KR102519292B1 - Electrolyte for vanadium redox flow battery and manufacturing method thereof - Google Patents

Abstract

An object of the present invention is to provide an electrolyte solution for a vanadium redox flow battery having a low-cost and high-purity vanadium oxidation number between 3 and 4 by one-step reaction without using an electrochemical reduction method or a metal reducing agent. The present invention relates to a method for preparing an electrolyte solution for a vanadium redox flow battery comprising the step of preparing a vanadium electrolyte having a vanadium oxidation number between 3 and 4 by mixing and reacting a plurality of vanadium oxides having different oxidation numbers in an acidic solution, and the same Provided is an electrolyte solution for a vanadium redox flow battery prepared by the manufacturing method.

Description

Electrolyte for vanadium redox flow battery and manufacturing method thereof

The present invention relates to a vanadium redox flow battery, and more particularly, to an electrolyte solution for a vanadium redox flow battery having a vanadium oxidation number between trivalent and tetravalent in a one-step reaction and a method for manufacturing the same will be.

Vanadium redox flow battery is a water-based secondary battery system that can fundamentally solve the risk of fire and explosion, can stack by stacking multiple electrodes, and has the advantage of freely designing output and energy capacity by melting the active material in the electrolyte. It is a system that has

The electrolyte used in the vanadium redox flow battery is mainly an electrolyte solution in which vanadium ions with a concentration of about 1.5 to 1.7M are dissolved in an acidic solution in which vanadium oxides of trivalent and tetravalent vanadium are mixed in a 1:1 ratio (V ^3.5+ ).

In order to prepare such a 3.5 valent vanadium electrolyte (VO ²⁺ /V ³⁺ = 1/1), a process of preparing a 3.5 valent vanadium electrolyte is generally performed through an electrochemical or chemical reduction reaction after preparing a 4-valent vanadium electrolyte. It is being used.

In general, a tetravalent vanadium electrolyte is produced by applying a chemical reducing agent using inexpensive V ₂ O ₅ raw materials. electrolyte solution can be prepared.

However, when such a metal reducing agent is used, problems of side reactions and performance degradation may occur due to the presence of metal impurities in the prepared electrolyte.

In order to solve this problem, a method of preparing a trivalent vanadium electrolyte using a tetravalent electrolyte through an electrochemical method is most widely used. The electrochemical reduction reaction may be free of impurities and stably produce an electrolyte.

However, the gaseous chemical reduction reaction requires an additional electrochemical reactor, takes a long reaction time, and requires an additional chemical reduction reaction of the pentavalent electrolyte generated at the anode, so it has a problem of having a very complicated process. .

Publication No. 2019-0124865 (2019.11.06.)

Therefore, an object of the present invention is to provide an electrolyte solution for a vanadium redox flow battery having a low-cost and high-purity vanadium oxidation number between trivalent and tetravalent in a one-step reaction without using an electrochemical reduction method or a metal reducing agent and a method for manufacturing the same there is.

Another object of the present invention is to provide an electrolyte for a vanadium redox flow battery capable of controlling the oxidation number of vanadium and a method for manufacturing the same.

In order to achieve the above object, the present invention is a step of preparing a vanadium electrolyte having a vanadium oxidation number between 3 and 4 by mixing and reacting a plurality of vanadium oxides having different oxidation numbers in an acidic solution; vanadium redox including Provided is a method for preparing an electrolyte solution for a flow battery.

In the preparing step, an organic reducing agent may be additionally added to the acidic solution.

The vanadium oxide is at least two selected from the group consisting of V ₂ O ₅ , V ₂ O ₃ and V ₂ O ₄ .

The organic reducing agent is at least one selected from the group consisting of formic acid, formaldehyde, methanol, ethanol, oxalic acid and ammonium hydroxide.

The vanadium oxide may be V ₂ O ₅ and V ₂ O ₃ .

In the preparing step, as the input amount of the organic reducing agent increases in proportion to the increase in the molar ratio of V ₂ O ₅ /V ₂ O ₃ , the oxidation number of vanadium increases and the concentration of vanadium decreases.

In the preparing step, the vanadium oxidation number of the prepared vanadium electrolyte may be adjusted by adjusting the molar ratio of V ₂ O ₅ /V ₂ O ₃ and the input amount of the organic reducing agent.

The acidic solution is at least one selected from the group consisting of sulfuric acid, hydrochloric acid, nitric acid and phosphoric acid.

In addition, the present invention provides an electrolyte for a vanadium redox flow battery including a vanadium electrolyte having a vanadium oxidation number between 3 and 4, prepared by mixing and reacting a plurality of vanadium oxides having different oxidation numbers in an acidic solution.

According to the present invention, a vanadium electrolyte having a vanadium oxidation number between 3 and 4 can be prepared by mixing and reacting a plurality of vanadium oxides having different oxidation numbers in an acidic solution.

According to the production method according to the present invention, a low-cost and high-purity vanadium electrolyte having an oxidation number between trivalent and tetravalent vanadium electrolyte can be prepared by a one-step reaction using an oxidizing solution without using an electrochemical reduction method or a metal reducing agent. can That is, since the 3.5 vanadium electrolyte can be prepared by reacting the vanadium oxide of V ₂ O ₅ and V ₂ O ₃ with an acidic solution, the manufacturing process of the vanadium electrolyte can be simplified and a high-purity vanadium electrolyte can be produced without generating additional impurities. can

In addition, in the process of mixing and reacting a plurality of vanadium oxides having different oxidation numbers in an acidic solution, the vanadium oxidation number of the prepared vanadium electrolyte can be easily controlled by adjusting the ratio of the plurality of vanadium oxides having different oxidation numbers and the amount of the organic reducing agent. .

1 is a graph showing charge/reversal characteristics of a vanadium redox flow battery to which an electrolyte solution according to a comparative example is applied.
2 is a graph showing charge/reverse characteristics of a vanadium redox flow battery to which an electrolyte solution according to an embodiment is applied.
3 is a graph showing life characteristics of a vanadium redox flow battery to which an electrolyte solution according to an embodiment is applied.

It should be noted that in the following description, only parts necessary for understanding the embodiments of the present invention are described, and descriptions of other parts will be omitted without departing from the gist of the present invention.

The terms or words used in this specification and claims described below should not be construed as being limited to ordinary or dictionary meanings, and the inventors have appropriately used the concept of terms to describe their inventions in the best way. It should be interpreted as a meaning and concept consistent with the technical spirit of the present invention based on the principle that it can be defined in the following way. Therefore, the embodiments described in this specification and the configurations shown in the drawings are only preferred embodiments of the present invention, and do not represent all of the technical spirit of the present invention, so various equivalents that can replace them at the time of the present application. It should be understood that there may be variations and variations.

Hereinafter, embodiments of the present invention will be described in more detail with reference to the accompanying drawings.

The present invention provides a method for preparing an electrolyte solution for a vanadium redox flow battery comprising the step of preparing a vanadium electrolyte solution having a vanadium oxidation number between 3 and 4 by mixing and reacting a plurality of vanadium oxides having different oxidation numbers in an acidic solution do.

In the manufacturing step, a vanadium electrolyte may be prepared by stirring a mixture of a plurality of vanadium oxides having different oxidation numbers and an acidic solution at 80° C. or higher for 1 to 12 hours and then cooling. Stirring is preferably performed for 5 hours or longer.

According to the method for preparing a vanadium electrolyte according to the present invention, a low-cost and high-purity vanadium electrolyte having a vanadium oxidation number between trivalent and tetravalent by one-step reaction using an oxidizing solution without using an electrochemical reduction method or a metal reducing agent can be manufactured.

In the production method according to the present invention, an organic reducing agent may be additionally added in the step of preparing the vanadium electrolyte.

In the process of mixing and reacting a plurality of vanadium oxides having different oxidation numbers in an acidic solution, the vanadium oxidation number of the prepared vanadium electrolyte can be easily controlled by adjusting the ratio of the plurality of vanadium oxides having different oxidation numbers and the amount of the organic reducing agent. there is.

The method for preparing the vanadium electrolyte according to the present invention will be described in detail.

Vanadium oxide may be two or more selected from the group consisting of V ₂ O ₅ , V ₂ O ₃ and V ₂ O ₄ . For example, V ₂ O ₅ and V ₂ O ₃ may be used as vanadium oxide.

The organic reducing agent may be at least one selected from the group consisting of formic acid, formaldehyde, methanol, ethanol, oxalic acid, and ammonium hydroxide, but is not limited thereto.

In addition, at least one selected from the group consisting of sulfuric acid, hydrochloric acid, nitric acid and phosphoric acid may be used as the acidic solution.

Here, in the case of using V ₂ O ₅ and V ₂ O ₃ as vanadium oxide, the vanadium electrolyte may be prepared according to the following chemical formula.

[chemical formula]

V ₂ O ₅ + 3V ₂ O ₃ + 10H ₂ SO ₄ → 4VO ²⁺ + 4V ³⁺ + 10SO ₄ ^2- + 10H ₂ O

According to the chemical formula, ^a reduction reaction of vanadium pentavalent ions ( _{VO 2 + )} to vanadium tetravalent ions (VO ²⁺ ) and vanadium trivalent ions (V ³⁺ ) using the oxidation reaction of V 2 O 3 , and V A vanadium electrolyte solution of V ^3.5+ may be prepared through a dissolution reaction of ₂ O ₃ .

For example, when V ₂ O ₅ is reacted with V ₂ O ₃ under sulfuric acid conditions, V ₂ O ₅ and V ₂ O ₃ are reacted at a ratio of 1:3 based on the fact that 5-valent vanadium is reduced to 4-valent. A vanadium electrolyte solution can be prepared.

Thus, the vanadium electrolyte prepared by the manufacturing method according to the present invention has the advantage of not generating an excess 5-valent vanadium electrolyte compared to the electrochemical reduction method and containing no impurities compared to the chemical manufacturing method using a metal reducing agent. That is, according to the manufacturing method according to the present invention, a high-purity vanadium electrolyte having a vanadium oxidation number between 3 and 4 can be manufactured through a simple manufacturing process.

[Examples and Comparative Examples]

In order to confirm the chemical characteristics of the vanadium electrolyte according to the present invention, vanadium electrolytes according to Examples 1 to 5 were prepared. Changes in vanadium oxidation number and vanadium concentration of the prepared vanadium electrolyte were measured.

Example 1

In the process of preparing a vanadium electrolyte by reacting V ₂ O ₅ with V ₂ O ₃ under sulfuric acid conditions, changes in vanadium oxidation number and vanadium concentration with respect to reaction time were compared.

Vanadium electrolyte according to Example 1 was prepared by adding reactants to 4.5M sulfuric acid solution (20 ml) at a weight ratio of 4.5/1 of V ₂ O ₃ and V ₂ O ₅ , stirring for 1 to 12 hours at a temperature of 80 ° C or higher and then cooling. did

Referring to Table 1 below, it was confirmed that the vanadium electrolyte according to Example 1 lowered the oxidation number and increased the concentration as the reaction time increased, and it was confirmed that there was no change in concentration and oxidation number after 6 hours of reaction time.

Example 2

In the process of preparing a vanadium electrolyte by reacting V ₂ O ₅ with V ₂ O ₃ under sulfuric acid conditions, changes in vanadium oxidation number and vanadium concentration with respect to reaction time were compared.

Vanadium electrolyte according to Example 2 was prepared by adding reactants to 4.5M sulfuric acid solution (20 ml) at a weight ratio of 3/1 of V ₂ O ₃ and V ₂ O ₅ , stirring at a temperature of 80 ° C. or higher for 6 to 9 hours, and then cooling. did

Referring to Table 2 below, it was confirmed that the vanadium electrolyte according to Example 2 did not show significant changes in vanadium concentration and vanadium oxidation number after 6 hours of reaction time. It was confirmed that a vanadium electrolyte having a vanadium oxidation number of 3.5 and a vanadium concentration of about 1.7M can be prepared under the condition of a weight ratio of V ₂ O ₃ and V ₂ O ₅ of 3/1.

Example 3

In the process of preparing a vanadium electrolyte by reacting V ₂ O ₅ with V ₂ O ₃ under sulfuric acid conditions, changes in vanadium oxidation number and vanadium concentration versus sulfuric acid molar concentration were compared.

Vanadium electrolyte according to Example 3 was prepared by adding a reactant to a 3.0-4.5M sulfuric acid solution (20 ml) at a weight ratio of 3/1 of V ₂ O ₃ and V ₂ O ₅ , stirring for 6 hours at a temperature of 80 ° C or higher, and then cooling. did

Referring to Table 3 below, it was confirmed that the vanadium electrolyte according to Example 3 did not significantly differ in the vanadium oxidation number and vanadium concentration according to the sulfuric acid concentration.

Example 4

In the process of preparing a vanadium electrolyte by reacting V ₂ O ₅ with V ₂ O ₃ under sulfuric acid conditions, the V ₂ O ₅ /V ₂ O ₃ molar ratio and the vanadium oxidation number and vanadium concentration change for the organic reducing agent (oxalic acid) were compared.

In 4.5M sulfuric acid solution (20 ml), the reactant was added at a molar ratio of 1/3 to 1/1 of V ₂ O ₅ and V ₂ O ₃ , and 0.8 to 1.1 equivalent of oxalic acid, an organic reducing agent, was added and stirred at a temperature of 80 ° C or higher for 5 hours. After cooling, a vanadium electrolyte solution according to Example 4 was prepared.

Referring to Table 4 below, it was confirmed that the vanadium oxidation number of the vanadium electrolyte according to Example 4 was lowered according to the addition of the reducing agent, and the vanadium oxidation number was reduced by adjusting the V ₂ O ₅ /V ₂ O ₃ molar ratio and the organic reducing agent (oxalic acid). It was confirmed that control of

Example 5

Changes in vanadium oxidation number and vanadium concentration for organic reducing agent (oxalic acid) under the condition of 1/1 molar ratio of V _{2 O 5 /} V 2 O ₃ in the process of preparing vanadium electrolyte by reacting _{V 2} O 5 with V ₂ O ₃ under sulfuric acid conditions compared.

In 4.5M sulfuric acid solution (20 ml), the reactant was added at a molar ratio of 1/1 of V ₂ O ₅ and V ₂ O ₃ , and 1.1 to 1.3 equivalents of oxalic acid, an organic reducing agent, was added, stirred at a temperature of 80 ° C or higher for 5 hours, and then cooled. A vanadium electrolyte solution according to Example 5 was prepared.

Referring to Table 5 below, it was confirmed that the vanadium electrolyte according to Example 5 can control the desired vanadium oxidation number of 3.5 and vanadium concentration of 1.7M by adjusting oxalic acid under the condition of 1/1 molar ratio of V ₂ O ₅ /V ₂ O ₃ .

In order to confirm the electrical characteristics of the vanadium electrolyte according to the present invention, vanadium electrolytes according to Examples and Comparative Examples were prepared as described above. A vanadium redox flow battery was prepared by applying the prepared vanadium electrolyte, and then charge/discharge characteristics and lifespan characteristics were evaluated.

The vanadium relox flow battery was manufactured in a form having a unit cell. Heat-treated carbon felt was used as the electrode of the unit cell, graphite was used as the bipolar plate, and Nafion 117 was used as the ion exchange membrane.

In addition, 80mL of 1.7M concentration was applied as the vanadium electrolyte, and the charge/discharge characteristics and lifespan characteristics were observed, and the results are shown in FIGS. 1 to 3. The vanadium redox flow battery according to the embodiment used the vanadium electrolyte having a vanadium oxidation number of 3.5 and a vanadium concentration of 1.7M according to Example 5 as a vanadium electrolyte.

1 is a graph showing charge/reversal characteristics of a vanadium redox flow battery to which a vanadium electrolyte solution according to a comparative example is applied. 2 is a graph showing charge/reverse characteristics of a vanadium redox flow battery to which a vanadium electrolyte solution according to an embodiment is applied. 3 is a graph showing life characteristics of a vanadium redox flow battery to which a vanadium electrolyte according to an embodiment is applied.

1 to 3, the vanadium redox flow battery to which the conventional electrolytic reduction electrolyte according to the comparative example was applied showed a capacity characteristic of about 2,900 mAh under a current density of 80 mA / cm ² condition, and an energy efficiency characteristic of 83.5 % and 80 mA/cm ² levels.

On the other hand, the vanadium redox flow battery to which the vanadium electrolyte according to the embodiment was applied showed capacity characteristics of about 3,000 mAh under a current density of 80 mA/cm ² , and energy efficiency characteristics of 84.9% and 80 mA/cm ² . , compared to the battery according to the comparative example, exhibited excellent capacity characteristics and energy efficiency characteristics.

Therefore, it can be confirmed that the manufacturing process of the vanadium electrolyte according to the present invention is not only simple, but also exhibits excellent cell characteristics when applied to a vanadium redox flow battery.

On the other hand, the embodiments disclosed in this specification and drawings are only presented as specific examples to aid understanding, and are not intended to limit the scope of the present invention. In addition to the embodiments disclosed herein, it is obvious to those skilled in the art that other modifications based on the technical idea of the present invention can be implemented.

Claims (12)

preparing a vanadium electrolyte solution having a vanadium oxidation number between 3 and 4 by mixing and reacting a plurality of vanadium oxides having different oxidation numbers in an acidic solution;
Method for producing an electrolyte solution for a vanadium redox flow battery comprising a. The method of claim 1, wherein in the manufacturing step,
A method for producing an electrolyte solution for a vanadium redox flow battery, characterized in that an organic reducing agent is additionally added to the acidic solution. According to claim 1 or 2,
The vanadium oxide is a method for producing an electrolyte solution for a vanadium redox flow battery, characterized in that at least two selected from the group consisting of V ₂ O ₅ , V ₂ O ₃ and V ₂ O ₄ . According to claim 2,
The organic reducing agent is a method for producing an electrolyte solution for a vanadium redox flow battery, characterized in that at least one selected from the group consisting of formic acid, formaldehyde, methanol, ethanol, oxalic acid and ammonium hydroxide. According to claim 1 or 2,
The vanadium oxide is a method for producing an electrolyte solution for a vanadium redox flow battery, characterized in that V ₂ O ₅ and V ₂ O ₃ . The method of claim 5, wherein in the manufacturing step,
A method for producing an electrolyte solution for a vanadium redox flow battery, characterized in that the vanadium oxidation number increases and the vanadium concentration decreases as the input amount of the organic reducing agent increases in proportion to the increase in the molar ratio of V ₂ O ₅ /V ₂ O ₃ . The method of claim 5, wherein in the manufacturing step,
A method for producing an electrolyte solution for a vanadium redox flow battery, characterized in that by controlling the vanadium oxidation number of the prepared vanadium electrolyte by adjusting the molar ratio of V ₂ O ₅ /V ₂ O ₃ and the input amount of the organic reducing agent. According to claim 1 or 2,
The acidic solution is a method for producing an electrolyte solution for a vanadium redox flow battery, characterized in that at least one selected from the group consisting of sulfuric acid, hydrochloric acid, nitric acid and phosphoric acid. delete delete delete delete

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