Electrolyte and preparation method, zinc-iron flow battery, electric device and energy storage device

Abstract

The application relates to an electrolyte and a preparation method thereof, a zinc-iron flow battery, a power utilization device and an energy storage device. The components of the electrolyte include ferrocyanide, alkali, a catalyst and water. The catalyst includes a compound with the following structural formula: wherein each R is independently 4-carboxyl phenyl, 4-sulfonic acid phenyl, 4-amino phenyl or 4-phosphorous acid; and M is iron (III), cobalt (II), manganese (II) or nickel (II). The electrolyte is beneficial to electron and proton transfer, can effectively reduce an electrochemical reaction energy barrier, thereby improving an electrochemical reaction rate and ionic conductivity, and further improving battery energy efficiency and reducing voltage loss.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of batteries, in particular to an electrolyte and a preparation method thereof, a zinc-iron flow battery, an electric device and an energy storage device. BACKGROUND

[0002] The alkaline zinc-iron flow battery using alkaline electrolyte is one of the long-time energy storage batteries with great application prospects in the field of flow batteries, which has the advantages of high energy density, long cycle life, low electrolyte cost and safety and environmental protection. However, the current alkaline zinc-iron flow battery has the problems of large voltage loss and low energy efficiency. SUMMARY

[0003] Therefore, it is necessary to provide an electrolyte and a preparation method thereof, a zinc-iron flow battery, an electric device and an energy storage device capable of reducing voltage loss and improving energy efficiency.

[0004] In one aspect of the present application, an electrolyte is provided, and components of the electrolyte include ferrocyanide, base, catalyst and water; the catalyst includes a compound with the following structural formula:

[0005]

[0006] wherein R is 4-carboxyphenyl, 4-sulfonic acid phenyl, 4-aminophenyl or 4-phosphorus acid; M is iron (III), cobalt (II), manganese (II) or nickel (II).

[0007] The above-mentioned electrolyte is beneficial to electron and proton transfer, thereby improving the electrochemical reaction rate and ionic conductivity, and further improving the energy efficiency of the battery and reducing the voltage loss.

[0008] The metalloporphyrin has a macrocyclic conjugated structure, and a complex formed by the macrocyclic conjugated structure and iron, cobalt, manganese or nickel metal ions can not only achieve homogeneous catalysis, but also effectively reduce the electrochemical reaction energy barrier between the ferrocyanide ions and the ferricyanide ions, so that the conversion between the ferrocyanide ions and the ferricyanide ions is faster and more efficient. The 4-carboxyphenyl, 4-sulfonic acid phenyl, 4-aminophenyl and 4-phosphite on the metalloporphyrin not only have hydrophilicity, but also can reduce the surface energy of the electrode, improve the wettability of the electrolyte to the electrode, so that the electrolyte can also be uniformly distributed at the electrode interface, and promote homogeneous catalysis. The main role of the base in the electrolyte is to provide an ion-conducting medium, maintain the ion balance inside the battery, and ensure the normal operation of the battery; under alkaline conditions, the iron ions in the ferrocyanide salt undergo redox reaction to realize the charging and discharging process of the battery, and the metalloporphyrin is uniformly distributed in the electrolyte, which reduces the concentration gradient, so that the redox reaction is carried out in a more uniform environment. The three-way interaction of ferrocyanide, base and metalloporphyrin synergistically improves the energy efficiency and voltage efficiency of the battery and reduces the voltage loss of the battery.

[0009] The catalyst in the electrolyte does not need to be loaded on the positive electrode or the negative electrode, which avoids the problem of catalyst failure caused by falling off and loss of the supported catalyst during long-term cycling.

[0010] The zinc-iron flow battery prepared by using the above electrolyte as the positive electrode electrolyte not only has high energy efficiency and small voltage loss, but also has the advantages of high energy density, long cycle life, low electrolyte cost and safety and environmental protection.

[0011] In some embodiments, the catalyst includes at least one of manganese (II) tetra(4-sulfonic acid phenyl) porphyrin, iron (III) tetra(4-phosphite) porphyrin, cobalt (II) tetra(4-carboxyphenyl) porphyrin and nickel (II) tetra(4-aminophenyl) porphyrin.

[0012] In some embodiments, the molar concentration ratio of the catalyst to the ferrocyanide ions in the ferrocyanide salt is 0.01% to 0.1%.

[0013] In some embodiments, the concentration of the ferrocyanide ions in the electrolyte is 0.2 mol / L to 1.60 mol / L.

[0014] In some embodiments, the concentration of the base is 1.0 mol / L to 6.0 mol / L.

[0015] In some embodiments, the ferrocyanide salt includes at least one of sodium ferrocyanide and potassium ferrocyanide.

[0016] In some embodiments, the base includes at least one of sodium hydroxide, potassium hydroxide, and lithium hydroxide.

[0017] In some embodiments, the electrolyte satisfies at least one of the following conditions:

[0018] (1) the components of the electrolyte include sodium ferrocyanide, potassium hydroxide, manganese (II) tetra(4-sulfonatophenyl)porphyrin, and water;

[0019] (2) the components of the electrolyte include potassium ferrocyanide, sodium hydroxide, iron (III) tetra(4-phosphonato)porphyrin, and water.

[0020] In a second aspect of the present application, a method for preparing an electrolyte is provided, which comprises mixing the base, the ferrocyanide salt, and the catalyst in water to obtain the electrolyte.

[0021] In some embodiments, the mixing of the base, the ferrocyanide salt, and the catalyst in water comprises the following steps:

[0022] First, the base is dissolved in water to obtain a base solution;

[0023] Then, the ferrocyanide salt and the catalyst are mixed in the base solution to obtain the electrolyte.

[0024] In a third aspect of the present application, a zinc-iron flow battery is provided, which comprises a positive electrolyte, wherein the positive electrolyte is the electrolyte prepared according to the first aspect or the method according to the second aspect.

[0025] In a fourth aspect of the present application, an electrical device is provided, which comprises the zinc-iron flow battery according to the third aspect.

[0026] In a fifth aspect of the present application, an energy storage device is provided, which comprises the zinc-iron flow battery according to the third aspect. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 The figure is the relationship curve between the cycle number and the coulombic efficiency, voltage efficiency, and energy efficiency of the battery system in Comparative Example 1.

[0028] Figure 2 The figure is the relationship curve between the cycle number and the coulombic efficiency, voltage efficiency, and energy efficiency of the battery system in Comparative Example 1.

[0029] Figure 3 The figure is the charge-discharge curve of the battery system in Comparative Example 1.

[0030] Figure 4 The figure is the charge-discharge curve of the battery system in Comparative Example 1. DETAILED DESCRIPTION

[0031] For the purposes of this disclosure, reference will be made to the accompanying drawings which form a part of the disclosure. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the application. The embodiments of the application illustrated herein are by way of example only and not limitation, and thus the application should not be limited to the embodiments disclosed with in the scope of the description.

[0032] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in the description of the application herein is for describing particular embodiments only and is not intended to be limiting of the application. All publications, patent applications, patents, and other references mentioned herein are incorporated by reference in their entirety for the teachings relevant to the sentence and / or paragraph in which the reference is presented.

[0033] Zinc-iron flow battery generally uses zinc ions as negative active ions and iron ions as positive active ions. The commonly used positive electrolyte includes chloride system, sulfate system and sulfonate system. Chloride ions in the chloride system have strong corrosiveness, which has high corrosion resistance requirements for the electrode materials and battery components of the battery, and may reduce the service life and reliability of the battery. Compared with the chloride system, the conductivity of the sulfate system is relatively low, which may limit the charge-discharge performance of the battery at high current density. The preparation cost of the electrolyte of the iron salt of the sulfonate system is relatively high, which limits its large-scale application. In addition, the electrolyte of some sulfonate systems may have the problem of high viscosity at high concentration, which affects ion transmission and battery performance. There is also a zinc-iron flow battery positive electrolyte active substance composed of water, ferrocyanide and strong base. However, the electrochemical reaction energy barrier of ferrocyanide and ferricyanide in the mutual conversion process is high, and the reaction rate is slow, which causes the problems of large voltage loss and low energy efficiency of the battery. At present, researchers improve the positive electrode reaction rate by loading metal-nitrogen-carbon catalyst on the electrode. The advantage of this method is targeted catalysis, and the disadvantage is that the catalyst loaded on the surface of the electrode is not firm, and the catalyst loaded on the surface of the electrode is easy to lose and fall off and lose the catalytic effect with the progress of the battery charge and discharge and the flushing of the fluid.

[0034] Based on this, the first aspect of the application provides an electrolyte, the components of the electrolyte include ferrocyanide, base, catalyst and water; the catalyst includes a compound with the following structural formula:

[0035]

[0036] wherein R is 4-carboxyphenyl, 4-sulfonic acid phenyl, 4-aminophenyl or 4-phosphorus acid; M is iron (III), cobalt (II), manganese (II) or nickel (II).

[0037] It is understood that the four R on the same catalyst are the same or different. Alternatively, the four R on the same catalyst are the same. The catalyst is a compound of the above structural formula, which can be one or more compounds conforming to the above structural formula.

[0038] It is understood that M is a trivalent iron ion, a divalent cobalt ion, a divalent manganese ion or a divalent nickel ion.

[0039] The above electrolyte is conducive to electron and proton transfer, thereby improving the electrochemical reaction rate and ionic conductivity, and further improving the energy efficiency of the battery and reducing the voltage loss.

[0040] The metal porphyrin used as the catalyst in the above electrolyte has a macrocyclic conjugated structure. The complex formed by the macrocyclic conjugated structure and the iron, cobalt, manganese or nickel metal ion not only enables homogeneous catalysis, but also effectively reduces the electrochemical reaction energy barrier between the ferrocyanide ion and the ferricyanide ion, making the conversion between the ferrocyanide ion and the ferricyanide ion faster and more efficient. The 4-carboxyphenyl, 4-sulfonic acid phenyl, 4-aminophenyl and 4-phosphite on the above metal porphyrin not only have hydrophilicity but also reduce the electrode surface energy, improve the wettability of the electrolyte to the electrode, so that the electrolyte can also be uniformly distributed at the electrode interface, promoting homogeneous catalysis. The main role of the base in the above electrolyte is to provide an ion conduction medium, maintain the ion balance inside the battery, and ensure the normal operation of the battery; under alkaline conditions, the iron ion in the ferrocyanide salt undergoes a redox reaction to realize the charging and discharging process of the battery, and the metal porphyrin is uniformly distributed in the electrolyte, reducing the concentration gradient, so that the redox reaction occurs in a more uniform environment. The interaction of ferrocyanide salt, base and metal porphyrin synergistically improves the energy efficiency and voltage efficiency of the battery and reduces the voltage loss of the battery.

[0041] The catalyst in the above electrolyte does not need to be loaded on the positive electrode or the negative electrode, avoiding the problem of catalyst failure caused by falling off and loss of the supported catalyst during long-term cycling.

[0042] The zinc-iron flow battery prepared by using the above electrolyte as the positive electrode electrolyte not only has high energy efficiency and low voltage loss, but also has the advantages of high energy density, long cycle life, low electrolyte cost and safety and environmental protection.

[0043] In some embodiments, the catalyst comprises at least one of tetra(4-carboxyphenyl) porphyrin iron (III), tetra(4-carboxyphenyl) porphyrin cobalt (II), tetra(4-carboxyphenyl) porphyrin manganese (II), tetra(4-carboxyphenyl) porphyrin nickel (II), tetra(4-sulfonatophenyl) porphyrin iron (III), tetra(4-sulfonatophenyl) porphyrin cobalt (II), tetra(4-sulfonatophenyl) porphyrin manganese (II), tetra(4-sulfonatophenyl) porphyrin nickel (II), tetra(4-aminophenyl) porphyrin iron (III), tetra(4-aminophenyl) porphyrin cobalt (II), tetra(4-aminophenyl) porphyrin manganese (II), tetra(4-aminophenyl) porphyrin nickel (II), tetra(4-phosphonato) porphyrin iron (III), tetra(4-phosphonato) porphyrin cobalt (II), tetra(4-phosphonato) porphyrin manganese (II), and tetra(4-phosphonato) porphyrin nickel (II).

[0044] In some embodiments, the catalyst comprises at least one of tetra(4-sulfonatophenyl) porphyrin manganese (II), tetra(4-phosphonato) porphyrin iron (III), tetra(4-carboxyphenyl) porphyrin cobalt (II), and tetra(4-aminophenyl) porphyrin nickel (II). The use of this catalyst further improves the energy efficiency of the battery and further reduces the voltage loss.

[0045] In some embodiments, the catalyst comprises at least one of tetra(4-sulfonatophenyl) porphyrin manganese (II), tetra(4-phosphonato) porphyrin iron (III), tetra(4-carboxyphenyl) porphyrin cobalt (II), and tetra(4-aminophenyl) porphyrin nickel (II). The use of this catalyst further improves the energy efficiency of the battery and further reduces the voltage loss.

[0046] In some embodiments, the molar concentration ratio of the catalyst to the ferrocyanide ions in the ferrocyanide salt is 0.01% to 0.1%. At this concentration ratio, the electrochemical reaction barrier is lower and the positive electrode reaction rate is higher, and the positive electrode surface active sites are not overcrowded, reducing concentration polarization and further promoting the homogeneous catalysis of the catalyst, thereby improving the voltage efficiency and energy efficiency of the battery and reducing the voltage loss.

[0047] For example, the molar concentration ratio of the catalyst to the ferrocyanide ions in the ferrocyanide salt is 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, or a range formed by any two of the above values as end values. The molar concentration ratio of the catalyst to the ferrocyanide ions in the ferrocyanide salt is preferably 0.02% to 0.06%. The molar concentration ratio of the catalyst to the ferrocyanide ions in the ferrocyanide salt is more preferably 0.02% to 0.05%.

[0048] In some embodiments, the concentration of ferrocyanide ions in the electrolyte is 0.2 mol / L to 1.60 mol / L. The concentration of ferrocyanide ions in this range is conducive to maintaining the ion concentration balance in the positive electrolyte, so that the ion migration is maintained at the optimal rate, which not only maintains the reaction activity of the positive electrode of the battery, but also avoids concentration polarization, promotes homogeneous catalysis of the catalyst, and thus improves the electrical performance of the battery.

[0049] For example, the concentration of ferrocyanide ions in the electrolyte is 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, 0.9 mol / L, 1.0 mol / L, 1.1 mol / L, 1.2 mol / L, 1.3 mol / L, 1.4 mol / L, 1.5 mol / L, and 1.60 mol / L. The concentration of ferrocyanide ions in the electrolyte is preferably 0.2 mol / L to 1.0 mol / L. The concentration of ferrocyanide ions in the electrolyte is more preferably 0.4 mol / L to 1.0 mol / L.

[0050] In some embodiments, the concentration of the base is 1.0 mol / L to 6.0 mol / L.

[0051] For example, the concentration of the base is 1.0 mol / L, 2.0 mol / L, 3.0 mol / L, 4.0 mol / L, 5.0 mol / L, and 6.0 mol / L. The concentration of the base is preferably 2 mol / L to 4 mol / L.

[0052] In some embodiments, the ferrocyanide salt includes at least one of sodium ferrocyanide and potassium ferrocyanide.

[0053] In some embodiments, the base includes at least one of sodium hydroxide, potassium hydroxide, and lithium hydroxide, preferably at least one of sodium hydroxide and potassium hydroxide.

[0054] In some embodiments, the components of the electrolyte include sodium ferrocyanide, potassium hydroxide, manganese (II) tetra(4-sulfonatophenyl) porphyrin, and water.

[0055] In some embodiments, the components of the electrolyte include potassium ferrocyanide, sodium hydroxide, iron (III) tetra(4-phosphonato) porphyrin, and water.

[0056] In a second aspect of the present application, a method for preparing an electrolyte is provided, which comprises mixing the base, the ferrocyanide salt, and the catalyst in water to obtain the electrolyte.

[0057] In some embodiments, the mixing of the base, the ferrocyanide salt and the catalyst in water comprises the steps of:

[0058] The base is first dissolved in water to obtain a base solution;

[0059] The ferrocyanide salt and the catalyst are then mixed in the base solution to obtain the electrolyte.

[0060] In a third aspect, the present application provides a zinc-iron flow battery, comprising a positive electrolyte, wherein the positive electrolyte is prepared by the method according to the second aspect or is the electrolyte according to the first aspect.

[0061] It is understood that the zinc-iron flow battery comprises a positive electrolyte, a negative electrolyte, a positive electrode, a negative electrode and a separator, wherein the separator is arranged between the positive electrode and the negative electrode.

[0062] The positive active ion of the zinc-iron flow battery is ferrocyanide, and the redox reaction of ferrocyanide is the main electrochemical reaction of the positive electrode of the zinc-iron flow battery, and the charging and discharging of the battery is realized through this process; the negative active ion of the zinc-iron flow battery is zincate.

[0063] In some embodiments, the preparation method of the negative electrolyte of the zinc-iron flow battery comprises the following steps: first, the base and zinc oxide are placed in a beaker, 200 mL of pure water is added, and the beaker is heated in a water bath at 60 ℃ and stirred; after the zinc oxide is completely dissolved, 600 mL of pure water is slowly added, and the stirring is continued until the electrolyte is clear and transparent; the heating is stopped, and the electrolyte is cooled to room temperature and then used after constant volume.

[0064] In some embodiments, 300 mL of the positive electrolyte and 300 mL of the negative electrolyte are respectively placed in a liquid storage tank to form a battery system with a single cell having an active area of 48 cm 2 .

[0065] In some embodiments, the positive electrode of the zinc-iron flow battery is made of carbon materials such as carbon felt, graphite felt or carbon cloth.

[0066] In some embodiments, the negative electrode of the zinc-iron flow battery is made of carbon materials such as carbon felt, graphite felt or carbon cloth.

[0067] In some embodiments, the separator of the zinc-iron flow battery is a perfluorosulfonic acid proton exchange membrane.

[0068] In a fourth aspect, the present application provides a power utilization device, comprising the zinc-iron flow battery according to the third aspect.

[0069] The electric device includes, but is not limited to, an electric vehicle, an electric ship and an emergency power supply.

[0070] In a fifth aspect of the present application, a power storage device is provided, which comprises the zinc-iron flow battery according to the third aspect.

[0071] The power storage device includes, but is not limited to, a solar power generation system, a wind power generation system, a power grid energy storage system and an uninterruptible power supply system.

[0072] The following is a specific embodiment.

[0073] Embodiment 1

[0074] A zinc-iron flow battery:

[0075] Preparation of the negative electrolyte: 3.0 mol of sodium hydroxide (purity 95%) and 0.2 mol of zinc oxide (purity 99%) were weighed into a beaker, 200 mL of pure water was added, and the solution was heated and stirred in a water bath at 60°C. After the zinc oxide was completely dissolved, 600 mL of pure water was slowly added, and the stirring was continued until the electrolyte was clear and transparent. The heating was stopped, and the solution was cooled to room temperature for constant volume. The prepared electrolyte had a zincate concentration of 0.2 mol / L.

[0076] Preparation of the positive electrolyte: 3.0 mol of sodium hydroxide was weighed into a beaker, 400 mL of pure water was added, and the solution was heated and stirred in a water bath at 50°C. After the sodium hydroxide was completely dissolved, 300 mL of pure water was added, and 0.4 mol of potassium ferrocyanide (purity 99%) was added. After the solution was clear and transparent, 0.4×10 -3 mol of tetra(4-phosphinic acid) porphyrin iron (III) was added, which was 0.1% of the molar amount of sodium ferrocyanide. After the catalyst was completely dissolved, the solution was cooled to room temperature for constant volume. The prepared electrolyte had a ferrocyanide concentration of 0.4 mol / L. Tetra(4-phosphinic acid) porphyrin iron (III) was commercially available (Xi'an Qiyue Biological Technology Co., Ltd.).

[0077] 300 mL of the above positive electrolyte and 300 mL of the negative electrolyte were taken into a storage tank, respectively, to form a single cell with an active area of 48 cm 2 . The single cell was assembled by connecting the inlet and outlet joints, end plates, hard graphite bipolar plates, electrode frames, gaskets, carbon felt electrodes, perfluorosulfonic acid proton exchange membranes, bolts and nuts. Both the positive and negative electrodes used carbon felt electrodes.

[0078] Embodiment 2

[0079] A zinc-iron flow battery:

[0080] Negative electrolyte preparation: potassium hydroxide (purity 95%) 3.0 mol, zinc oxide (purity 99%) 0.2 mol were weighed in a beaker, 200 mL of pure water was added, heated in a water bath at 60°C and stirred, after the zinc oxide was completely dissolved, 600 mL of pure water was slowly added, and the electrolyte was continuously stirred until it was clear and transparent, the heating was stopped, and the electrolyte was cooled to room temperature and then diluted to volume. The concentration of zincate in the electrolyte was 0.2 mol / L.

[0081] Positive electrolyte preparation: potassium hydroxide 3.0 mol was weighed in a beaker, 300 mL of pure water was added, heated in a water bath at 50°C and stirred, after the potassium hydroxide was completely dissolved, 400 mL of pure water was added, and 0.4 mol of sodium ferrocyanide (purity 99%) was added, the solution was clear and transparent, and then 0.2×10 -3 mol of manganese (II) tetra (4-sulfonatophenyl) porphyrin catalyst, which was 0.05% of the molar amount of sodium ferrocyanide, was added. After the catalyst was completely dissolved, the electrolyte was cooled to room temperature and diluted to volume. The concentration of ferrocyanide in the electrolyte was 0.4 mol / L. The manganese (II) tetra (4-sulfonatophenyl) porphyrin was a commercially available product.

[0082] 300 mL of the above positive electrolyte and negative electrolyte were taken into the liquid storage tank respectively, and a single cell with an active area of 48 cm 2 was used to form a battery system.

[0083] Example 3

[0084] Example 3 is basically the same as Example 1, except that in the positive electrolyte, an equimolar amount of cobalt (II) tetra (4-carboxyphenyl) porphyrin is used instead of iron (III) tetra (4-phosphonate) porphyrin.

[0085] Example 4

[0086] Example 4 is basically the same as Example 1, except that in the positive electrolyte, an equimolar amount of nickel (II) tetra (4-aminophenyl) porphyrin is used instead of iron (III) tetra (4-phosphonate) porphyrin.

[0087] Example 5

[0088] Example 5 is basically the same as Example 1, except that in the positive electrolyte, the amount of catalyst iron (III) tetra (4-phosphonate) porphyrin added is 0.04% of the molar amount of sodium ferrocyanide.

[0089] Example 6

[0090] Example 6 is basically the same as Example 1, except that in the positive electrolyte, the concentration of ferrocyanide is 1.6 mol / L.

[0091] Comparative Example 1

[0092] A zinc-iron flow battery:

[0093] Preparation of the negative electrolyte: 3.0 mol of potassium hydroxide (purity 95%) and 0.2 mol of zinc oxide (purity 99%) were weighed into a beaker, 200 mL of pure water was added, and the mixture was heated in a water bath at 60°C and stirred. After the zinc oxide was completely dissolved, 600 mL of pure water was slowly added, and the stirring was continued until the electrolyte was clear and transparent. The heating was stopped, and the mixture was cooled to room temperature. The volume was then adjusted to obtain an electrolyte with a zincate concentration of 0.2 mol / L.

[0094] Preparation of the positive electrolyte: 3.0 mol of potassium hydroxide was weighed into a beaker, 300 mL of pure water was added, and the mixture was heated in a water bath at 50°C and stirred. After the potassium hydroxide was completely dissolved, 400 mL of pure water was added, and 0.4 mol of sodium ferrocyanide (purity 99%) was added. The solution was clear and transparent, and then cooled to room temperature. The volume was adjusted to obtain an electrolyte with a ferrocyanide concentration of 0.4 mol / L.

[0095] 300 mL of the above positive electrolyte and 300 mL of the above negative electrolyte were taken into a storage tank, respectively, and a single cell with an active area of 48 cm 2 was used to form a battery system.

[0096] Comparative Example 2

[0097] Comparative Example 2 was basically the same as Example 1, except that in the positive electrolyte, an equimolar amount of tetraphenylporphyrin was used to replace the tetra(4-phosphinic acid) porphyrin iron (III), and the structural formula of the tetraphenylporphyrin was as follows:

[0098]

[0099] wherein R is a phenyl group.

[0100] The catalysts in the positive electrolyte in the above examples and comparative examples can be commercially available products.

[0101] The battery systems prepared in Examples 1-6 and Comparative Examples 1-2 were tested for energy efficiency and voltage efficiency, and the test results are shown in Table 1 below.

[0102] The test conditions or test standards for each performance test item are as follows:

[0103] Constant current charge and discharge tests were carried out at a current density of 80 mA / cm 2 , the charging time was 30 min, the protection voltage was set to 2.2 V, and the discharge was set to 0.5 V voltage cutoff.

[0104] The energy efficiency is the ratio of the discharge energy to the charging energy; the voltage efficiency is the ratio of the average discharge voltage to the average charging voltage.

[0105] Table 1

[0106]

[0107] From the above Table 1, it can be seen that, in combination Figure 1 , Comparative Example 1 completed 80 times of charge-discharge tests, the voltage efficiency was 80.72%, and the energy efficiency was 80.26%; in combination Figure 2 , Example 1 completed 120 times of charge-discharge tests, the coulombic efficiency was 98.06%, the voltage efficiency was 90.86%, and the energy efficiency was 89.10%; the voltage efficiency and the energy efficiency of Example 1 were respectively increased by about 10.14% and 8.84% than Comparative Example 1; in combination Figure 3 , the charge termination voltage of Comparative Example 1 was 2.03V; in combination Figure 4 , the charge termination voltage of Example 1 was 1.75V, which was decreased by 0.28V than Comparative Example 1.

[0108] Comparative Example 2 completed 80 times of charge-discharge tests, the voltage efficiency was 75.23%, and the energy efficiency was 72.3%, and there was still a problem of large voltage loss and low energy efficiency.

[0109] Example 2 completed 120 times of charge-discharge tests, the coulombic efficiency was 97.04%, the voltage efficiency was 88.52%, and the energy efficiency was 85.9%, the voltage efficiency and the energy efficiency were respectively increased by about 7.8% and 5.64% than Comparative Example 1, the charge termination voltage was 1.83V, which was decreased by 0.2V than Comparative Example 1.

[0110] The zinc-iron flow batteries prepared by using the positive electrolyte including ferrocyanide salt, base, metal porphyrin catalyst and water in Examples 1-6 all have high energy efficiency, voltage efficiency and coulombic efficiency.

[0111] In addition, by comparing Comparative Example 1 with Example 5, it can be seen that, in the above positive electrolyte, when the molar concentration ratio of the catalyst to the ferrocyanide ion in the ferrocyanide salt is 0.02%-0.06%, the zinc-iron flow battery has higher energy efficiency and voltage efficiency and smaller voltage loss. By comparing Comparative Example 1 with Example 6, it can be seen that, in the above positive electrolyte, when the concentration of the ferrocyanide ion is 0.2 mol / L-1.0 mol / L, the zinc-iron flow battery has higher energy efficiency and voltage efficiency and smaller voltage loss.

[0112] The technical features of the above-described examples can be combined arbitrarily, and in order to make the description simple, all possible combinations of the technical features in the above-described examples are not described, however, as long as the combinations of the technical features do not exist contradictory, it should be considered that it is within the scope of the present disclosure.

[0113] The above embodiments only express several implementation manners of the present application, and the description is more specific and detailed, but it should not be understood as a limitation on the scope of the patent. It should be noted that for ordinary skilled persons in the art, without departing from the concept of the present application, several modifications and improvements can be made, which are within the scope of protection of the present application. Therefore, the protection scope of the patent of the present application should be subject to the appended claims.

Claims

1. A zinc-iron flow battery positive electrolyte, characterized in that, The components of the electrolyte include ferrocyanide, base, catalyst and water; the catalyst includes a compound with the following structural formula: wherein R is 4-carboxyphenyl, 4-sulfonic acid phenyl, 4-aminophenyl or 4-phosphorous acid, four R on the same catalyst are the same or different; M is iron (III), cobalt (II), manganese (II) or nickel (II); The concentration of ferrocyanide ions in the electrolyte is 0.2 mol / L to 1.60 mol / L.

2. The zinc-iron flow battery positive electrolyte of claim 1, wherein, The catalyst includes at least one of tetra(4-sulfonic acid phenyl) porphyrin manganese (II), tetra(4-phosphorous acid) porphyrin iron (III), tetra(4-carboxyphenyl) porphyrin cobalt (II) and tetra(4-aminophenyl) porphyrin nickel (II).

3. The zinc-iron flow battery positive electrolyte of claim 1, wherein, The molar concentration ratio of the catalyst to the ferrocyanide ions in the ferrocyanide is 0.01% to 0.1%.

4. The zinc-iron flow battery positive electrolyte of claim 1, wherein, The concentration of ferrocyanide ions in the electrolyte is 0.2 mol / L to 1.0 mol / L.

5. The zinc-iron liquid flow battery positive electrolyte of any one of claims 1 to 4, wherein, The concentration of the base is 1.0 mol / L to 6.0 mol / L.

6. The zinc-iron liquid flow battery positive electrolyte of any one of claims 1 to 4, wherein, The ferrocyanide includes at least one of sodium ferrocyanide and potassium ferrocyanide.

7. The zinc-iron liquid flow battery positive electrolyte of any one of claims 1 to 4, wherein, The base includes at least one of sodium hydroxide, potassium hydroxide and lithium hydroxide.

8. The zinc-iron liquid flow battery positive electrolyte of any one of claims 1 to 4, wherein, At least one of the following conditions is met: (1) the components of the electrolyte include sodium ferrocyanide, potassium hydroxide, tetra(4-sulfonic acid phenyl) porphyrin manganese (II) and water; (2) the components of the electrolyte include potassium ferrocyanide, sodium hydroxide, tetra(4-phosphorous acid) porphyrin iron (III) and water.

9. The method of making a zinc-iron flow battery positive electrolyte according to any one of claims 1 to 8, wherein, The base, the ferrocyanide and the catalyst are mixed in water to prepare the electrolyte.

10. The method of claim 9, wherein the zinc-iron flow battery positive electrolyte is prepared by the steps of: The mixing of the base, the ferrocyanide and the catalyst in water includes the following steps: First, the base is dissolved in water to prepare a base solution; Then, the ferrocyanide and the catalyst are mixed in the base solution to prepare the electrolyte.

11. A zinc-iron flow battery, characterized in that, The zinc-iron flow battery positive electrolyte prepared by the preparation method of any one of claims 9 to 10.

12. An electrical device, comprising: The zinc-iron flow battery of claim 11.

13. An energy storage device, characterized by, The zinc-iron flow battery of claim 11.

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