WO2020035037A1 - 液流电池电解液的制备方法 - Google Patents

液流电池电解液的制备方法 Download PDF

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Publication number
WO2020035037A1
WO2020035037A1 PCT/CN2019/100830 CN2019100830W WO2020035037A1 WO 2020035037 A1 WO2020035037 A1 WO 2020035037A1 CN 2019100830 W CN2019100830 W CN 2019100830W WO 2020035037 A1 WO2020035037 A1 WO 2020035037A1
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vanadium
electrolyte
vanadium oxide
hydrochloric acid
present
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PCT/CN2019/100830
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English (en)
French (fr)
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祖革
王瑾
郑晓昊
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江苏泛宇能源有限公司
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/18—Regenerative fuel cells, e.g. redox flow batteries or secondary fuel cells
    • H01M8/184—Regeneration by electrochemical means
    • H01M8/188—Regeneration by electrochemical means by recharging of redox couples containing fluids; Redox flow type batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/18—Regenerative fuel cells, e.g. redox flow batteries or secondary fuel cells
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/30—Hydrogen technology
    • Y02E60/50—Fuel cells

Definitions

  • the invention belongs to the field of production of flow batteries, in particular to a method for preparing an electrolyte for an all-vanadium flow battery.
  • Flow battery technology has the natural advantages of large-scale energy storage: the amount of stored electricity is linearly proportional to the volume of the electrolyte, and the charge and discharge power is determined by the size and number of the stack, so different designs from kW to MW can be designed according to demand. Charging and discharging power, continuous flow batteries with different energy storage volume for 1 hour to several days. Based on commonly used inorganic acids and electrolytes, the chemical composition of the electrolyte is stable, easy to store, has a small impact on the environment, and has a very low self-discharge coefficient, making it suitable for long-term storage of electrical energy.
  • the reaction temperature of the battery is normal temperature and pressure.
  • the electrolyte flow process is a natural water-based circulation heat dissipation system with extremely high safety performance.
  • the impact of the accident is much lower than other large energy storage solutions. Due to its stable and reliable charge-discharge cycle, there is no upper limit for the theoretical charge-discharge times.
  • the electrolyte In flow batteries, the electrolyte is an important part of electrical energy storage, and its stability and life directly determine the capacity of the entire battery system. At present, most of the products of flow battery companies in the world are still in the demonstration projects for grid-level energy storage, far from meeting the requirements for reliability and stability of commercial products. Most battery systems that have reached the scale of demonstration projects use pure sulfuric acid-based electrolytes containing vanadium ions, and a few use sulfuric acid / hydrochloride-based mixed electrolytes containing vanadium ions.
  • the preparation of the electrolyte usually uses high-priced vanadium oxide as the starting material.
  • a diluted acid solution is added with a reducing agent or a low-priced vanadium oxide.
  • Highly priced vanadium ions eventually reduce to an equilibrium electrolyte.
  • the acidic solution the traditional solution is sulfuric acid.
  • hydrochloric acid is used as the acidic solution.
  • Cited Document 1 discloses a method for preparing an electrolyte for a flow battery using a hydrochloric acid solution, which uses V 2 O 5 and V 2 O 3 as starting materials, and uses hydrochloric acid as an acidic solution under the action of a reducing agent or an oxidant. To obtain vanadium ions in various valence states and form the required electrolyte for flow batteries.
  • Citation 2 discloses a system and method for preparing a highly active all-vanadium flow battery with a specific valence electrolyte. After the vanadium-containing material is accurately controlled by fluidization, it is reduced to a low-priced vanadium oxide with an average valence of any value in the range of 3.0 to 4.5. It is dissolved by adding water and sulfuric acid, and further activated by microwave fields to obtain a specific valence vanadium electrolysis liquid.
  • Reference 3 discloses a system and method for producing a 3.5-valent high-purity vanadium electrolyte.
  • High-purity vanadium trichloride is hydrolyzed to vanadium pentoxide by gas-phase hydrolysis in a fluidized bed.
  • the vanadium pentoxide is precisely controlled and reduced to a low-priced vanadium oxide with an average valence of 3.5 in a reducing fluidized bed.
  • a 3.5-valent high-purity vanadium electrolyte can be obtained by adding water and sulfuric acid solution at low temperature under an external microwave field, which can be directly used in a new stack of vanadium flow battery.
  • the special chemical effect of microwave field promotes the dissolution of vanadium oxide and activates vanadium ions.
  • the electrolyte is prepared by dissolving in the low temperature range, which greatly improves the electrolyte activity.
  • reference 4 discloses a system and method for preparing a high-purity electrolytic solution of a vanadium battery, which uses vanadium trichloride as a raw material to prepare vanadium with an average vanadium state of 3.5 by liquid-phase hydrolysis and fluidized reduction.
  • Low-priced vanadium oxide, dissolved with clean water and sulfuric acid, and further activated by ultraviolet rays to obtain a vanadium electrolyte, can be directly used in a new stack of vanadium flow batteries.
  • Citation 5 provides a system and method for preparing a highly active, high-purity specific valence vanadium electrolyte.
  • industrial vanadium oxide is converted into vanadium trichloride, and crude vanadium trichloride is obtained through dust removal and leaching; high-purity low-price vanadium oxide is obtained through rectification, catalytic oxidation, and precise control reduction.
  • the average valence of vanadium can be any value within 3.0 ⁇ 4.0; under the action of the activation device, pure water and pure sulfuric acid solution can be added to dissolve at low temperature to obtain a high-activity and high-purity specific valence vanadium electrolyte, which can be directly used in all vanadium liquids. Stream battery.
  • Citation 6 discloses a method for preparing an electrolyte for an all-vanadium flow battery.
  • the V 2 O 5 powder is reduced in hydrogen to prepare a V 2 O 4 powder and a V 2 O 3 powder.
  • the obtained V 2 O 4 and V 2 O 3 were respectively dissolved using a sulfuric acid solution to obtain an electrolyte solution for an all-vanadium flow battery.
  • Citation 1 uses high-priced alum pentoxide as a starting material to react with hydrochloric acid. Since high-priced vanadium ions have strong oxidizing properties, it is easy to cause oxidation of chloride ions and generate toxic chlorine gas. In addition, when using alum pentoxide or vanadium trioxide to form the electrolyte of the positive electrode or the negative electrode, an additional reducing agent or oxidant is required and complex adjustment can be performed to obtain an electrode liquid for a balanced flow battery. Therefore, The preparation process cannot be said to be simple.
  • the preparation process of the above-mentioned electrolytic solution cannot be said to be simple, and there is still room for further improvement in improving the corrosiveness and the long life of the flow battery by obtaining a sulfuric acid-based electrolytic solution using sulfuric acid as an acidic solution.
  • the present invention provides a method for preparing an electrolyte for an all-vanadium flow battery.
  • the method uses a vanadium oxide composed of the following general formula (1) as a direct starting material, and hydrochloric acid. It is an acidic solution, and an electrolytic solution is prepared in the presence of an activated catalyst.
  • V valence state of V
  • x: y 1: (1.6 to 1.85).
  • the above method of the present invention does not have high requirements for the purity of raw materials, and has stronger applicability of raw materials.
  • Using the oxide of the general formula (1) as a raw material can directly obtain the required electrolytic solution, without the need to mix additional oxidants or reducing agents.
  • the activation catalyst present in the electrolytic solution can complete the activation of the electrolytic solution in the process of forming the electrolytic solution without a separate activation process.
  • the present invention uses hydrochloric acid as an acidic solution, which is beneficial to further improve the performance of the electrolyte compared to the sulfuric acid-based electrolyte, avoids damage to the flow battery components, and improves the service life.
  • the present invention first provides a method for preparing an electrolyte for a flow battery, and the method includes the following steps:
  • V valence state of V
  • x: y 1: (1.6 to 1.85);
  • the electrolyte further includes one or more ions selected from Mo, Mn, Pb, and Bi.
  • the average valence state of V is +3.3 to +3.5.
  • the concentration of the hydrochloric acid solution is 10 to 38% by mass.
  • the method further includes the following steps:
  • the step of performing a reduction reaction of a highly oxidized vanadium oxide to obtain the vanadium oxide of the general formula (1) is performed.
  • the highly oxidized vanadium oxide includes V 2 O 5 .
  • the reduction reaction of the vanadium oxide with a high oxidation value is performed in the presence of a reducing gas, preferably, the reducing gas is H 2 , One or any combination of CO, hydrogen sulfide, methane, sulfur dioxide, ethylene or NH 3 .
  • the present invention also provides a method for preparing a flow battery, which includes a method for preparing an electrolyte according to any one of the above.
  • the method for preparing an electrolytic solution of the present invention has the following effects:
  • the method of the present invention does not need to use high-valent vanadium oxide as a raw material to directly react with hydrochloric acid, reducing the possibility of oxidizing chlorine ions to chlorine gas;
  • hydrochloric acid is used as the acidic solution to prepare the electrolyte, which can avoid damage to the stack components during the use of the flow battery, and is beneficial to the extension of the service life.
  • the electrolyte requires acidity. In battery operation, once the electrolyte acidity deviates, it should be adjusted back to the specified range as soon as possible.
  • HCl gas is used to supplement the acidity without changing the electrolyte volume.
  • the volume of the electrolyte will be changed because it is supplemented with a liquid, and there are limitations when the size of the electrolyte tank is fixed.
  • the preparation method of the electrolytic solution of the present invention does not need a separate electrolytic solution activation process, and can complete the activation of the electrolytic solution while preparing the electrolytic solution.
  • an activation catalyst is used in the pure hydrochloric acid-based electrolytic solution of the present invention, the battery performance is improved. More obvious.
  • an electrolytic solution of a balanced or unbalanced flow battery can be directly produced according to the average composition of x and y in V x O y ;
  • the preparation process of the electrolytic solution of the present invention is relatively simple, and the industry has a significant improvement in improving the preparation efficiency and performance of the electrolytic solution.
  • Figure 1 Flow chart of preparation of the electrolyte of the present invention
  • Figure 3 Comparison of corrosion of bipolar plate materials by different electrolytes under the conditions of Figure 2
  • a method for preparing an electrolyte for an all-vanadium flow battery is provided.
  • the vanadium oxide that directly reacts with an acidic solution is referred to as a "direct raw material” or “starting raw material”, and at the same time, the industrial raw material or mineral raw material that obtains these "direct raw materials” or “starting raw materials” It is "original raw material” or “original source”.
  • a vanadium oxide composed of the following general formula (1) is used as a direct raw material for preparing an electrolyte for an all-vanadium battery:
  • V valence state of V
  • x: y 1: (1.6 to 1.85);
  • the process for industrially obtaining an oxide of the general formula (1) or the original source of the oxide is not particularly limited in the present invention, and can be obtained in a conventional manner, for example, reducing a vanadium oxide in a high valence state.
  • the raw material of the vanadium oxide with a high oxidation state which can be obtained by various methods known in the art, for example, by leaching a vanadium solution or a vanadium-rich material (such as industrial-grade ammonium polyvanadate, The vanadium solution obtained by dissolving ammonium metavanadate, industrial grade vanadium pentoxide, etc.) is used as a raw material, and is purified by chemical precipitation purification or (and) solvent extraction / ion resin exchange to obtain a pure vanadium solution and then ammonium salt precipitation.
  • a vanadium solution or a vanadium-rich material such as industrial-grade ammonium polyvanadate, The vanadium solution obtained by dissolving ammonium metavanadate, industrial grade vanadium pentoxide, etc.
  • the pure ammonium polyvanadate or ammonium metavanadate is obtained, or it is calcined and decomposed to obtain high-purity vanadium pentoxide powder.
  • a method for preparing high-purity vanadium pentoxide using vanadium-titanium magnetite, vanadium slag, and a vanadium-containing substance as a raw material by using a chlorination method is used.
  • the obtained high-valence vanadium oxide is reduced, for example, a reducing agent may be used to directly reduce the oxide of V 2 O 5 , or, in other industrial production, other + 5-valent vanadium may be used.
  • the compound is mixed and dissolved with an acidic solution, a reduction reaction is performed in the presence of a reducing agent, and then a precipitate is obtained by adding an alkaline substance, and then a low-value oxide is obtained by washing and drying.
  • the reduction method used in the above process is not particularly limited, and for example, a general reducing compound such as a reducing acid, a reducing alcohol, an aldehyde compound, typically, such as oxalic acid, etc .; or a reducing gas, etc., typically, For example, one or any combination of H 2 , CO, hydrogen sulfide, methane, sulfur dioxide, ethylene or NH 3 .
  • an oxide of the general formula (1) is used as a direct raw material for preparing an electrolytic solution
  • V 2 O 5 is used as a direct raw material in the preparation of an electrolytic solution for an all-vanadium flow battery in the prior art or with Vanadium oxides with a valence of 3.0 to 4.0 are different as direct raw materials (often, these direct raw materials are required to have a higher purity.
  • vanadium with a valence of 3.0 to 4.0 The oxide is also obtained based on the reduction of V 2 O 5 with high purity as the raw material.
  • the present invention does not have the purer restrictions or requirements for the purity of oxides having the composition of the general formula (1).
  • the purity of the vanadium oxide having an average valence of +3.2 to +3.7 may be 90% by mass or more. In some preferred embodiments, the purity of the above oxide is 95% by mass or more, and in other preferred embodiments, the purity of the above oxide is 98% by mass or more.
  • the main factors affecting the purity of the above vanadium oxides come from the presence of other metal ions or their oxides, such as Fe, Na, K, Ca ions or oxides, or noble metal ions or oxides such as Au, Ag, or Pt.
  • other metal ions or their oxides such as Fe, Na, K, Ca ions or oxides, or noble metal ions or oxides such as Au, Ag, or Pt.
  • the presence of these impurities has little effect on the performance of the electrolyte. Can allow the presence of these impurities in a certain range without removal.
  • the content of the impurities contained in the vanadium oxide of the general formula (1) is 100 ppm or less, It is preferably 50 ppm or less, and more preferably 30 ppm or less.
  • the average valence state of vanadium is preferably +3.3 to +3.6. In other preferred embodiments, the vanadium's The average valence state is preferably +3.3 to +3.5, and more preferably +3.4 to +3.5.
  • these vanadium oxides are low-priced vanadium, such as +3 and below valence vanadium and +4 and above valence vanadium. Mixed oxide system.
  • an oxide of vanadium composed of the general formula (1) is dissolved in an acidic solution to prepare an electrolytic solution.
  • the acidic solution used in the present invention is a hydrochloric acid solution.
  • a hydrochloric acid solution has a concentration of 10% to 38% by mass.
  • such a hydrochloric acid solution has 10% by mass. % To 35% by mass.
  • the use of a hydrochloric acid solution instead of sulfuric acid as an acidic solution considers, on the one hand, that the solubility of vanadium oxide is relatively better, and on the other hand, it is considered that although hydrochloric acid is used as the acidic solution,
  • the valence of vanadium in the oxide is between +3.2 and +3.7, so there is no oxidation of chloride ions due to the high oxidation value of vanadium, which can also avoid the generation of undesired chlorine gas. .
  • hydrochloric acid as an acidic solution and the avoidance of traditional sulfuric acid are due to the advantages of pure hydrochloric acid-based electrolytes compared with sulfuric acid-based electrolytes in terms of the present invention: the formed electrolyte has lower viscosity and better fluidity; The resulting electrolyte is more conductive and helps improve battery efficiency.
  • the vanadium oxide of the general formula (1) and hydrochloric acid are mixed and dissolved.
  • equipment used for mixing there are no special requirements, and mixing equipment commonly used in the art can be used, such as a reaction tank equipped with a feeding port. In some preferred embodiments of the present invention, these devices have a stirring device in addition to a feeding device.
  • the reaction temperature is preferably room temperature or lower, and more preferably 20 ° C or lower.
  • the vanadium oxide is dispersed in a hydrochloric acid solution to dissolve, and the following reaction is performed:
  • VCl 3.5 here is a statistical average value.
  • such a composition can basically be regarded as a mixture of VCl 3 and VOCl 2 in a ratio of 1: 1. Therefore, it can be understood that when V 2 O 3.5 (V average valence state is +3.5) is mixed with hydrochloric acid, an electrolyte solution composed entirely of + 3-valent vanadium ions and + 4-valent vanadium ions is directly obtained, and such an The electrolyte can be referred to as an equilibrium electrolyte.
  • a vanadium oxide having an average valence state of less than +3.5 and more than +3.2 can be used as a raw material to react with hydrochloric acid.
  • an electrolyte solution composed entirely of + 3-valent vanadium ions and + 4-valent vanadium ions was also obtained.
  • + 3-valent vanadium ions The content of is more than the content of +4 valent vanadium ions.
  • it can be called a negative non-equilibrium electrode solution.
  • a vanadium oxide having an average valence state higher than +3.5 and less than +3.7 can be used as a raw material to react with hydrochloric acid.
  • the obtained electrolytic solution is also an electrolytic solution formed entirely of + 3-valent vanadium ions and + 4-valent vanadium ions.
  • + 3-valent vanadium ions Its content is lower than the content of +4 valent vanadium ions.
  • it can be called a forward non-equilibrium electrolyte.
  • the equilibrium electrolyte can be directly used in the presence of catalytically active metal ions described below.
  • a negative non-equilibrium electrolyte can be used.
  • a negative non-equilibrium electrolyte can be used appropriately, or an equilibrium state can be used.
  • the electrolyte and the negative non-equilibrium electrolyte are mixed in a certain ratio.
  • a high-valent vanadium ion may be reduced using an appropriate reducing agent as needed to obtain a balanced electrolyte or a negative non-equilibrium electrolyte.
  • the reduction method it is not limited, and it may be a conventional reduction method in the art, for example, a reducing gas or other reducing compound may be used.
  • the reducing gas include one or any combination of hydrogen, CO, hydrogen sulfide, methane, sulfur dioxide, ethylene or NH 3 ; for other reducing compounds, aldehydes, alcohols, or
  • the reducing organic acid substance for example, oxalic acid or the like can be typically used.
  • a low-priced vanadium oxide, such as V 2 O 3 can also be added to increase the content of the + 3-valent vanadium ion.
  • the average valence state of vanadium in the oxide of the general formula (1) is +3.2 to +3.7 as a direct raw material for preparing the electrolyte solution of the all-vanadium flow battery.
  • the oxidation state of vanadium in the oxide is If it is too high or too low, the use of the formed non-equilibrium electrolyte will cause obvious restrictions, and additional production costs will need to be paid for the subsequent use of such electrolyte.
  • the reaction solution may be diluted according to actual needs.
  • a relatively high concentration hydrochloric acid solution and a large amount of vanadium oxide are usually used.
  • the electrolytic solution thus obtained has a high vanadium ion concentration.
  • such an electrolyte needs to be further diluted before it can be used. Therefore, without limitation, in the method of the present invention, water may be used for dilution in any step of forming the electrolytic solution.
  • the step of diluting is performed after the acidic solution is contacted with the oxide, and more preferably, The step of diluting is performed after the reaction between the acidic solution and the oxide is completed.
  • the water is deionized water or distilled water.
  • an electrolytic solution is prepared by mixing a vanadium oxide having the general formula (1) with an acidic solution in the presence of an activated catalyst.
  • the activated catalyst may be metal ions, which can promote the mutual conversion of +3 valence vanadium and +2 valence vanadium.
  • the metal ion as the activation catalyst may be one or more ions derived from Mo, Mn, Pb, and Bi.
  • the amount of these metal ions is above 0.1 ppm, or above 0.3 ppm, or above 0.5 ppm, or above 0.7 ppm, or above 1.0 ppm, or above 3.0 ppm, or above 10 ppm, or above 30 ppm , Or 50 ppm or more, and may be 800 ppm or less, or 500 ppm or less, or 300 ppm or less, or 100 ppm or less.
  • the adding time of the activated catalyst is not particularly limited.
  • the activated catalyst ion may be added to an acidic solution in advance, and then the acidic solution is oxidized with vanadium composed of the general formula (1). The materials are mixed to obtain an electrolytic solution.
  • the vanadium oxide composed of the general formula (1) and the acidic solution may be mixed first, and then an activating catalyst may be added to obtain an electrolytic solution.
  • the use of the above-mentioned catalytic activator in a pure hydrochloric acid-based electrolyte enables the electrolyte to be used normally without the need for a separate external activation step.
  • the present invention does not require high purity of the vanadium oxide represented by the general formula (1)
  • the present invention does not exclude the use of a high-purity vanadium oxide.
  • the vanadium oxide obtained by the formula (1) having a high purity can be obtained by a method generally used in the art.
  • a high-purity vanadium pentoxide is obtained based on a high-purity vanadyl chloride
  • a high-purity vanadium oxide represented by the general formula (1) is obtained by a reduction method.
  • the electrolytic solution formed by the vanadium oxide as the direct raw material may be further purified after being dissolved in an acidic substance.
  • the purification step it is preferably performed without adding the above-mentioned activated catalyst.
  • the purification step is not particularly limited, and a chemical purification method and a chemical-electrochemical purification method generally used in the art can be used, and typically, an electrolytic method or an ion exchange method is used, for example.
  • a separate activation step may also be used after obtaining an electrolytic solution with or without the above-mentioned activation catalyst.
  • Perform external activation The activation method can be an existing activation method in the prior art. For example, ultraviolet activation, microwave activation, and the like can be used.
  • a second embodiment of the present invention provides a method for preparing a flow battery. Such a method includes the method for preparing an electrolytic solution according to the first embodiment.
  • the current density has a tendency to increase at the same voltage, and the pure sulfuric acid electrolyte has a tendency to damage the battery element more.
  • Electrolyte 4M HCl and 3M H 2 SO 4
  • Bipolar plate graphite bipolar plate
  • the polarization experiment in Reference Example 1 above is used as a simulation experiment under extreme overcharge conditions, which simulates the influence of different electrolyte environments on the corrosion of graphite bipolar plates under partial overcharge conditions inside the stack.
  • the y-axis unit is voltage V and the x-axis unit is current density A / cm 2 .
  • the slope of the fitted straight line is the equivalent resistance of the battery during charge and discharge. It can be seen from FIG. 6 that the equivalent internal resistance of the battery is 1.0735 / -1.0956 Ohm ⁇ cm 2 using the electrolytic solution added with the catalyst.
  • the following table 3 shows the charge and discharge efficiency data of the battery.
  • FIG. 7 is a polarization curve of a flow battery using the prepared catalyst-free electrolyte.
  • the y-axis unit is voltage V and the x-axis unit is current density A / cm 2 .
  • the slope of the fitted straight line is the equivalent resistance of the battery during charge and discharge. It can be seen from FIG. 7 that, for an electrolyte without any catalyst, the equivalent internal resistance of the battery is 2.504 / -2.7811 Ohm ⁇ cm 2 , which is significantly higher than the equivalent internal resistance of the battery in which the catalyst was added in Example 1.
  • the following table 4 shows the charge and discharge efficiency data of the battery. From the comparison of the equivalent resistance, it can be known that the internal resistance of the battery is higher, and the voltage efficiency of the battery is reduced, resulting in a decrease in the overall energy efficiency. Comparing the various battery efficiencies in Table 4 below and the battery efficiencies in Table 1 of Example 1, it can be clearly seen that the addition of a catalyst can greatly improve battery performance.
  • Example 2 Comparative Example 2 (Comparison of performance of pure sulfuric acid-based and pure hydrochloric acid-based electrolytes)
  • Example 2 an electrolytic solution was obtained according to a method similar to that in Example 1. Its composition was V 4+ of 0.75 M, V 3+ of 0.75 M, and 4 M HCl.
  • Comparative Example 2 uses a method known in the prior art, uses alum pentoxide and sulfuric acid to prepare an electrolyte at room temperature (and adds the same activated catalytic ion as in Example 1), and its composition is V 4+ of 0.75M and V 3+ of 0.75M and H 2 SO 4 of 3M.
  • Example 2 and Comparative Example 2 were respectively used to simulate pure hydrochloric acid-based and pure sulfuric acid-based electrolytes and were tested. The test results are shown in the table.
  • Table 5 shows the test conditions of the electrolytic solution of Example 2 and Table 6 shows the test conditions of the electrolytic solution of Comparative Example 2.
  • Example 1 is compared with Comparative Example 1
  • Comparative Example 2 is compared with Reference Example 2. It can be seen that under the same conditions, no matter the hydrochloric acid or sulfuric acid-based electrolyte, the use of the activation catalyst has significantly improved the voltage efficiency and overall energy efficiency, but for the hydrochloric acid-based electrolyte, after using the activation catalyst The effect is even more pronounced. It also shows that the use of active catalyst in hydrochloric acid-based electrolyte is more valuable.
  • the method provided by the present invention can industrially and efficiently prepare an electrolyte for an all-vanadium flow battery and an all-vanadium flow battery.

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Abstract

本发明涉及一种液流电池电解液的制备方法，所述方法包括如下步骤： a.提供如下通式(1)组成的钒的氧化物的步骤： V xO y …….. (1) 其中，V的平均价态为+3.2价～+3.7价； b.将上述通式(1)组成的钒的氧化物溶解于盐酸溶液，待反应完毕，获得盐酸基钒电解液的步骤，所述电解液中还包括选自源自Mo、Mn、Pb、Bi的一种或多种离子。

Description

液流电池电解液的制备方法 技术领域
本发明属于液流电池的生产领域，具体而言，属于一种全钒液流电池电解液的制备方法。
背景技术
液流电池技术有大规模储能的天然优势：储电量的大小与电解液体积成线性正比，充放电功率由电堆尺寸及数量决定，所以能按照需求，设计出从kW到MW级别不同的充放电功率，可持续放电1小时到数天的不同储能体量的液流电池。基于常用无机酸，无机盐的电解液化学成分稳定，储存方便，对环境影响小，自放电系数极低，适合长期的电能储存。电池反应温度为常温常压，电解液流动过程是自然的水基循环散热系统，安全性能极高，事故影响远低于其他大型储能方案。由于其稳定可靠的充放电循环，理论充放电次数没有上限。
在液流电池中，电解液作为电能存储的重要组成部分，其稳定性和寿命直接决定了整个电池系统的容量。目前世界范围里液流电池企业，其产品绝大部分还处在用于电网级储能的示范性项目，远没有达到商业化产品对可靠性和稳定性的要求。已达到示范项目规模的电池系统，绝大多数采用含有钒离子的纯硫酸基电解液，少部分采用含有钒离子的硫酸基/盐酸基混合电解液。
目前的全钒液流电池中，电解液的制备通常以高价的钒的氧化物作为起始原料，通常是在稀释过的酸性溶液中，加入还原剂或是低价的钒的氧化物，使高价的钒离子最终逐步还原为平衡态的电解液。对于酸性溶液，传统的为硫酸的溶液，近些年也见有使用盐酸作为酸性溶液的报道。
引用文献1公开了一种使用盐酸溶液制备液流电池电解液的方法，其分别使用V 2O 5和V 2O 3作为起始原料，使用盐酸作为酸性溶液，在还原剂或者氧化剂的作用下，获得各种价态的钒离子，并形成所需的液流电池用电解液。
引用文献2公开了一种制备高活性全钒液流电池用、具有特定价态电解液的系统及方法。含钒物料经流态化精准控制还原至平均价态为3.0～4.5范围内任一值的低价钒氧化物后，配加水和硫酸溶解，并进一步采用微波场活化得到特定价态的钒电解液。通过含钒物料与还原尾气换热、还原产物与流化氮气换热实现热量高效利用，在还原流化床内设置内构件和不同高度的排料口实现还原产物价态的精准调控，并利用微波场的特殊化学效应活化钒离子，大幅度提高电解液活性。
引用文献3公开了一种生产3.5价高纯钒电解液的系统及方法。采用流化床气相水解将高纯度的三氯氧钒水解为五氧化二钒，在还原流化床中将五氧化二钒精确控制还原为钒平均价态为3.5的低价钒氧化物，在外加微波场下配加水和硫酸溶液低温溶解得到3.5价高纯钒电解液，可直接用于全钒液流电池新电堆。通过微波场的特殊化学效应促进钒氧化物的溶解并活化钒离子，在低温区间溶解制备电解液，大幅度提高电解液活性。
与引用文献3相似，引用文献4公开了一种制备钒电池高纯电解液的系统及方法，以三氯氧钒为原料，通过液相水解、流态化还原制备钒平均价态为3.5的低价钒氧化物，配加洁净水和硫酸溶解，并进一步采用紫外线活化得到钒电解液，可以直接用于全钒液流电池新电堆。
引用文献5提供了一种制备高活性高纯度特定价态钒电解液的系统及方法。采用流态化氯化，将工业级钒氧化物转化为三氯氧钒，通过除尘、淋洗，得到粗三氯氧钒；经过精馏、催化氧化、精确控制还原得到高纯低价钒氧化物，钒平均价态可为3.0～4.0内任一值；在活化装置作用下配加纯水和纯硫酸溶液低温溶解得到高活性高纯度特定价态钒电解液，可直接用于全钒液流电池。
引用文献6公开了一种全钒液流电池电解液的制备方法，将V 2O 5粉末在氢气中还原制备V 2O 4粉末和V 2O 3粉末。然后使用硫酸溶液将得到的V 2O 4和V 2O 3分别溶解以得到全钒液流电池用电解液。
引用文献1使用高价的五氧化二矾作为起始原料与盐酸反应，由于高价的钒离子具有较强的氧化性，因此，容易引起氯离子的氧化而产生有毒的氯 气。并且，使用五氧化二矾或者使用三氧化二钒形成正极或者负极的电解液时需要借助额外的还原剂或者氧化剂，并经过复杂的调整才能够得到平衡态的液流电池用电极液，因此，制备过程并不能说是简便的。
引用文献2得到平均价态为3.0～4.5范围内任一值的低价钒氧化物后，配加水和硫酸溶解，并经后续活化得到电解液。引用文献3～引用文献5均涉及使用高纯度的三氯氧钒作为起始原料以获得高纯度的五氧化二矾，并且配合独立的活化装置以获得最终的电解液。因此，上述电解液的制备过程也不能说是简便的，并且，以硫酸为酸性溶液得到硫酸基的电解液，在提高腐蚀性以及液流电池的长寿命上还有进一步提升的空间。
引用文献6中使用五氧化二矾作为原料进行还原，在氢气中经还原制备V 2O 4粉末，但该过程需要精确控制还原气体的用量，以确保不发生过度还原或者还原不充分。
因此，虽然本领域中尝试了多种制备全钒液流电池电解液的方法，但在制备的便利性以及电解液的使用性能上仍然存在进一步改进的余地。
引用文献
引用文献1：US 2015/0050570 A1
引用文献2：CN106257725B
引用文献3：CN106257728B
引用文献4：CN106257727A
引用文献5：CN107565153A
引用文献6：CN 103401010A
发明内容
发明要解决的问题
针对本领域上述存在的技术问题，本发明提供了一种制备全钒液流电池电解液的方法，所述方法以如下通式(1)组成的钒的氧化物为直接起始原料，以盐酸为酸性溶液、并在活化催化剂的存在下制备得到电解液。
V xO y……..(1)
其中，V的价态为+3.2价～+3.7价，x:y＝1：(1.6～1.85)。
本发明的上述方法对于原料的纯度要求不高，具有更强的原料适用性。使用通式(1)组成的氧化物为原料能够直接得到所需的电解液，而无必须配合额外的氧化剂或者还原剂。此外，电解液中存在的活化催化剂能够在形成电解液的过程中完成对电解液的活化，而无需单独的活化过程。
此外，本发明使用盐酸作为酸性溶液，相对于硫酸基电解液有利于进一步的提高电解液的使用性能，避免对液流电池部件的损伤，并提高使用寿命。
用于解决问题的方案
通过本发明的详细研究和实践，发现使用如下技术方案能够解决上述问题：
本发明首先提供了一种液流电池电解液的制备方法，所述方法包括如下步骤：
a.提供如下通式(1)组成的钒的氧化物的步骤：
V xO y……..(1)
其中，V的价态为+3.2价～+3.7价，x:y＝1：(1.6～1.85)；
b.将上述通式(1)的钒的氧化物溶解于盐酸溶液，待反应完毕，获得盐酸基钒电解液的步骤，
所述电解液中还包括选自源自Mo、Mn、Pb、Bi的一种或多种离子。
根据以上所述的方法，在优选的实施方案中，所述V的平均价态为+3.3～+3.5价。
根据以上所述的方法，在优选的实施方案中，所述盐酸溶液的浓度为10～38质量％。
根据以上所述的方法，在优选的实施方案中，在a步骤前，还包括如下步骤：
将高氧化价的钒的氧化物进行还原反应以得到所述通式(1)组成的钒的氧化物的步骤，优选地，所述高氧化价的钒的氧化物包括V 2O 5。
根据以上所述的方法，在优选的实施方案中，所述将高氧化价的钒的氧 化物进行还原反应是在还原性气体存在下进行的，优选地，所述还原性气体为H 2，CO，硫化氢，甲烷，二氧化硫，乙烯或NH 3中的一种或任意组合。
进一步，本发明还提供了一种液流电池的制备方法，其包括根据以上任一项的电解液的制备方法。
发明的效果
通过以上技术方案的实施，本发明制备电解液的方法具有如下的效果：
相对于使用高价氧化钒与盐酸制备电解液的方法，本发明方法无需使用高价氧化钒作为原料与盐酸直接反应，减少了将氯离子氧化为氯气的可能；
本发明的电解液的制备方法中，对于原料纯度没有纯度上特别的要求，实际生产中适用性强；
本发明中以盐酸作为酸性溶液制备电解液，能够避免在液流电池在使用过程中对于电堆部件的损伤，有利于使用寿命的延长。
另外，电解液对酸度都是有要求的，电池运行中，一旦电解液酸度出现偏差，要尽快调节回到规定的范围内。使用纯盐酸基电解液时，利用HCl气体补充酸度，不会改变电解液体积。使用纯硫酸基或是盐酸/硫酸混合电解液时，由于补充的是液体，因此会改变电解液体积，在电解液罐大小固定的情况下，会有局限性。
本发明电解液的制备方法，无需独立的电解液活化过程，在制备电解液的同时即可完成对电解液的活化，并且本发明中纯盐酸基电解液中使用活化催化剂时，对于电池性能提高更为明显。
本发明的电解液制备方法，根据V xO y中x与y的平均组成可直接生产平衡或者不平衡的液流电池的电解液；
整体上，本发明的电解液制备过程较为简洁，工业上在提高电解液的制备效率和性能方面具有明显的改进。
附图说明
图1：本发明电解液的制备流程图
图2：使用4M的HCl和3M的H 2SO 4作为电解液模拟过充条件下的对比
图3：图2条件下不同电解液对于双极板材料的腐蚀情况对比
图4：3M H 2SO 4电解液对于石墨双极板在不同极化电压下的腐蚀情况
图5：4M HCl电解液对于石墨双极板在不同极化电压下的腐蚀情况
图6：实施例1电解液的极化曲线
图7：比较例1电解液的极化曲线
具体实施方式
以下将对本发明的全钒液流电池用电解液的制备方法进行详细说明。需要说明的是，除非特殊声明，本发明所使用的单位名称均为本领域通用的国际单位名称。此外，本发明以下出现的数值的点值或者数值范围均应当理解为包括了工业上允许的误差。
<第一实施方式>
本发明的第一实施方式中，提供了一种全钒液流电池电解液的制备方法。
直接原料
本发明中将直接与酸性溶液反应的钒的氧化物称之为“直接原料”或者“起始原料”，同时，将获得这些“直接原料”或者“起始原料”的工业原料或者矿物原料称之为“原始原料”或“原始来源”。
本发明中，使用下述通式(1)组成的钒的氧化物作为制备全钒电池电解液的直接原料：
V xO y……..(1)
其中，V的价态为+3.2价～+3.7价，x:y＝1：(1.6～1.85)；
对于工业上获得上述通式(1)组成的氧化物的过程或者该氧化物的原始来源本发明没有特别的限定，可以以常规的方式得到，例如对高价态的钒的氧化物进行还原。
对于高氧化态的钒的氧化物的原始原料的获得，没有特别的限制，可以通过本领域各种已知的方法获得，例如以浸出钒溶液或富钒物料(如工业级多钒酸铵、偏钒酸铵、工业级五氧化二钒等)溶解得到的钒溶液为原料，采 用化学沉淀净化或(和)溶剂萃取/离子树脂交换等方法进行净化，得到纯净的钒溶液然后进行铵盐沉淀得到纯净的多钒酸铵或偏钒酸铵沉淀，或者再经过煅烧分解得到高纯五氧化二钒粉体。或者使用氯化法，以钒钛磁铁矿、钒渣、含钒催化剂等含钒物质为原料制备高纯五氧化二钒的方法。
对于得到的高价态的钒的氧化物进行还原，例如，可使用还原剂对于V 2O 5的氧化物进行直接还原，或者，在另外的一些工业生产中，可以使用其他的+5价钒的化合物与酸性溶液混合溶解，在还原剂的存在下进行还原反应，进而经过碱性物质的加入得到沉淀物，然后经过清洗、干燥得到低价态的氧化物。
对于以上过程所使用的还原方法没有特别的限定，例如可以使用通常的还原性化合物例如还原性酸、还原性醇、醛类化合物，典型地，例如草酸等；或者还原性气体等，典型地，例如H 2，CO，硫化氢，甲烷，二氧化硫，乙烯或NH 3中的一种或任意组合。
如上本发明中，将通式(1)组成的氧化物作为制备电解液使用的直接原料，与现有技术中作为全钒液流电池的电解液制备中以V 2O 5作为直接原料或者以钒的价态在3.0～4.0之间的钒的氧化物作为直接原料不同(往往，要求这些直接原料具有较高的纯度，在一些情况下对于钒的价态在3.0～4.0之间的钒的氧化物，也是基于高纯度的V 2O 5作为原料还原得到)，本发明对于具有通式(1)组成的氧化物纯度并没有以往较纯的限制或要求，在通式(1)的钒的氧化物中，平均价态为+3.2～+3.7的钒的氧化物的纯度在90质量％以上即可。在一些优选的实施方案中，上述氧化物的纯度为95质量％以上，在另外一些优选的实施方案中，上述氧化物的纯度为98质量％以上。
影响以上钒的氧化物纯度的主要因素来自于其他金属离子或其氧化物的存在，例如Fe、Na、K、Ca等离子或氧化物，或者例如Au、Ag或Pt等贵金属离子或氧化物。与纯硫酸基电解液不同，按照本发明的观点，使用纯盐酸基的电解液的液流电池中，上述这些杂质的存在对于电解液的性能的影响较小，因此，作为纯盐酸的电解液，可以允许这些杂质在一定范围内的存在而无需去除。另外，从进一步减少杂质的影响的角度考虑，对于一些源自贵金 属的杂质，在本发明优选的实施方案中，其含在通式(1)组成的钒的氧化物中的含量为100ppm以下，优选为50ppm以下，更优选为30ppm以下。
本发明中，对于使用通式(1)组成的钒的氧化物作为电解液制备的直接原料，对于工业生产电解液是非常有利的，一方面，对于提供这样的钒的氧化物厂商而言，在还原V 2O 5的过程中只要将钒的氧化态控制在一定范围即可。因此，并无需特别精确的控制还原反应中还原剂与V 2O 5的配合量，减少了发生还原不足或者过度还原的风险，有利于成本的降低，并将该效应传导到下游工业生产中。另外，如上所述，对于通式(1)组成的钒的氧化物的纯度没有过高的限制，因此，在本发明中实际上也能够扩大获得制备全钒液流电池电解液的直接原料的来源，有利于进一步降低成本。
对于通式(1)所表示的钒的氧化物，在本发明一些优选的实施方案中，其中的钒的平均价态优选为+3.3～+3.6，在另一些优选的实施方案中，钒的平均价态优选为+3.3～+3.5，进一步优选为+3.4～+3.5。
对于以上所述的平均价态，应当理解为是统计学上的数据，即这些钒的氧化物是低价钒例如+3价及以下价态的钒与+4价及以上价态的钒的混合氧化物体系。
酸性溶液
本发明中，将上述通式(1)组成的钒的氧化物溶解于酸性溶液中以制备电解液。
本发明所使用的酸性溶液为盐酸溶液，在一些优选的实施方案中，这样的盐酸溶液具有10质量％～38质量％的浓度，在另外一些优选的实施方案中，这样的盐酸溶液具有10质量％～35质量％的浓度。
本发明中，使用盐酸溶液替代硫酸作为酸性溶液，一方面是考虑对钒的氧化物的溶解性相对更为优良，另一方面，考虑的是，尽管使用了盐酸作为酸性溶液，但由于使用的氧化物中钒的价态介于+3.2价～+3.7价之间，因此，并不会有由于钒的氧化价过高而导致对氯离子的氧化，进而也能够避免不期望的氯气的产生。
进一步，使用盐酸作为酸性溶液，避免使用传统的硫酸，是由于按照本 发明的观点，纯盐酸基电解液相比硫酸基电解液具有如下优点：形成的电解液粘度较低，流动性更好；形成的电解液电导性更好，有助于提高电池效率。另外，在电堆内部局部发生过充的情况下，硫酸基电解液对石墨双极板的腐蚀是不可逆的，而同样情况下，盐酸基电解液会产生氯气，而产生的氯气可以通过附加的电解液罐的排气设计，排除体系之外或者被收集，不会对电堆及整个系统造成不可逆的影响。
电解液的配制
本发明中将通式(1)的钒的氧化物与盐酸进行混合溶解。对于混合所使用的设备，没有特殊的要求，可以使用本领域通常的混合设备，例如配置有入料口的反应槽。在本发明一些优选的实施方案中，这些设备除了具有进料装置以外，还具有搅拌装置。对于反应温度，优选为在室温以下，更优选为20℃以下。
在一些优选的实施方案中，将钒的氧化物分散于盐酸溶液进行溶解，进行如下反应：
V xO y+HCl→VCl x+H 2O
在上述反应形成的电解液中，实际上存在着多种价态的钒的氯化物，在一些情况下，如果得到的电解液中还同时存在高价的钒(+5价)离子与低价钒离子(+2价)，则这样的离子间将马上进行氧化还原反应，从而得到全部由+3价以及+4价钒离子组成的电解液。
以氧化物中钒的平均价态为+3.5的情况为例：
V 2O 3.5+7HCl→2VCl 3.5+3.5H 2O
此处的VCl 3.5是统计学上的平均数值，在一些情况下，这样的组成基本上可以视为由VCl 3与VOCl 2按照1:1的比例混合而成。因此，可以理解，当使用V 2O 3.5(V平均价态为+3.5)与盐酸进行混合时，直接得到了全部由+3价钒离子与+4价钒离子形成的电解液，而这样的电解液可以称之为平衡态电解液。
在本发明其他的实施方案中，可以使用平均价态低于+3.5价并在+3.2价以上的钒的氧化物作为原料与盐酸进行反应。在得到的电解液中，同样得到 全部由+3价钒离子与+4价钒离子形成的电解液，与上述V 2O 3.5情况不同的是，在这样的体系中，+3价的钒离子的含量多于+4价钒离子的含量，对于这样的电解液，可以称之为负向非平衡电极液。
在本发明其他的实施方案中，可以使用平均价态高于+3.5价并在+3.7价以下的钒的氧化物作为原料与盐酸进行反应。在得到的电解液中，同样为全部由+3价钒离子与+4价钒离子形成的电解液，与上述V 2O 3.5情况不同的是，在这样的体系中，+3价的钒离子的含量低于+4价钒离子的含量，对于这样的电解液，可以称之为正向非平衡电解液。
因此，可以看出，根据以通式(1)的钒的氧化物为直接原料的电解液的制备中，可以根据实际原料的组成而直接得到平衡态电解液、负向非平衡态电解液以及正向非平衡态电解液。
对于平衡态电解液可以配合以下将介绍的具有催化活化性的金属离子的存在下进行直接使用。在本发明另外的一些实施方案中，可以使用负向非平衡态电解液，尤其的，在倾向于更高程度的充电状态时，可以适当的采用负向非平衡态电解液，或者采用平衡态电解液与负向非平衡态电解液按照一定比例进行混合得到。在本发明的另外一些实施方案中，在得到正向非平衡态电解液的条件下，也可以根据需要使用适当的还原剂对高价钒离子进行还原处理，得到平衡态电解液或者负向非平衡态电解液。对于还原的方法，不受限制的，可以是用本领域常规的还原手段，例如可以使用还原性气体或者其他还原性化合物。可以列举的还原性气体例如氢气，CO，硫化氢，甲烷，二氧化硫，乙烯或NH 3中的一种或任意组合；对于其他的还原性化合物，可以列举的是，醛类物质、醇类物质或者还原性有机酸类物质，典型地例如可以使用草酸等，在另外的一些实施方案中，也可以加入低价钒的氧化物，例如V 2O 3来提高+3价钒离子的含量。
本发明中，作为制备全钒液流电池电解液的直接原料，将通式(1)的氧化物中的钒的平均价态确定为+3.2价～+3.7价是必要的。一方面，通过以上说明，可以看出，这样的原料较为容易的获得，具有较低的成本，并且与本发明的方法具有优异的适配性；另一方面，如果氧化物中钒的氧化态过高或 者过低，则对于形成的非平衡态的电解液的使用将造成明显的限制，并且在对这样的电解液进行后续利用时需要额外的付出过多的生产成本。
另外，在使用通式(1)所表示的钒的氧化物与盐酸进行反应时，可以根据实际需要对反应液进行稀释。在反应的初期为了使得反应能够快速进行，通常使用浓度较高的盐酸溶液以及大量的钒的氧化物。这样得到的电解液中，具有较高的钒离子浓度。而通常情况下，需要将这样的电解液进行进一步的稀释才能够使用。因此，不受限制的，本发明的方法中，在形成电解液的任意步骤中可以使用水进行稀释，优选的，所述稀释的步骤为在酸性溶液与氧化物接触之后进行，更优选的，所述稀释的步骤在酸性溶液与氧化物反应完毕之后进行。在本发明一些优选的实施方案中，所述水为去离子水或蒸馏水。
活化催化剂
本发明的方法，将通式(1)组成的钒的氧化物与酸性溶液混合制备电解液是在活化催化剂的存在下进行的。
对于活化催化剂，可以为金属离子，这些金属离子能够对+3价钒与+2价钒的相互转换起到促进作用。本发明中，作为活化催化剂的金属离子可以为源自Mo、Mn、Pb、Bi的一种或多种离子。在一些优选的实施方案中，这些金属离子的用量为0.1ppm以上，或者0.3ppm以上，或者0.5ppm以上，或者0.7ppm以上，或者1.0ppm以上，或者3.0ppm以上，或者10ppm以上，或者30ppm以上，或者50ppm以上，并且可以为800ppm以下，或者500ppm以下，或者300ppm以下，或者100ppm以下。
本发明中对于所述活化催化剂的加入时间没有特别的限制，在一些实施方案中，可以将活化催化剂离子预先加入到酸性溶液中，然后将该酸性溶液与通式(1)组成的钒的氧化物进行混合以得到电解液。
在另外一些实施方案中，可以先将通式(1)组成的钒的氧化物与酸性溶液先进行混合，然后再加入活化催化剂以得到电解液。
本发明中，在纯盐酸基的电解液中通过上述催化活化剂的使用，能够在无需独立的外部活化步骤的存在下而正常使用所述电解液。
其他方面
可以实施本发明技术方案的其他方面，尽管作为非必要的手段，但也可以采用本领域中已有的辅助手段，只要不影响本发明的技术效果即可。
在一些实施方案中，尽管本发明对于通式(1)所表示的钒的氧化物的纯度要求不高，但本发明并不排斥使用高纯度的钒的氧化物。对于得到高纯度的通式(1)所表示的钒的氧化物，可以使用本领域通常的方法而得到。例如基于高纯度的氯化氧钒得到高纯度的五氧化二钒，进而通过还原手段而得到高纯度的通式(1)所表示的钒的氧化物。
另外，本发明中，在使用含有金属杂质的钒的氧化物作为直接原料的情况下，也可以在作为直接原料的钒的氧化物溶解于酸性物质之后，对其形成的电解液进行进一步的纯化。对于所述纯化步骤，优选的是在未加入以上所述的活化催化剂的情况下进行的。对于所述纯化步骤，没有特别的限定，可以使用本领通常的化学纯化方法以及化学-电化学纯化方法，典型的例如使用电解法或者离子交换法等。
此外，尽管如上所述，实现本发明的技术效果并不依赖于独立的外部活化装置，但在一些实施方案中，也可以在得到含有或者不含有上述活化催化剂的电解液后使用独立的活化步骤进行外部活化。所述活化的方法可以使用现有技术中已有的活化方法，例如，可以使用紫外线活化、微波活化等方式。
在根据本发明的方法得到的电解液中，不受限制的，可以使用本领域常规的各种添加剂，例如络合剂、稳定剂等成分。
<第二实施方式>
本发明的第二实施方式提供了一种液流电池的制备方法，这样的方法包括了根据<第一实施方式>所述的电解液的制备方法。
不受限制的，本发明的第二实施方案中，除了电解液的制备步骤以外，其他步骤均可以使用本领域已有的方法进行。
实施例
以下将对本发明具体的实施例进行描述，需要说明的是，以下实施例仅 仅是对本发明的实施方式的具体举例而不能作为对本发明内容的限制。
参考例1(纯盐酸与纯硫酸电解液的极化比较)：
a).使用4M的HCl和3M的H 2SO 4作为电解液模拟过充条件下电解液对石墨双极板的腐蚀对比。
从图2和图3中可以看出，纯硫酸电解液的情况下，在相同电压下，电流密度具有增大的趋势，并且，纯硫酸电解液对于电池元件具有更大的损伤的趋势。
b).使用4M的HCl和3M的H 2SO 4作为电解液液模拟过充条件下电解液对石墨双极板的腐蚀对比，测试结果参见表1、表2以及图4-5。
实验条件：
电解质：4M的HCl和3M的H 2SO 4
双极板：石墨双极板
双极板极化区域：2cmx2cm
搅拌速度：400rpm
温度：室温25℃
极化电压：2/2.5/3/3.5/4V
表1：使用3M的H 2SO 4的情况(电流密度和电极电势为在极化电压下保持10分钟后的数据)
Figure PCTCN2019100830-appb-000001
表2：使用4M的HCl的情况(电流密度和电极电势为在极化电压下保持10分钟后的数据)
Figure PCTCN2019100830-appb-000002
以上表1和表2，以及说明书附图4和附图5，可以看出使用纯硫酸电解液相比较使用纯盐酸更具有损坏电堆设备元件的倾向(在每个极化电压下保持10分钟)。
以上参考例1的极化实验作为极端过充条件下的模拟实验，模拟了电堆内部在局部过充条件下，不同电解液环境对石墨双极板腐蚀所产生的影响。
实施例1：
使用平均组成为V 2O 3.5粉体，分批次倒入3.1L工业用浓盐酸(38质量％)，过程中匀速搅拌，利用加热装置保持温度在85℃，待粉体全部溶解于盐酸后，加入6.2L去离子水。经过滤，并加入含有Mo 6+和Mn 2+的混合离子作为活化催化剂，且上述混合离子总量为50ppm。得到最终1.15mol/L V 3.5+-4mol/L HCl，进而得到平衡态电解液。下图6为使用制得的电解液对液流电池做的极化曲线。其中y轴单位为电压V，x轴单位为电流密度A/cm 2。分别对电池做充放电极化，将得到的数据点做直线拟合，所得拟合直线的斜率即为充放电时电池内部的等效电阻。从图6中可以看出，利用加入催化剂的电解液，电池的等效内阻为1.0735/-1.0956Ohm·cm 2。
对电池进行充放电循环，下列表3为电池的各项充放电效率数据。
表3
Figure PCTCN2019100830-appb-000003
比较例1
除了不加入活化催化剂以外，与实施例1进行相同的操作，下图7为使用制得的无催化剂电解液对液流电池做的极化曲线。其中y轴单位为电压V，x轴单位为电流密度A/cm 2。分别对电池做充放电极化，将得到的数据点做直线拟合，所得拟合直线的斜率即为充放电时电池内部的等效电阻。从图7中可以看出，不含任何催化剂的电解液，电池的等效内阻为2.504/-2.7811Ohm·cm 2，明显高于实例1中加入催化剂的电池等效内阻。
对电池进行充放电循环，下列表4为电池的各项充放电效率数据。由等效电阻的比较可以得知，电池内阻较高，其电压效率降低，导致整体的能量效率降低。比较下表4中的电池各项效率以及实施例1表3中的电池效率，可以明显看出加入催化剂可以大大提高电池性能。
表4
Figure PCTCN2019100830-appb-000004
实施例2和比较例2(纯硫酸基与纯盐酸基电解液的性能比较)
其中实施例2为根据与实施例1类似的方法得到电解液，其组成为0.75M的V 4+以及0.75M的V 3+，和4M的HCl。
比较例2采用现有技术已知的办法，使用五氧化二矾与硫酸反应，室温下配制电解液(并与实施例1加入同样的活化催化离子)，其组成为0.75M的V 4+以及0.75M的V 3+，和3M的H 2SO 4。
分别使用上述实施例2以及比较例2模拟纯盐酸基与纯硫酸基电解液，并进行测试，测试结果参见表。
其中表5表示实施例2电解液测试情况，表6表示比较例2的电解液测试情况。
表5：
Figure PCTCN2019100830-appb-000005
表6：
Figure PCTCN2019100830-appb-000006
(注：这里之所以采用3M的硫酸溶液和4M的盐酸溶液是因为这两个浓度是硫酸基和盐酸基电解液各自最常用的酸液浓度)
通过对比电流效率/电压效率/能量效率可以得出，盐酸基电解液的电压效率和整体能量效率都显著高于硫酸基电解液。
参考例2
与比较例2进行相同的制备过程，仅仅在于在电解液中不使用所述活化催化剂。
对得到的电解液进行测试，如下表7：
表7：
Figure PCTCN2019100830-appb-000007
将实施例1与比较例1进行比较，并且将比较例2与参考例2进行比较。可以看出，在相同的条件下，无论盐酸基还是硫酸基电解液，活化催化剂的使用对于电压效率以及整体能量效率均有明显的提高，但对于盐酸基的电解液而言，使用活化催化剂后提高的效果更为明显。也整体上体现出了在盐酸基电解液中使用活性催化剂更具有使用价值。
产业上的可利用性
本发明所提供的方法能够在工业上简单高效地制备全钒液流电池用电解液，并制备全钒液流电池。

Claims (6)

  1. 一种液流电池电解液的制备方法，其特征在于，所述方法包括如下步骤：
    a.提供如下通式(1)组成的钒的氧化物的步骤：
    V xO y……..(1)
    其中，V的平均价态为+3.2价～+3.7价，x:y＝1：(1.6～1.85)；
    b.将上述通式(1)组成的钒的氧化物溶解于盐酸溶液，待反应完毕，获得盐酸基钒电解液的步骤，
    所述电解液中还包括选自源自Mo、Mn、Pb、Bi的一种或多种离子。
  2. 根据权利要求1所述的方法，其特征在于，所述V的平均价态为+3.3～+3.5价。
  3. 根据权利要求1或2所述的方法，其特征在于，所述盐酸溶液的浓度为10～38质量％。
  4. 根据权利要求1或2所述的方法，其特征在于，在a步骤前，还包括如下步骤：
    将高氧化价的钒的氧化物进行还原反应以得到所述通式(1)组成的钒的氧化物的步骤，优选地，所述高氧化价的钒的氧化物包括V 2O 5。
  5. 根据权利要求3所述的方法，其特征在于，所述将高氧化价的钒的氧化物进行还原反应是在还原性气体存在下进行的，优选地，所述还原性气体为H 2，CO，硫化氢，甲烷，二氧化硫，乙烯或NH 3中的一种或任意组合。
  6. 一种液流电池的制备方法，其特征在于，其包括根据权利要求1-5任一项的电解液的制备方法。
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