Neutral zinc ion negative electrode electrolyte, zinc-based flow battery and application

Abstract

The invention provides a neutral zinc ion negative electrode electrolyte, a zinc-based flow battery and application. The neutral zinc ion negative electrode electrolyte comprises a negative electrode active material, a complexing agent and a supporting electrolyte, the zinc-based flow battery comprises a positive electrode electrolyte, a negative electrode electrolyte and a diaphragm. Wherein the complexing agent and zinc ions in the electrolyte form a stable complex, the complex can be used for the zinc-based flow battery, and the size of the complex is larger than that of the pore diameter of a cation exchange membrane in the flow battery. In addition, due to the coordination effect of the complexing agent and zinc ions, the electrochemical potential of the complex is reduced, the battery voltage is increased, meanwhile, the complex carries negative charges, and the electrostatic repulsive force between the complex and a cation exchange membrane in the flow battery is increased. According to the invention, zinc ions are more difficult to pass through the cation exchange membrane in the flow battery, the cycling stability of the neutral zinc-based flow battery is improved, and the battery voltage of the neutral zinc-based flow battery is increased.

Description

Technical Field

[0001] The present invention belongs to the technical field of liquid flow batteries, and in particular relates to a neutral zinc ion negative electrode electrolyte, a zinc-based liquid flow battery and applications. Background Art

[0002] Liquid flow batteries can achieve power and energy decoupling, modular designability, and have the advantages of long-term energy storage and potential low cost. It is a potential candidate for large-scale energy storage. Based on the dual considerations of safety and low cost, zinc-based liquid flow batteries have been a hot topic of research in recent years.

[0003] Due to its low potential, excellent electrochemical kinetics and reversibility, alkaline zinc-based flow batteries have been widely studied. However, alkaline zinc negative electrodes have serious zinc dendrite problems, and the solubility of zinc oxide in alkaline environments is very limited. In large-scale energy storage applications, the volume of the storage tank needs to be increased, which increases the energy storage cost. In contrast, in a neutral environment, zinc salts are used as active substances on the negative electrode side, which have high solubility and a milder neutral environment. Neutral zinc-based flow batteries mainly include zinc-cerium flow batteries, zinc-organic flow batteries, zinc-bromine flow batteries, zinc-iodine flow batteries, and zinc-iron flow batteries. However, neutral zinc-based flow batteries themselves also have some problems that cannot be ignored. First of all, the negative electrode side Zn 2+ It is easy to shuttle through the ion exchange membrane to the positive electrode, causing self-discharge and irreversible capacity decay, and reducing the cycle stability of the battery. In zinc-bromine, zinc-iodine and other systems, there is an obvious problem of mutual shuttling between the positive and negative electrodes because the zinc ions have opposite charges to the bromide ions and iodide ions. Although the use of high-concentration mixed electrolytes can balance the migration of active substances, it reduces the utilization rate of the electrolyte and increases the cost of the electrolyte. Secondly, compared with zincate, the negative electrode active material of alkaline zinc-based flow batteries, the redox potential of zinc ions is more positive, resulting in a lower voltage for neutral zinc-based flow batteries. Finally, there are also problems on the negative electrode side of neutral zinc-based flow batteries, such as zinc dendrites and hydrogen evolution side reactions that cannot be ignored.

[0004] The document with patent publication number CN118156572A discloses a neutral zinc-iron flow battery using [Fe(CN)6] 4- / 3-As the positive electrode active material, zinc salt is used as the negative electrode active material. By adding sodium citrate, sodium nitrilotriacetate, and tetrasodium ethylenediaminetetraacetate to the negative electrode electrolyte to form a metal complex with zinc ions, the migration behavior of zinc ions to the positive electrode is inhibited based on the "Donnan exclusion" effect. The cycle stability and battery efficiency of the flow battery constructed by adding sodium citrate have been effectively improved. However, during the operation of the battery, both the voltage efficiency and energy efficiency have been significantly attenuated. And there is no regulating effect on the battery voltage. And when the unpotassium-treated sulfonated polyetheretherketone membrane is used as a diaphragm, the cycle performance of the battery decreases significantly, indicating that the complexation between sodium citrate and zinc ions is relatively weak, and there are still many uncomplexed zinc ions in the negative electrode electrolyte. Summary of the invention

[0005] The present invention provides a neutral zinc ion negative electrode electrolyte, a zinc-based liquid flow battery and its application, wherein a complexing agent with strong coordination ability is added to the negative electrode electrolyte to enhance the interaction between zinc ions and the complexing agent, thereby improving the cycle stability and battery voltage of the battery. The energy efficiency and voltage efficiency can remain stable during the cycle process.

[0006] The technical solution provided by the present invention is as follows:

[0007] A neutral zinc ion negative electrode electrolyte according to an embodiment of the present invention comprises: a positive electrode electrolyte, a negative electrode electrolyte and a separator;

[0008] The positive electrode electrolyte comprises a positive electrode active material and a supporting electrolyte;

[0009] The negative electrode electrolyte comprises a negative electrode active material, a complexing agent and the supporting electrolyte;

[0010] The complexing agent comprises one or more of diethylenetriaminepentaacetic acid, propylenediaminetetraacetic acid, gluconic acid, hydroxyethylethylenediaminetriacetic acid, dihydroxyethylglycine, polyacrylic acid, polymethacrylic acid, ethylenediaminedisuccinic acid, succinic acid, cyclohexanetetraacetic acid, ethylene glycol diethyl ether diaminetetraacetic acid, N-hydroxyethylethylenediaminetriacetic acid, iminodiacetic acid, and diethylenetriaminepentaacetic acid salt, propylenediaminetetraacetic acid salt, gluconate, hydroxyethylethylenediaminetriacetic acid salt, dihydroxyethylglycine salt, polyacrylate, polymethacrylate, ethylenediaminedisuccinic acid salt, succinate, cyclohexanetetraacetic acid salt, ethylene glycol diethyl ether diaminetetraacetic acid salt, N-hydroxyethylethylenediaminetriacetic acid salt and iminodiacetic acid salt;

[0011] Among them, the chelating agent forms a stable complex with zinc ions, the size of the complex is larger than the pore size of the cation exchange membrane in the zinc-iron liquid flow battery, making it difficult for it to pass through the ion exchange membrane. The chelating agent makes the complex have a negative charge, and the negative charge of the complex can produce charge repulsion with the anions on the diaphragm of the zinc-based liquid flow battery. Based on the above two effects, the migration of zinc ions to the positive electrode is inhibited, and the electrostatic repulsion between the complex and the cation exchange membrane in the zinc-iron liquid flow battery is increased.

[0012] In an optional embodiment, the concentration of the active substance in the positive electrode electrolyte is 0.4 molL -1 -5molL -1 .

[0013] In an optional embodiment, the negative electrode active material is a zinc salt, and the zinc salt includes one of zinc bromide, zinc chloride, zinc trifluoromethanesulfonate, zinc sulfate and zinc acetate.

[0014] In an optional embodiment, in the negative electrode electrolyte, the concentration of the zinc salt is 0.2 molL -1 -2molL -1 .

[0015] In an optional embodiment, the molar ratio of the zinc salt to the complexing agent is 1:0.5 to 1:2.

[0016] In an optional embodiment, the supporting electrolyte can be sodium chloride, potassium chloride, a mixture of sodium chloride and potassium chloride, sodium sulfate, potassium sulfate, a mixture of sodium sulfate and potassium sulfate, sodium iodide, potassium iodide, a mixture of sodium iodide and potassium iodide, sodium bromide, potassium bromide, a mixture of sodium bromide and potassium bromide.

[0017] In an optional embodiment, the concentration of the supporting electrolyte is 0.4 molL -1 ~3molL -1 .

[0018] In an optional embodiment, the pH value of the negative electrode electrolyte is 5-10; the pH value of the positive electrode electrolyte is 5-10.

[0019] In an optional embodiment, the membrane is a sulfonated polyetheretherketone membrane, a perfluorosulfonic acid membrane or a polybenzimidazole membrane.

[0020] On the other hand, a zinc-based liquid flow battery is also provided, the zinc-based liquid flow battery comprising: any one of the above-mentioned neutral zinc ion negative electrode electrolyte, positive electrode electrolyte, and a diaphragm;

[0021] The positive electrode electrolyte includes a positive electrode active material, and the positive electrode active material includes sodium ferrocyanide, potassium ferrocyanide, ammonium ferrocyanide, a mixture of sodium ferrocyanide and potassium ferrocyanide; or a mixture of potassium ferrocyanide and ammonium ferrocyanide;

[0022] or ferric chloride;

[0023] or one or more of zinc iodide, potassium iodide, sodium iodide;

[0024] Or one or more of water-soluble 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO) derivatives.

[0025] In yet another aspect, an application of a zinc-based liquid flow battery is provided, comprising applying the zinc-based liquid flow battery to a fuel cell.

[0026] The neutral zinc ion negative electrode electrolyte, zinc-based liquid flow battery and application provided by the embodiments of the present invention have at least the following beneficial effects:

[0027] The neutral zinc ion negative electrode electrolyte provided by the embodiment of the present invention, by selecting a suitable complexing agent, based on the complexing agent provided by the embodiment of the present invention carrying more negative charge, after forming a complex with zinc ions, the complex is given more negative charge, and in addition, compared with zinc ions, the size of the complex is increased, making it difficult to pass through the ion exchange membrane. The coordination effect of the complexing agent and zinc ions reduces the electrochemical potential of the complex, increases the battery voltage, and increases the battery voltage of the neutral zinc-based flow battery. The complex carries more negative charge, which increases the electrostatic repulsion between the complex and the ion exchange membrane in the neutral zinc-based flow battery, enhancing the Donnan effect (the Donnan effect is based on the Donnan equilibrium and is used to describe the desalination process of the charged membrane. The Donnan equilibrium model is that when a membrane with charged groups is placed in a salt-containing solvent, the concentration of counterions in the solution (ions with a charge opposite to the fixed charge in the membrane) in the membrane is greater than that in the bulk solution, while the concentration of ions with the same name in the membrane is lower than that in the bulk solution. The Donnan potential difference thus formed prevents the diffusion of ions with the same name from the bulk solution into the membrane. In order to maintain electrical neutrality, the counterions are also retained by the membrane.), the formed complex has a larger volume and a stronger size exclusion effect, making it more difficult for the complex to pass through the ion exchange membrane in the neutral zinc-based flow battery, thereby improving the cycle stability of the neutral zinc-based flow battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The above and other objects, features and advantages of the present disclosure will become more apparent through a more detailed description of exemplary embodiments of the present disclosure in conjunction with the accompanying drawings, wherein like reference numerals generally represent like components throughout the exemplary embodiments of the present disclosure. Figure 1This is a discharge capacity-Coulomb efficiency diagram of the neutral zinc-iron flow battery after 200 cycles in Example 1 of the present application.

[0029] Figure 2 This is the charge and discharge curve of the battery in Example 1 of the present application at the 200th cycle.

[0030] Figure 3 This is a discharge capacity-coulombic efficiency diagram of the battery after 70 cycles in Example 2 of the present application.

[0031] Figure 4 This is a discharge capacity diagram of the battery cycle in Comparative Example 1 of the present application. DETAILED DESCRIPTION

[0032] Embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although embodiments of the present disclosure are shown in the accompanying drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided to make the present disclosure more thorough and complete, and to fully convey the scope of the present disclosure to those skilled in the art.

[0033] As used herein, the term "including" and its variations mean open inclusion, i.e., "including but not limited to". Unless otherwise stated, the term "or" means "and / or". The term "based on" means "based at least in part on". The terms "an example embodiment" and "an embodiment" mean "at least one example embodiment". The term "another embodiment" means "at least one additional embodiment". The terms "first", "second", etc. may refer to different or the same objects. Other explicit and implicit definitions may also be included below.

[0034] The embodiment of the present invention provides a neutral zinc ion negative electrode electrolyte, comprising: the neutral zinc ion negative electrode electrolyte comprises a negative electrode active material, a complexing agent and a supporting electrolyte; the complexing agent comprises one or more of diethylenetriaminepentaacetic acid, propylenediaminetetraacetic acid, gluconic acid, hydroxyethylethylenediaminetriacetic acid, dihydroxyethylglycine, polyacrylic acid, polymethacrylic acid, ethylenediaminedisuccinic acid, succinic acid, cyclohexanetetraacetic acid, ethylene glycol diethyl ether diaminetetraacetic acid, N-hydroxyethylethylenediaminetriacetic acid, iminodiacetic acid and diethylenetriaminepentaacetate, propylenediaminetetraacetate, gluconate, hydroxyethylethylenediaminetriacetate, dihydroxyethylglycine, polyacrylate, polymethacrylate, ethylenediaminedisuccinate, succinate, cyclohexanetetraacetate, ethylene glycol diethyl ether diaminetetraacetate, N-hydroxyethylethylenediaminetriacetate and iminodiacetate;

[0035] Among them, the chelating agent forms a stable complex with the zinc ions in the zinc-iron flow battery, and the size of the complex is larger than the pore size of the cation exchange membrane in the zinc-iron flow battery. The chelating agent increases the negative charge of the complex, thereby increasing the electrostatic repulsion between the complex and the ion exchange membrane in the neutral zinc-based flow battery.

[0036] The neutral zinc-based flow battery provided by the embodiment of the present invention is based on the use of the above-mentioned neutral zinc ion negative electrode electrolyte, and by selecting a suitable complexing agent, the complexing agent provided by the embodiment of the present invention carries more negative charge, and after forming a complex with the zinc ions in the neutral zinc-iron flow battery, the complex is given more negative charge. In addition, compared with the zinc ions, the size of the complex is increased, making it difficult to pass through the ion exchange membrane. The coordination effect of the complexing agent and the zinc ions reduces the electrochemical potential of the complex, increases the battery voltage, and increases the battery voltage of the neutral zinc-based flow battery. The complex carries more negative charge, which increases the electrostatic repulsion between the complex and the ion exchange membrane in the neutral zinc-based zinc-iron flow battery, enhancing the Donnan effect (the Donnan effect is based on the Donnan equilibrium and is used to describe the desalination process of the charged membrane. The Donnan equilibrium model is that when a membrane with charged groups is placed in a salt-containing solvent, the concentration of counterions in the solution (ions with a charge opposite to the fixed charge in the membrane) in the membrane is greater than that in the bulk solution, while the concentration of ions with the same name in the membrane is lower than that in the bulk solution. The Donnan potential difference thus formed prevents the diffusion of ions with the same name from the bulk solution into the membrane. In order to maintain electrical neutrality, the counterions are also retained by the membrane). The formed complex has a larger volume and a stronger size exclusion effect, making it more difficult for the complex to pass through the ion exchange membrane in the zinc-iron flow battery, thereby improving the cycle stability of the neutral zinc-based flow battery and increasing the battery voltage of the neutral zinc-based flow battery.

[0037] The neutral zinc-iron flow battery provided by the embodiment of the present invention has a stronger coordination between the complexing agent and the zinc ion in the neutral zinc ion negative electrode electrolyte, so that the complex has a lower redox potential, thereby improving the energy density of the zinc-iron flow battery. In addition, the raw materials required for the positive and negative electrolytes of the neutral zinc-iron flow battery provided by the embodiment of the present invention are cheap and easy to obtain, the operating conditions are mild, the operation is simple, and it has the advantages of low cost, high energy density, and long cycle life.

[0038] It should be noted that the neutral zinc-iron liquid flow battery provided by the present invention operates under near-neutral conditions (eg, PH=7), and the positive and negative electrode active materials have higher solubility, which can improve the energy density of the zinc-iron liquid flow battery.

[0039] In an optional embodiment, the positive electrode active material and the positive electrode electrolyte include a positive electrode active material, and the positive electrode active material includes sodium ferrocyanide, potassium ferrocyanide, ammonium ferrocyanide, a mixture of sodium ferrocyanide and potassium ferrocyanide; or a mixture of potassium ferrocyanide and ammonium ferrocyanide; or ferric chloride; or one or more of zinc iodide, potassium iodide, and sodium iodide; or one or more of water-soluble 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO) derivatives.

[0040] Exemplarily, the positive electrode active material may be sodium ferrocyanide, potassium ferrocyanide, ammonium ferrocyanide, ferrous chloride, zinc bromide, potassium bromide, zinc iodide, potassium iodide. It may also be a mixture of sodium ferrocyanide and potassium ferrocyanide, a mixture of sodium ferrocyanide and ammonium ferrocyanide, a mixture of potassium ferrocyanide and ammonium ferrocyanide, a mixture of zinc bromide and potassium bromide, a mixture of zinc iodide and sodium iodide, and the mixing ratio may be 1:1.

[0041] In an optional embodiment, the negative electrode active material includes a zinc salt, and the zinc salt includes one of zinc bromide, zinc chloride, zinc trifluoromethanesulfonate, zinc sulfate and zinc acetate.

[0042] In an optional embodiment, the concentration of zinc salt in the negative electrode electrolyte is 0.2 molL -1 -2molL -1 .

[0043] For example, the concentration of the zinc salt, that is, zinc bromide, zinc chloride, zinc trifluoromethanesulfonate, zinc sulfate or zinc acetate, can be 0.2 mol / L -1 , 0.3molL -1 , 0.4molL -1 , 0.5molL -1 , 0.6molL -1 , 0.7molL -1 , 0.8molL -1 , 0.9molL -1 , 1.0molL -1 , 1.1molL -1 , 1.2molL -1 , 1.3molL -1 、1.4molL -1 , 1.5molL -1 , 1.6molL -1 、1.7molL -1 、1.8molL -1 、1.9molL -1 or 2molL -1 wait.

[0044] In an optional embodiment, the molar ratio of zinc salt to complexing agent is 1:0.5 to 1:2.

[0045] For example, the molar ratio of zinc salt to complexing agent can be 1:0.5, 1:0.6, 1:0.7, 1:0.8, 1:0.9 or 1:2, etc.

[0046] In an optional embodiment, the supporting electrolyte may be sodium chloride, potassium chloride, a mixture of sodium chloride and potassium chloride, sodium sulfate, potassium sulfate, a mixture of sodium sulfate and potassium sulfate, sodium iodide, potassium iodide, a mixture of sodium iodide and potassium iodide, sodium bromide, potassium bromide, a mixture of sodium bromide and potassium bromide.

[0047] Exemplarily, the supporting electrolyte may be sodium chloride or potassium chloride alone, or a mixture of sodium chloride or potassium chloride. It may be sodium bromide or potassium bromide alone, or a mixture of sodium bromide and potassium bromide. Exemplarily, when the supporting electrolyte is a mixture of sodium chloride or potassium chloride, the mixing ratio may be 1:2.

[0048] In an optional embodiment, the concentration of the supporting electrolyte is 0.4 mol / L -1 ~4mol / L -1 .

[0049] For example, the concentration of the supporting electrolyte can be sodium chloride or potassium chloride alone, or a mixture of sodium chloride or potassium chloride. It can be sodium bromide or potassium bromide alone, or a mixture of sodium bromide and potassium bromide. It can be 0.4 mol / L -1 , 0.5molL -1 , 0.6molL -1 , 0.7molL -1 , 0.8molL -1 , 0.9molL -1 , 1.0molL -1 , 1.1molL -1 , 1.2molL -1 , 1.3molL -1 、1.4molL -1 , 1.5molL -1 , 1.6molL -1 、1.7molL -1 、1.8molL -1 、1.9molL -1 , 2molL -1 、3.0molL -1 、3.1molL -1 、3.2molL -1 、3.3molL -1、3.4molL -1 、3.5molL -1 、3.6molL -1 、3.7molL -1 、3.8molL -1 、3.9molL -1 or 4 molL -1 wait.

[0050] In an optional embodiment, the pH value of the negative electrode electrolyte is 5-10; the pH value of the positive electrode electrolyte is 5-10.

[0051] Illustratively, the pH of the negative electrode electrolyte may be 5, 6, 7, 8, 9 or 10; the pH of the positive electrode electrolyte may be 5, 6, 7, 8, 9 or 10.

[0052] In an optional embodiment, the membrane is a sulfonated polyetheretherketone membrane, a perfluorosulfonic acid membrane or a polybenzimidazole membrane.

[0053] The neutral zinc-iron flow battery of the present invention will be further explained and described below through optional embodiments.

[0054] Example 1

[0055] Negative electrolyte: The complexing agent is 1,3PDTA (1,3-propylenediaminetetraacetic acid), in which the molar ratio of 1,3PDTA acid ligand and zinc ion is 1:1, and the zinc salt concentration is 0.4 molL -1 The supporting electrolyte is sodium chloride with a concentration of 2 mol / L -1 , use sodium hydroxide to adjust the pH of the negative electrode electrolyte to 7.

[0056] Positive electrolyte: Potassium ferrocyanide and sodium ferrocyanide are prepared in a 1:1 molar ratio, and the concentrations of K4[Fe(CN)6] and Na4[Fe(CN)6] are both 0.4 mol / L -1 The supporting electrolytes are sodium chloride and potassium chloride, with a concentration of 0.4 mol / L -1 .

[0057] Ion exchange membrane (membrane described in the present invention): The selected ion exchange membrane is a membrane of model Nafion 117.

[0058] Nafion membrane (diaphragm) treatment: heated with 5%wt hydrogen peroxide at 80°C for 2 hours, then -1 Sulfuric acid was heated at 80°C for 2 hours and then 1 mol L -1 The sodium chloride solution was heated at 80°C for 1 hour.

[0059] Battery assembly: positive electrode stainless steel end plate, fluorine rubber pad, rubber ring, copper plate, graphite plate current collector are stacked in sequence, with an area of ​​3.3×3.3cm 2 , and the carbon felt cathode is 3 mm thick, and the Nafion 117 membrane after sodium treatment is used as the separator, with an area of ​​3.3 × 3.3 cm 2 , and a 3mm thick carbon felt negative electrode, a graphite plate current collector, a copper plate, an rubber ring, a fluorine rubber pad, a negative electrode side stainless steel end plate. The electrolyte storage tank and pump and pipeline are assembled according to the conventional liquid flow battery structure and assembly process.

[0060] The constant current charge and discharge mode was used for testing at 40 mA cm -2 The current density was 40 mAh cm -2 Constant capacity charging, discharge to 0.5V at this current density. The cycle performance of the prepared neutral zinc-iron flow battery can be found in Figure 1 .

[0061] Example 2

[0062] Negative electrolyte composition: 40mL molar concentration 0.8molL -1 ZnBr2, 0.8 mol L -1 PDTA and 2.0 mol L -1 The pH of the negative electrolyte was adjusted to 7 by adding NaOH.

[0063] Positive electrolyte composition: 300mL molar concentration 0.6molL -1 K4[Fe(CN)6], 0.6molL -1 of Na4[Fe(CN)6] and 0.4molL -1 NaCl and 0.4 molL -1 of KCl.

[0064] The battery assembly method and the Nafion membrane treatment method were the same as those in Example 1. The constant current charge and discharge mode was used for testing. -2 The current density was 80 mAh cm -2 Constant capacity charging, discharge to 0.5V at this current density. The cycle performance of the prepared neutral zinc-iron flow battery can be found in Figure 2 .

[0065] Example 3

[0066] Negative electrolyte composition: 40mL molar concentration 0.4molL -1 ZnAc2, 0.4 mol L -1 of sodium gluconate and 2.0 molL -1 of NaCl.

[0067] Positive electrolyte composition: 300mL molar concentration 0.6mol L -1 K4[Fe(CN)6], 0.6 mol L -1 of Na4[Fe(CN)6] and 0.4 mol L -1 NaCl + 0.4 mol L -1 of KCl.

[0068] The battery assembly method and the treatment method of the Nafion membrane were the same as those in Example 1. The constant current charge and discharge mode was used for testing. -2 The current density was 40 mAh cm -2 Charge at constant capacity and discharge to 0.5V at this current density.

[0069] Comparative Example 1

[0070] Negative electrolyte composition: 40mL molar concentration 0.4molL -1 ZnBr2, 2.0molL -1 of NaCl.

[0071] Positive electrolyte composition: 200mL molar concentration 0.4molL -1 K4[Fe(CN)6], 0.4molL -1 of Na4[Fe(CN)6] and 0.4molL -1 NaCl and 0.4 molL -1 of KCl.

[0072] The battery assembly method and the treatment method of the Nafion membrane were the same as those in Example 1. The constant current charge and discharge mode was used for testing. -2 The current density was 40 mAh cm -2 Charge at constant capacity and discharge to 0.5V at this current density.

[0073] Please see Figure to Figure 4 , Figure 1 This is a discharge capacity-Coulomb efficiency diagram of the neutral zinc-iron flow battery after 200 cycles in Example 1 of the present application. Figure 2 This is the charge and discharge curve of the battery in Example 1 of the present application at the 200th cycle. Figure 3 This is a discharge capacity-coulombic efficiency diagram of the battery after 70 cycles in Example 2 of the present application. Figure 4 This is a discharge capacity diagram of the battery cycle in Comparative Example 1 of the present application.

[0074] from Figure 1It can be seen that by adding a chelating agent to the negative electrode electrolyte, the constructed neutral zinc-iron flow battery has good cycle stability and high coulombic efficiency.

[0075] from Figure 2 It can be seen that the addition of the complexing agent does not significantly increase the polarization of the battery. In addition, due to the strong coordination effect of the complexing agent, the potential of the zinc negative electrode is lower, and the neutral zinc-iron flow battery presents a higher voltage.

[0076] from Figure 3 It can be seen that after the introduction of the complexing agent, the neutral zinc-iron flow battery still has good cycle stability and high coulombic efficiency at high concentration of active substances, high surface capacity and high current density, and is suitable for large-scale applications.

[0077] from Figure 4 Judging from the battery cycle results of Comparative Example 1, in the zinc-iron liquid flow battery without the addition of a chelating agent, due to the migration of zinc ions to the positive electrode, a side reaction occurred to produce precipitation, resulting in very poor cycle stability of the neutral zinc-iron liquid flow battery, which could hardly operate normally.

[0078] The embodiments of the present disclosure have been described above, and the above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Many modifications and changes will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments. The selection of terms used herein is intended to best explain the principles of the embodiments, practical applications, or technical improvements in the market, or to enable other persons of ordinary skill in the art to understand the embodiments disclosed herein.

Claims

1. A neutral zinc ion negative electrode electrolyte, characterized in that, The neutral zinc ion negative electrode electrolyte comprises a negative electrode active material, a complexing agent and a supporting electrolyte; The complexing agent is one or more of diethylenetriaminepentaacetic acid, propylenediaminetetraacetic acid, gluconic acid, hydroxyethylethylenediaminetriacetic acid, dihydroxyethylglycine, polyacrylic acid, polymethacrylic acid, ethylenediaminedisuccinic acid, succinic acid, cyclohexanetetraacetic acid, ethylene glycol diethyl ether diaminetetraacetic acid, N-hydroxyethylethylenediaminetriacetic acid, iminodiacetic acid, and diethylenetriaminepentaacetic acid salt, propylenediaminetetraacetic acid salt, gluconate, hydroxyethylethylenediaminetriacetic acid salt, dihydroxyethylglycine salt, polyacrylate, polymethacrylate, ethylenediaminedisuccinic acid salt, succinate, cyclohexanetetraacetic acid salt, ethylene glycol diethyl ether diaminetetraacetic acid salt, N-hydroxyethylethylenediaminetriacetic acid salt and iminodiacetic acid salt; Among them, the complexing agent forms a stable complex with zinc ions, the size of the complex is larger than the pore size of the cation exchange membrane in the zinc-iron liquid flow battery, making it difficult for it to pass through the ion exchange membrane, and the complexing agent makes the complex have a negative charge. The negative charge of the complex and the anions on the diaphragm of the zinc-based liquid flow battery can produce charge repulsion, inhibiting the migration of zinc ions to the positive electrode, and the electrostatic repulsion between the complex and the cation exchange membrane in the zinc-iron liquid flow battery is increased.

2. The neutral zinc ion negative electrode electrolyte according to claim 1, characterized in that The negative electrode active material is a zinc salt, and the zinc salt includes one or more of zinc bromide, zinc chloride, zinc trifluoromethanesulfonate, zinc sulfate and zinc acetate.

3. The neutral zinc ion negative electrode electrolyte according to claim 2, characterized in that In the negative electrode electrolyte, the concentration of the zinc salt is 0.2 molL -1 -2molL -1 .

4. The neutral zinc ion negative electrode electrolyte according to claim 2, characterized in that The molar ratio of the zinc salt to the complexing agent is 1:0.5 to 1:

2.

5. The neutral zinc ion negative electrode electrolyte according to claim 1, characterized in that The supporting electrolyte is one of sodium chloride, potassium chloride, a mixture of sodium chloride and potassium chloride, sodium sulfate, potassium sulfate, a mixture of sodium sulfate and potassium sulfate, sodium iodide, potassium iodide, a mixture of sodium iodide and potassium iodide, sodium bromide, potassium bromide, and a mixture of sodium bromide and potassium bromide.

6. The neutral zinc ion negative electrode electrolyte according to claim 5, characterized in that: The concentration of the supporting electrolyte is 0.4 molL -1 ~3molL -1 .

7. The neutral zinc ion negative electrode electrolyte according to claim 1, characterized in that The pH of the negative electrode electrolyte is 5-10.

8. The neutral zinc ion negative electrode electrolyte, zinc-based flow battery and application according to claim 1, characterized in that: The diaphragm is a sulfonated polyetheretherketone membrane, a perfluorosulfonic acid membrane or a polybenzimidazole membrane.

9. A zinc-based flow battery, characterized in that: The zinc-based liquid flow battery comprises: a neutral zinc ion negative electrode electrolyte, a positive electrode electrolyte, and a diaphragm as described in any one of claims 1 to 8; The positive electrode electrolyte includes a positive electrode active material, and the positive electrode active material includes sodium ferrocyanide, potassium ferrocyanide, ammonium ferrocyanide, a mixture of sodium ferrocyanide and potassium ferrocyanide; or a mixture of potassium ferrocyanide and ammonium ferrocyanide; or ferric chloride; or one or more of zinc iodide, potassium iodide, sodium iodide; Or one or more of water-soluble 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO) derivatives.

10. An application of a zinc-based flow battery, characterized in that: The invention comprises applying the zinc-based liquid flow battery to a fuel cell.

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