] In the present invention, there is no special restriction on the structural composition of the battery stack unit, which can be the conventional structural composition of zinc-based liquid flow battery / zinc-iron liquid flow battery, that is, including: positive electrode, negative electrode and diaphragm. The present invention has no special restrictions on the positive electrode and negative electrode, which can be the conventional positive and negative electrodes of zinc-based liquid flow battery / zinc-iron liquid flow battery, and the present invention does not improve on this. Inside the battery stack, the positive and negative electrolytes are separated by a diaphragm. In the present invention, the diaphragm is preferably a perfluorosulfonic acid ion membrane (Nafion), a sulfonated polyetheretherketone (SPEEK) membrane or Asahi Glass (SELEMION TM ) anion membrane.

[0054] In the present invention, the negative electrode storage tank is filled with negative electrode electrolyte, and the positive electrode storage tank is filled with positive electrode electrolyte, and the electrolyte is transported to the inside of the battery stack through a liquid delivery pump and a pipeline for reaction. In the present invention, the negative electrode electrolyte is the negative electrode electrolyte described in the above technical solution, which will not be described in detail here.

[0055] In the present invention, the active ingredient in the positive electrode electrolyte is at least one of an iron-based complex, a ferrous complex, an iron salt and a ferrous salt. Among them, the iron-based complex is preferably at least one of potassium ferrocyanide, sodium ferrocyanide, sodium di(2,2'pyridine-4,4'dicarboxylic acid) dicyanoferrate, sodium mono(2,2'pyridine-4,4'dicarboxylic acid) tetracyanoferrate and sodium tri(2,2'pyridine-4,4'dicarboxylic acid) ferrate. The ferrous complex is preferably at least one of potassium ferrocyanide, sodium ferrocyanide, sodium di(2,2'pyridine-4,4'dicarboxylic acid) dicyanoferrate, sodium mono(2,2'pyridine-4,4'dicarboxylic acid) tetracyanoferrate and sodium tri(2,2'pyridine-4,4'dicarboxylic acid) ferrate. The iron salt is preferably at least one of ferric chloride, ferric sulfate and ferric chromate. The ferrous salt is preferably at least one of ferrous chloride, ferrous sulfate and ferrous chromate.

[0056] In the present invention, preferably, the positive electrode electrolyte comprises: an active component, a supporting electrolyte and a solvent.

[0057] in:

[0058] The active ingredient is consistent with that described in the above technical solution and will not be described in detail here. The concentration of the active ingredient in the solvent is preferably 0.01 to 0.8 mol / L, specifically 0.01 mol / L, 0.05 mol / L, 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, 0.4 mol / L, 0.5 mol / L, 0.6 mol / L, 0.7 mol / L, 0.8 mol / L.

[0059] The supporting electrolyte is preferably at least one of a soluble metal hydroxide and a metal halide. Among them, the soluble metal hydroxide is preferably at least one of NaOH, KOH and LiOH. The metal halide is preferably at least one of NaCl, KCl and LiCl. In the present invention, the concentration of the supporting electrolyte in the solvent is preferably ≤5 mol / L, specifically 0.1 mol / L, 0.5 mol / L, 1.0 mol / L, 1.5 mol / L, 2.0 mol / L, 2.5 mol / L, 3.0 mol / L, 3.5 mol / L, 3.8 mol / L, 4.0 mol / L, 4.5 mol / L, 5.0 mol / L.

[0060] The solvent is preferably water, more preferably deionized water.

[0061] The present invention has no special restrictions on the preparation method of the positive electrode electrolyte, and the above substances can be mixed and dissolved uniformly.

[0062] The present invention has no special restrictions on the assembly process of the zinc-iron liquid flow battery, and the assembly can be carried out according to the conventional assembly method in the art.

[0063] In the present invention, the cut-off voltage of the zinc-iron flow battery during the charge and discharge process is 0.5 to 2.3 V. During the charge and discharge process, the zinc-based redox active substance in the negative electrode electrolyte is reversibly deposited as zinc metal, and the added quinone molecular additive itself is reduced; specifically, during discharge, the anthraquinone derivative additive added to the negative electrode electrolyte is oxidized on the battery stack, and at the same time, the dead zinc that has lost electrical contact between the battery stack and the electrolyte tank is re-oxidized into electrochemically active zinc-based redox substances, and itself is reduced, and finally the quinone derivative additive added is completely oxidized when the dead zinc is exhausted, that is, the discharge is cut off.

[0064] The negative electrode electrolyte provided by the present invention utilizes the mediation effect of anthraquinone derivative additives to reconvert "dead zinc" that has lost electrical contact into electrochemically active zinc, that is, through the targeted redox reaction between anthraquinone derivatives and dead zinc, the dead zinc in the zinc-based flow battery / zinc-iron flow battery is reused and the lost capacity is restored, thereby significantly extending the cycle life of the zinc-iron flow battery. Moreover, the anthraquinone derivatives introduced by the present invention do not introduce harmful substances and are environmentally friendly. The present invention innovatively solves the problem of limited surface capacity and current density caused by dead zinc in zinc-based flow batteries, while significantly improving the cycle stability and energy efficiency of the battery. This technological breakthrough helps to reduce the operating cost of the battery, improve energy utilization efficiency, reduce the risk of internal short circuit and capacity attenuation of the battery, and improve the reliability and safety of the battery, which is of great significance for the application of flow batteries in long-term energy storage. Moreover, the present invention is simple to operate, low-cost and suitable for large-scale production, and has high application value and potential in the field of flow battery energy storage.

[0065] The present invention has high feasibility in material selection, electrolyte preparation, battery assembly, etc. The anthraquinone derivative redox medium and supporting electrolyte materials used are easy to obtain and relatively low in cost, which is conducive to the promotion and application of the technology.

[0066] In order to further understand the present invention, preferred embodiments of the present invention are described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, rather than limiting the claims of the present invention.

[0067] Example 1

[0068] 1. Raw materials of negative electrode electrolyte:

[0069] Zinc-based redox active substance: zinc oxide, used in an amount of 0.3 mol / L in a solvent;

[0070] Supporting electrolyte: NaOH, with a concentration of 3.8 mol / L in the solvent;

[0071] Anthraquinone derivative: 1,5-DHAQ, the concentration in the solvent is 0.015 mol / L;

[0072] Solvent: deionized water, 30 mL.

[0073] 2. Preparation of negative electrode electrolyte:

[0074] Weigh NaOH and dissolve it in 30 mL of deionized water. After it is completely dissolved, add zinc oxide and stir until it becomes clear. Then add 1,5-DHAQ and stir to dissolve evenly to obtain a negative electrode electrolyte.

[0075] Negative electrolyte composition: 0.015mol / L 1,5-DHAQ+0.3mol / L[Zn(OH) 4 ] 2- +3.8mol / L NaOH.

[0076] Example 2

[0077] 1. Raw materials of negative electrode electrolyte:

[0078] Zinc-based redox active substance: zinc oxide, used in an amount of 0.3 mol / L in a solvent;

[0079] Supporting electrolyte: NaOH, with a concentration of 3.8 mol / L in the solvent;

[0080] Anthraquinone derivative: 1,8-DHAQ, the concentration in the solvent is 0.015 mol / L;

[0081] Solvent: deionized water, 30 mL.

[0082] 2. Preparation of negative electrode electrolyte:

[0083] Weigh NaOH and dissolve it in 30 mL of deionized water. After it is completely dissolved, add zinc oxide and stir until it becomes clear. Then add 1,8-DHAQ and stir to dissolve evenly to obtain a negative electrode electrolyte.

[0084] Negative electrolyte composition: 0.015mol / L 1,8-DHAQ+0.3mol / L[Zn(OH) 4 ] 2- +3.8mol / L NaOH.

[0085] Example 3

[0086] 1. Raw materials of negative electrode electrolyte:

[0087] Zinc-based redox active substance: zinc oxide, used in an amount of 0.3 mol / L in a solvent;

[0088] Supporting electrolyte: NaOH, with a concentration of 3.8 mol / L in the solvent;

[0089] Anthraquinone derivative: 2,6-DHAQ, used at a concentration of 0.015 mol / L in the solvent;

[0090] Solvent: deionized water, 30 mL.

[0091] 2. Preparation of negative electrode electrolyte:

[0092] Weigh NaOH and dissolve it in 30 mL of deionized water. After it is completely dissolved, add zinc oxide and stir until it becomes clear. Then add 2,6-DHAQ and stir to dissolve evenly to obtain a negative electrode electrolyte.

[0093] Negative electrolyte composition: 0.015mol / L 2,6-DHAQ+0.3mol / L[Zn(OH) 4 ] 2- +3.8mol / L NaOH.

[0094] Example 4

[0095] 1. Raw materials of negative electrode electrolyte:

[0096] Zinc-based redox active substance: zinc oxide, used in an amount of 0.3 mol / L in a solvent;

[0097] Supporting electrolyte: NaOH, with a concentration of 3.8 mol / L in the solvent;

[0098] Anthraquinone derivative: 1,4-DHAQ, the concentration in the solvent is 0.015 mol / L;

[0099] Solvent: deionized water, 30 mL.

[0100] 2. Preparation of negative electrode electrolyte:

[0101] Weigh NaOH and dissolve it in 30 mL of deionized water. After it is completely dissolved, add zinc oxide and stir until it becomes clear. Then add 1,4-DHAQ and stir to dissolve evenly to obtain a negative electrode electrolyte.

[0102] Negative electrolyte composition: 0.015mol / L 1,4-DHAQ+0.3mol / L[Zn(OH) 4 ] 2- +3.8mol / L NaOH.

[0103] Comparative Example 1

[0104] The method was carried out in accordance with Example 1, except that the anthraquinone derivative 1,5-DHAQ was replaced by an equimolar amount of the benzoquinone derivative 2,5-dihydroxy-1,4-benzoquinone (DHBQ).

[0105] Product Testing :

[0106] 1. Prepare positive electrolyte for zinc-iron flow battery:

[0107] (1.1) Raw materials:

[0108] Active ingredient: Potassium ferrocyanide K 4 [Fe(CN) 6], the dosage is 0.6 mol / L in solvent; potassium ferrocyanide K 3 [Fe(CN) 6 ], the dosage is 0.05 mol / L in solvent;

[0109] Supporting electrolyte: NaOH, with a concentration of 1.8 mol / L in the solvent;

[0110] Solvent: deionized water, 450 mL.

[0111] (1.2) Preparation:

[0112] Weigh NaOH and dissolve it in 450 mL of deionized water. After it is completely dissolved, add potassium ferrocyanide K 4 [Fe(CN) 6 ] Stir until clear, then add potassium ferrocyanide K 3 [Fe(CN) 6 ], stir and dissolve evenly to obtain the positive electrode electrolyte.

[0113] Positive electrolyte composition: 0.6mol / LK 4 [Fe(CN) 6 ]+0.05mol / LK 3 [Fe(CN) 6 ]+1.8mol / LNaOH.

[0114] 2. Assembling zinc-iron flow battery:

[0115] The stack unit includes:

[0116] Positive electrode: carbon felt;

[0117] Negative electrode: carbon felt;

[0118] Diaphragm: Nafion 117.

[0119] The above-mentioned battery stack unit, the positive electrode storage tank filled with the positive electrode electrolyte obtained in the above-mentioned Section 1 (including Sections 1.1 to 1.2), and the negative electrode storage tank filled with the negative electrode electrolyte are assembled into a zinc-iron liquid flow battery.

[0120] The negative electrode electrolytes of the embodiments and comparative examples were assembled into zinc-iron flow batteries according to the above assembly scheme.

[0121] 3. Assembling zinc-based symmetric flow batteries:

[0122] (3.1) Preparation of negative electrode electrolyte:

[0123] The above methods are implemented according to Examples 1-3 and Comparative Example 1, except that zinc oxide is not added. (Since the negative electrode electrolytes of Examples 1-3 and Comparative Example 1 are different, they are respectively recorded as negative electrode electrolytes S1, S2, S3, and D1 for distinction)

[0124] (3.2) Prepare positive electrolyte:

[0125] 1. Raw materials of positive electrolyte:

[0126] Zinc-based redox active substance: zinc oxide, used in an amount of 0.2 mol / L in a solvent;

[0127] Supporting electrolyte: NaOH, with a concentration of 3.8 mol / L in the solvent;

[0128] Solvent: deionized water, 60 mL.

[0129] 2. Preparation of positive electrolyte:

[0130] Weigh NaOH and dissolve it in 60 mL of deionized water. After it is completely dissolved, add zinc oxide and stir until it becomes clear to obtain a positive electrode electrolyte.

[0131] Positive electrolyte composition: 60mL 0.3mol / L[Zn(OH) 4 ] 2- +3.8mol / L NaOH.

[0132] (3.2) Assembling zinc-based symmetric flow battery:

[0133] The stack unit includes:

[0134] Negative electrode: carbon felt with zinc sheet attached, the mass of the zinc sheet is 0.1 to 2g, and the specific mass is determined according to the battery surface capacity.

[0135] Positive electrode: Carbon felt with zinc sheet attached, the mass of the zinc sheet is 0.3 to 6g, which is 2 to 3 times more than the negative electrode.

[0136] Diaphragm: Nafion 117.

[0137] The above-mentioned battery stack unit, the positive electrode storage tank filled with positive electrode electrolyte, and the negative electrode storage tank filled with negative electrode electrolyte are assembled into a zinc-based symmetrical liquid flow battery.

[0138] 4. Performance test:

[0139] (4.1) Cyclic voltammetry test:

[0140] Cyclic voltammetry tests were performed on the anthraquinone derivatives (i.e., 1,5-DHAQ, 2,6-DHAQ, and 1,8-DHAQ) used in Examples 1-3. The results are as follows: Figure 1As shown. It can be seen that the redox potentials of these anthraquinone derivatives are higher than those of the zinc negative electrode ([Zn(OH) 4 ] 2- ) has a higher redox potential and is suitable for use as an additive to regenerate dead zinc.

[0141] (4.2) Cyclic performance test of zinc-based symmetric flow battery:

[0142] Cycling performance tests were carried out on zinc-based symmetric flow batteries assembled with negative electrolytes S1, S2, S3, and D1, with a test voltage range of 0.6 to -1.4 V and a current density of 20 or 50 mA / cm 2 The charging capacity limit for the first charge and subsequent cycles is set according to the first discharge capacity value to ensure a zinc negative electrode utilization rate close to 100%. Figure 2 As shown in Figure 2, the test current density of the battery using benzoquinone DHBQ in D1 is only 20 mA / cm 2 , while the batteries of the present invention S1-S3 using anthraquinone derivatives (1,5-DHAQ, 2,6-DHAQ, 1,8-DHAQ) at a higher current density (50 mA·cm -2 ) still have longer cycle numbers, among which 1,5-DHAQ has a cycle number of up to 285, showing better dead zinc regeneration ability and long-cycle stability.

[0143] (4.3) Cyclic performance test of zinc-iron flow battery:

[0144] The cycle performance test of the zinc-iron flow battery assembled with the negative electrode electrolyte of the anthraquinone derivative 1,5-DHAQ in Example 1 was carried out, wherein the full battery test voltage range was: 0.5-1.8V, and the current density was: 80mA / cm 2 , the charging capacity limit is set according to the theoretical capacity value corresponding to 75% utilization of the negative electrode electrolyte. At the same time, the zinc-iron flow battery assembled with the negative electrode electrolyte without the introduction of anthraquinone derivatives was used as a blank control sample (i.e., the blank sample in the figure) and the cycle performance test was also carried out. The results are as follows Figure 3 As shown in the figure, the hollow ball line shows the change of Coulomb efficiency with the number of cycles (test condition: current density 80 mA cm -2 ), the solid ball line is the change of surface capacity with the number of cycles (test conditions: surface capacity (capacity / stack reaction area) is 33.2mAh·cm -2 ). It can be seen that the test current density is 80mA·cm -2The corresponding battery of Example 1 can achieve an ultra-long stable cycle of 1200 cycles, and the coulombic efficiency is as high as 99.7%. Compared with the blank control sample, after the anthraquinone derivative is introduced into the present invention, the number of cycles in both the surface capacity and the coulombic efficiency are significantly increased, thereby improving the cycle stability and energy efficiency of the battery.

[0145] (4.4) Cumulative surface capacity of zinc-iron flow battery and capacity contribution of dead zinc:

[0146] The cumulative surface capacity and dead zinc capacity contribution of the zinc-iron flow battery assembled with the negative electrolyte of the anthraquinone derivative 1,5-DHAQ used in Example 1 were calculated. At the same time, the zinc-iron flow battery assembled with the negative electrolyte without the introduction of anthraquinone derivative was used as a blank control sample (i.e., the blank sample in the figure). The calculation method is as follows: Substitute the above Figure 3 The discharge surface capacity of the experimental sample with 1,5-DHAQ added was accumulated cycle by cycle to obtain the cumulative surface capacity performance test results of the assembled zinc-iron liquid flow battery, and compared with the cumulative surface capacity of the blank sample. The difference between the two is the capacity contribution of the dead zinc recycled by the DHAQ additive. The results are as follows: Figure 4 As shown. The red and blue solid circles represent the cumulative surface capacity of the battery with and without the additive, respectively; the red and blue hollow circles represent the cumulative cycle time of the battery with and without the additive, respectively; the yellow shaded area is the capacity contributed by the dead zinc reused from the battery with the additive. It can be seen that the battery of the present invention can achieve a cumulative capacity of 41.21Ah·cm -2 Surface capacity, where the yellow shaded area is the capacity contributed by dead zinc from sample recycling (30.3 Ah·cm -2 , indicating that the introduction of anthraquinone derivatives into the negative electrode electrolyte of the present invention can produce good dead zinc regeneration ability.

[0147] (4.5) High surface capacity cycle performance test of zinc-iron flow battery:

[0148] The volume of the negative electrode electrolyte was changed to 120 mL, and the negative electrode electrolyte of Example 1 was assembled into a high surface capacity (150 mAh cm -2 ) Zinc-iron flow battery, cycle performance test, the results are as follows Figure 5 As shown. It can be seen that the battery shows good dead zinc recycling effect even at high surface capacity.

[0149] (4.6) Capacity-voltage curves of selected cycles (30th, 60th, 90th, 120th) of high-area capacity zinc-iron flow battery:

[0150] The zinc-iron flow battery assembled with the negative electrolyte of Example 1 was tested for charge and discharge. The results are as follows: Figure 6The second discharge platform (1.0-0.8V interval) has a significantly higher capacity than the corresponding first charge platform (1.0-1.4V interval), which corresponds to the targeted reaction between the anthraquinone derivative additive in the negative electrode electrolyte and the dead zinc produced in the battery. This proves that there is a redox targeted reaction between the anthraquinone derivative in the negative electrode electrolyte of the present invention and the dead zinc, thereby realizing the reuse of the dead zinc in the zinc-based flow battery and recovering the lost capacity.

[0151] Specific examples are used herein to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core ideas, including the best mode, and also enable any technician in the field to practice the present invention, including making and using any device or system, and implementing any combined method. It should be pointed out that for ordinary technicians in this technical field, without departing from the principle of the present invention, the present invention can also be improved and modified, and these improvements and modifications also fall within the scope of protection of the claims of the present invention. The scope of patent protection of the present invention is defined by the claims and may include other embodiments that can be thought of by those skilled in the art. If these other embodiments have structural elements similar to the literal expression of the claims, or if they include equivalent structural elements that are not substantially different from the literal expression of the claims, then these other embodiments should also be included in the scope of the claims.

Claims

1. A negative electrode electrolyte for a zinc-iron liquid flow battery, characterized in that: The raw materials for its preparation include: zinc-based redox active material, supporting electrolyte, quinone molecular additive and solvent; Among them, the redox potential of the quinone molecular additive is higher than the redox potential of the zinc negative electrode under the same conditions.

2. The negative electrode electrolyte according to claim 1, characterized in that The quinone molecular additive is an anthraquinone derivative; The anthraquinone derivative is at least one of 1,2-dihydroxyanthraquinone, 1,4-dihydroxyanthraquinone, 1,5-dihydroxyanthraquinone, 1,8-dihydroxyanthraquinone, 2,6-dihydroxyanthraquinone, anthraquinone-2,7-disulfonic acid disodium salt, 4,4'-([9,10-anthraquinone-2,6-diyl]dioxy)dibutyrate, (9,10-dioxy-9,10-dihydroanthracene-2,6-diyl)bis(oxy))bis(propane-3,1-diyl))bis(phosphonic acid), and 3,3'-(9,10-anthraquinonediyl)bis(3-methylbutyric acid).

3. The negative electrode electrolyte according to claim 1, characterized in that The zinc-based redox active material is at least one of zinc oxide, zinc chloride, zinc iodide and zinc bromide.

4. The negative electrode electrolyte according to claim 1, characterized in that The supporting electrolyte is at least one of a soluble metal hydroxide and a metal halide.

5. The negative electrode electrolyte according to claim 4, characterized in that The soluble metal hydroxide is at least one of sodium hydroxide, potassium hydroxide and lithium hydroxide; The metal halide is at least one of sodium chloride, potassium chloride and lithium chloride.

6. The negative electrode electrolyte according to claim 1, characterized in that The solvent is water and / or an organic solvent.

7. The negative electrode electrolyte according to claim 1, characterized in that The concentration of the quinone molecular additive in the solvent is 0.001-0.1 mol / L; The concentration of the zinc-based redox-active substance in the solvent is ≤5 mol / L; The concentration of the supporting electrolyte in the solvent is ≤5 mol / L.

8. A zinc-iron liquid flow battery, characterized in that: include: Battery stack unit; A cathode storage tank, containing cathode electrolyte; A cathode storage tank, containing cathode electrolyte; The negative electrode electrolyte is the negative electrode electrolyte according to any one of claims 1 to 7.

9. The zinc-iron flow battery according to claim 8, characterized in that: The active component of the positive electrode electrolyte is at least one of an iron-based complex, a ferrous-based complex, an iron salt and a ferrous salt.

10. The zinc-iron flow battery according to claim 8, characterized in that: The diaphragm in the stack unit is a perfluorosulfonic acid ion membrane, a sulfonated polyetheretherketone membrane or an Asahi Glass anion membrane.

Images