KR20110064058A - Redox flow battery electrolyte and production method thereof and redox flow battery produced thereby - Google Patents

Abstract

PURPOSE: A method for preparing redox flow battery electrolyte is provided to lower manufacturing costs, to easily prepare electrolyte, and to accurately control the added amount of vanadium within a solution. CONSTITUTION: A method for preparing redox flow battery electrolyte, H2SO4 to which VOSO4 is added or H3PO4 to which VOHPO4 is added, used in redox flow comprises the steps of: adding a vanadium compound as a starting material to distilled water and stirring the mixture; adding a reducing agent to a vanadium compound aqueous solution in which the starting material is included; and adding H2SO4 or H3PO4 phosphoric acid to the reduced material.

Description

REDOX FLOW BATTERY ELECTROLYTE AND PRODUCTION METHOD THEREOF AND REDOX FLOW BATTERY PRODUCED THEREBY}

The present invention relates to a method of preparing H ₂ SO ₄ electrolyte in which VOSO ₄ is dissolved or H ₃ PO ₄ electrolyte in which VOHPO ₄ is added, and more particularly, to a vanadium compound aqueous solution by adding a reducing agent to vanadium compound solution. by reduction of the compound, whereby H ₂ SO ₄ or H ₃ PO of the VOSO ₄ the addition of addition of the ₄ prepared H ₂ SO ₄ or VOHPO ₄ the addition of H ₃ PO ₄ made of a liquid electrolyte and a manufacturing method thereof and its les It relates to a dox flow battery.

Recently, renewable energy, such as solar energy and wind energy, has been spotlighted as a method for suppressing greenhouse gas emission, which is a major cause of global warming, and a lot of researches are being carried out for their practical use.

However, renewable energy is greatly affected by the site environment and natural conditions. Furthermore, there is a disadvantage in that the renewable energy cannot supply the energy continuously evenly because the output fluctuates severely.

Therefore, in order to use renewable energy for home or commercial use, a system that stores energy when the output is high and uses the stored energy when the output is low is used.

A large capacity secondary battery is used as such an energy storage system. For example, a large capacity secondary battery storage system is introduced into a large-scale photovoltaic and wind farm.

The secondary battery for storing a large amount of power includes a lead acid battery, a NaS battery, and a redox flow battery (RFB).

The lead acid battery is widely used commercially compared to other batteries, but has disadvantages such as low efficiency and cost of maintenance due to periodic replacement and disposal of industrial waste generated during battery replacement. In the case of NaS battery, the energy efficiency is high, but there is a disadvantage in operating at a high temperature of more than 300 ℃. The redox flow battery has been researched as a large capacity secondary battery recently because it has low maintenance cost, can operate at room temperature, and can independently design capacity and output.

The electrolyte of the redox flow battery is applicable when a substance having a redox couple can be dissolved in the solution and the reaction is reversible. The electrolyte of the early redox battery was used by applying redox pairs of different materials to the positive electrode and the negative electrode, but the capacity decreased due to cross contamination between the ionized materials through the separator during charge and discharge. This has risen.

Therefore, it is suggested to use vanadium together in the anode and cathode as a method to minimize the ion crossover phenomenon. When vanadium is applied to the electrolyte, high battery voltage can be obtained and good cycle life can be obtained.

Conventional vanadium-based electrolyte is usually used by dissolving VOSO ₄ in sulfuric acid mixed with distilled water, and VOSO ₄ is about 10 times more expensive than V ₂ O ₅ and the amount of vanadium in the solution is not constant because the water content in the material is not constant. There is a disadvantage that can not be precisely adjusted.

In order to minimize these disadvantages, Kazacos et al. Published a method for preparing an electrolyte by adding V ₂ O ₅ or vanadium inorganic salt to a solution in which VOSO ₄ is dissolved or in a solution in which VOSO ₄ is not dissolved and then electrolytically reduced (PCT / AU88 / 00471). In addition, a method of preparing an electrolyte by adding an acid containing a reducing agent (oxalic acid) and V ₂ O ₅ to a solution in which VOSO ₄ is dissolved or a sulfuric acid solution containing NH ₄ VO ₃ is added. .

However, since these methods take a long time or have disadvantages in that impurities remain in the electrolyte, a study on a new manufacturing method that can solve the problem is required.

Accordingly, the redox flow battery electrolyte according to the present invention and a method for manufacturing the same and a redox flow battery manufactured therefrom are

By reducing the vanadium compound by adding a reducing agent in the state in which the vanadium compound is not dissolved, and then adding an acid to prepare an electrolyte solution, the manufacturing cost can be lowered, it can be easily and quickly prepared, and the production can accurately control the amount of vanadium in the solution. It is an object of the present invention to provide a method and electrolyte solution and a redox flow battery produced therefrom.

Redox flow battery electrolyte production method of the present invention for solving the above problems,

The starting material LES in the manufacturing method of the electrolyte VOSO ₄ is a H ₂ SO ₄ or VOHPO ₄ added was added H ₃ PO ₄ used in the redox flow cell, and stirred by the addition of the starting material vanadium compound in distilled water, After reducing by adding a reducing agent to the aqueous solution of the vanadium compound contained therein is prepared by adding H ₂ SO ₄ or H ₃ PO ₄ phosphoric acid.

At this time, the starting material is one or more selected from V ₂ O ₅ , V ₂ O ₃ , V ₂ O ₄ , NH ₄ VO ₃ , the reducing agent is a vanadium compound NH ₄ OH in distilled water to which the vanadium compound is added It can be added to the molar ratio of 0.01 to 10 mol relative to change the base of the compound and then to add a reducing agent.

The VOSO ₄ -added H ₂ SO ₄ redox flow battery electrolyte prepared by the above production method had a vanadium concentration of 0.001M to 10M, and a H ₂ SO ₄ concentration of 0.001M to 16M; In the H ₃ PO ₄ redox flow battery electrolyte to which VOHPO ₄ was added, the vanadium concentration was 0.001M to 10M, and the H ₃ PO ₄ concentration was 0.001M to 12M.

Redox flow cell using the electrolyte solution of the present invention can be used in the H ₃ PO ₄ electrolyte of the VOSO ₄ the addition of H ₂ SO ₄ or VOHPO ₄ added in an anode, a cathode, an anode and a cathode.

In addition, it is possible to provide a redox flow battery that is used as an electrolyte solution of a cathode or an anode and a cathode after electrolytic reduction of the electrolyte solution prepared by the present invention.

As described in detail above, the redox flow battery electrolyte of the present invention, a method for manufacturing the same, and a redox flow battery manufactured therefrom are

VOSO ₄ the addition of H ₂ SO ₄ and the VOHPO ₄ is lower vanadium redox electrolyte manufacturing cost of the addition of H ₃ PO _4, easy and fast to impurities can be accurately controlled to within a vanadium addition amount, as well as possible, the electrolyte solution prepared It has the effect of minimizing.

H ₃ PO ₄ in a redox flow battery electrolyte production method is the invention as H ₂ SO ₄ is added according to the VOSO ₄ or VOHPO ₄ is added,

A starting material, a vanadium compound, is added to the distilled water, followed by stirring, and then a reducing agent is added to reduce the starting material, followed by addition of an acid. The acid here uses H ₂ SO ₄ or H ₃ PO ₄ .

The distilled water includes purified distilled water.

As the starting material which is the vanadium compound, V ₂ O ₅ , V ₂ O ₃ , V ₂ O ₄ , NH ₄ VO ₃ are used.

In addition, NH ₄ OH may be added to the vanadium compound aqueous solution before adding the reducing agent to the starting material to change the base of the compound, and then the reducing agent may be added. In this case, the addition ratio of NH ₄ OH may be added in a molar ratio of 0.01 to 10 mol relative to vanadium oxide. That is, when vanadium oxide is added in 0.001M ~ 10M NH ₄ OH may be added in a ratio of 0.01 ~ 10M.

As the reducing agent, N ₂ H ₄ (hydrazine) and N ₂ H ₄ hydrate, HO ₂ CCO ₂ H (oxalic acid) and HO ₂ CCO ₂ H hydrate, NaBH ₄ (sodium borohydride) and NaBH ₄ aqueous solution are used.

That is, the starting material was added to distilled water and stirred thoroughly in the solution, and N ₂ H ₄ (hydrazine) and N ₂ H ₄ hydrate, HO ₂ CCO ₂ H (oxalic acid) and HO ₂ CCO ₂ H hydrate, NaBH ₄ (sodium Reducing agents such as borohydride) and NaBH ₄ aqueous solution are used to reduce the starting materials. After the prepared H ₂ SO ₄ and H ₃ PO ₄ was added to the VOSO ₄ is the addition of H ₂ SO ₄ or ₄ VOHPO adding H ₃ PO _4.

The VOSO ₄ added H ₂ SO ₄ electrolyte prepared by the preparation method has a vanadium molar concentration of 0.001M to 10M, and a H ₂ SO ₄ molar concentration of 0.001M to 16M.

In addition, the H ₃ PO ₄ electrolyte solution to which VOHPO ₄ was added has a vanadium molar concentration of 0.001M to 10M, and a H ₃ PO ₄ molar concentration of 0.001M to 12M.

The redox battery may be manufactured using the electrolyte, and the electrolyte may be used for any one of the positive electrolyte and the negative electrolyte or both the positive and negative electrolytes. In addition, the electrolyte may be used as a cathode electrolyte after electrolytic reduction, or may be used for both the cathode and the cathode electrolyte.

In addition, the capacity of 0.01 to 100㎃h / ㎖ from the scope of the VOSO ₄ the addition of H ₂ SO ₄ electrolyte or VOSO redox flow cell using the electrolyte ₄ are reduced to a H ₂ SO ₄ is added to the electrolyte solution, 0 ~ 2V service, and a redox flow battery used to VOHPO ₄ the addition of H ₃ PO ₄ electrolyte, or electrolytic reduction VOHPO ₄ is a H ₃ PO ₄ electrolyte solution is added a 0.01 to capacity 150㎃ / ㎖ in the range of 0 ~ 2.5V to provide.

Hereinafter, the present invention will be described in more detail with reference to examples, which are only examples presented to aid the understanding of the present invention, and the present invention is not limited thereto.

Example 1

Prepare 100 mL of 3M H ₂ SO ₄ with 1M VOSO ₄ added

First, 69.45 mL of distilled water was prepared.

To this was added 0.5 M (9.19 g) of V ₂ O ₅ (purity: 99%) having an oxidation value of +5 and thoroughly mixed in distilled water.

0.25 M (1.28 mL) of N ₂ H ₄ OH H ₂ O (hydrazine monohydrate, purity: 98%) was added to the mixed vanadium to reduce the oxidation value of vanadium from +5 to + tetravalent. With the addition of N ₂ H ₄ OH H ₂ O the color of the solution changed from pale blue to khaki and finally to a dark brown solution.

To this solution was added H ₂ SO ₄ (purity: 99.999%) 4M (21.32 mL). The reason for the addition of 4M H ₂ SO ₄ is that in the VOSO ₄ have the 3M 1M generated and H ₂ SO ₄ solution. As H ₂ SO ₄ was added, the color of the solution changed from dark brown to dark blue and from dark blue to dark blue, and finally a blue solution was obtained. The solution change of the manufacturing process is shown in FIG. 1.

Example 2

Prepare 100 mL of 6 M H ₂ SO _{4 with 2} M VOSO ₄

In the same manner as in Example 1, 34.03 mL of distilled water, V ₂ O ₅ 1M (18.37 g), N ₂ H ₄ OH ₂ O 0.5M (2.55 mL), and H ₂ SO ₄ 7M (42.64 mL) were added.

The color of the prepared solution was finally blue, but a darker blue solution than Example 1 was obtained.

Example 3

Prepare 100 mL of 5 M H ₃ PO ₄ (purity: 85%) to which 1 M of VOHPO ₄ was added.

In the same manner as in Example 1, 67.67 mL of distilled water, 0.5 M (9.19 g) of V ₂ O ₅ , 0.25 M of N ₂ H ₄ OH ₂ O (1.28 mL), and ₄ M (27.45 mL) of H ₃ PO ₄ were added.

The color of the prepared solution was finally blue, but unlike Examples 1 and 2, a turbid blue solution was obtained. The solution change figure of the manufacturing process is shown in FIG.

Example 4

100 mL of 5 M H ₃ PO _{4 with 3} M of VOHPO ₄ was prepared.

Distilled water 30.47 mL, V ₂ O ₅ 1.5 M (27.56 g), N ₂ H ₄ OH H ₂ O 0.75 M (3.83 mL), and H ₃ PO ₄ 6M (54.9 mL) were added in the same manner as in Example 1. .

The color of the prepared solution was finally blue but a darker blue solution than Example 3 was obtained. However, a solution was obtained in which the solute was not completely dissolved.

Example 5

Prepare 100 mL of 3M H ₂ SO ₄ with 1M VOSO ₄ added

First, 70.62 mL of distilled water was prepared.

0.5 M (9.19 g) of V ₂ O ₅ having an oxidation value of +5 was added thereto and mixed thoroughly in distilled water.

Next, NH ₄ OH (purity: 28%) solution was added with 1M (6.78 mL) and mixed. As the mixing time passes, the color of the V ₂ O ₅ powder in the solution fades.

Thereafter, 0.25 M (1.28 mL) of N ₂ H ₄ OH H ₂ O was added to the mixed vanadium to reduce the oxidation value of vanadium from +5 to + tetravalent. With the addition of N ₂ H ₄ OH H ₂ O the color of the solution changed from pale blue to khaki and finally to a dark brown solution.

To this solution was added 4M (21.32 mL) of H ₂ SO ₄ . As H ₂ SO ₄ was added, the color of the solution changed from dark brown to dark blue and from dark blue to dark blue, and finally a blue solution was obtained.

Example 6

100 mL of 3M H ₃ PO ₄ to which 1M of VOHPO ₄ was added was prepared.

67.67 mL of distilled water, 0.5 M (9.19 g) of V ₂ O _{5, 1} M of NH ₄ OH solution (6.78 mL), 0.25 M of N ₂ H ₄ OH ₂ O (1.28 mL), H ₃ PO ₄ was added 4M (27.45 mL).

The color of the prepared solution obtained a blue solution close to Example 3.

Example 7

Prepare 100 mL of 3M H ₂ SO ₄ with 1M VOSO ₄ added

First, 73.28 mL of distilled water was prepared.

HO ₂ CCO ₂ H (oxalic acid, purity: 99.5%) was added 0.5M (6.34g) and mixed for about 2 hours. The mixed solution was in a state where HO ₂ CCO ₂ H was not completely dissolved in the solution.

0.5 M (9.19 g) of V ₂ O ₅ was added to the solution mixed with HO ₂ CCO ₂ H and mixed in distilled water.

Thereafter, 4M (21.32 mL) was added to H ₂ SO ₄ .

The color of the solution was dark brown to blue for a long time after the addition of H ₂ SO ₄ . However, HO ₂ CCO ₂ H remained in solution.

Example 8

In order to determine the charge and discharge characteristics of the material produced in Example 1, a redox battery was manufactured.

Electrode was used as carbon felt and heat treated at 500 ° C for 5 hours to activate the electrode.

Carbon plates were used as the current collector and Nafion 117 was used as the separator.

The material prepared in Example 1 was used as the positive electrode electrolyte, and the negative electrode electrolyte was used by electrolytic reduction of the material produced in Example 1, wherein the electrolyte solution was used in each 3ml.

The capacity change when the current is applied at 5, 10, 20, 40, 60, 80 mA / cm 2 to the manufactured redox battery is shown in Table 1, wherein the voltage change with time at each current density is shown in FIGS. 3f.

Current density (mA / ㎠) Discharge Capacity (mAh) 5 22.3 10 24.8 20 24.1 40 22.6 60 20.7 80 16.4

Example 9

In order to determine the charge and discharge characteristics of the material produced in Example 1, a redox battery was manufactured in the same manner as in Example 8.

The material produced in Example 1 was used as the positive electrolyte and the negative electrolyte.

The capacity change when a current of 10, 20, 40, 60, 80 mA / cm 2 was applied to the manufactured redox battery is shown in Table 2, wherein the voltage with time at a current density of 10, 20, 40 mA / cm 2 The change is shown in FIGS. 4A-4C.

Current density (mA / ㎠) Discharge Capacity (mAh) 10 63.1 20 33.0 40 1.5 60 0.7 80 0.2

Example 10

In order to determine the charge and discharge characteristics of the material produced in Example 3, a redox battery was manufactured in the same manner as in Example 8.

The material prepared in Example 3 could not be used as anolyte electrolyte because VOHPO ₄ changed to precipitated VOPO ₄ , which is insoluble yellow during charging.

X-ray diffraction pattern of the deposited material is shown in FIG.

Therefore, the material produced in Example 3 was electrolytically reduced and used as the positive electrolyte and the negative electrolyte.

The capacity change when the current is applied at 5, 10, 20, 40, 60, 80 mA / cm 2 to the manufactured redox battery is shown in Table 3, wherein the voltage change with time at each current density is shown in FIGS. 6f.

Current density (mA / ㎠) Discharge Capacity (mAh) 5 49.5 10 49.4 20 39.8 40 27.3 60 13.9 80 4.6

1 is a photograph showing the color change of the solution according to the increase in the amount of H ₂ SO ₄ by the embodiment of the present invention.

Figure 2 is a photograph showing the color change of the solution with increasing amount of H ₃ PO ₄ by an embodiment of the present invention.

3A to 3F are graphs showing voltage changes with time at each current density of a battery using H ₂ SO ₄ to which VOSO ₄ is added as a positive electrolyte in an embodiment of the present invention.

4A to 4C illustrate H ₂ SO ₄ added with VOSO ₄ in the embodiment of the present invention. A graph showing the change in voltage with time at each current density of a battery used as a positive electrolyte and a negative electrolyte.

FIG. 5 is an X-ray diffraction pattern of a precipitated material when H ₃ PO ₄ to which VOHPO ₄ is added is used as an anode electrolyte in an embodiment of the present invention. FIG.

6a to 6f are graphs showing the voltage change with time at each current density of a battery used as an anode electrolyte and a cathode electrolyte by electrolytic reduction of H ₃ PO ₄ to which VOHPO ₄ is added in an embodiment of the present invention.

Claims (10)

In the manufacturing method of the electrolyte VOSO ₄ the addition of H ₂ SO ₄ or VOHPO ₄ is added H ₃ PO ₄ used in the redox flow cell, It is prepared by adding a starting material which is a vanadium compound to distilled water, stirring and reducing the solution by adding a reducing agent to an aqueous solution of vanadium compound containing the starting material, and then adding H ₂ SO ₄ or H ₃ PO ₄ phosphoric acid. Redox flow battery electrolyte production method. The method of claim 1, The starting material V ₂ O ₅ , V ₂ O ₃ , V ₂ O ₄ , NH ₄ VO ₃ One or more kinds of heterogeneous redox flow battery electrolyte production method characterized in that the use of the selection. The method of claim 1, The method of manufacturing a redox flow battery electrolyte, wherein the vanadium compound solution is added with NH ₄ OH to change the base of the compound and then a reducing agent is added. The method of claim 3, wherein The addition rate of the NH ₄ OH is a redox flow battery electrolyte production method, characterized in that added in a molar ratio of 0.01 to 10 mol compared to the vanadium compound. The method according to any one of claims 1 to 3, The reducing agent may be selected from N ₂ H ₄ (hydrazine) and N ₂ H ₄ hydrate, HO ₂ CCO ₂ H (oxalic acid) and HO ₂ CCO ₂ H hydrate, NaBH ₄ (sodium borohydride) and NaBH ₄ aqueous solution Redox flow battery electrolyte production method characterized in that. The method according to any one of claims 1 to 3, Redox flow battery electrolyte production method characterized in that the addition ratio of the reducing agent is added in a molar ratio of 0.01 to 10 mol relative to the vanadium compound. VOSO ₄ added H ₂ SO ₄ redox flow battery electrolyte prepared by the method of claim 1, Redox flow battery electrolyte, characterized in that the vanadium concentration is 0.001M ~ 10M, H ₂ SO ₄ concentration is 0.001M ~ 16M. The H ₃ PO ₄ redox flow battery electrolyte added with VOHPO ₄ prepared by the method of claim 1, Vanadium concentration is 0.001M ~ 10M, H ₃ PO ₄ concentration is a redox flow battery electrolyte, characterized in that 0.001M ~ 12M. In a redox flow battery, H ₂ SO ₄ to which VOSO ₄ having the composition of claim 7 is added by the method of claim 1 to 6 or H ₃ PO ₄ to which VOHPO ₄ having the composition of claim 8 is added to the method of claim 1 to 6, Redox flow battery, characterized in that used as the electrolyte of the positive electrode, the negative electrode, the positive electrode and the negative electrode. In a redox flow battery, H ₂ SO ₄ to which VOSO ₄ having the composition of claim 7 is added by the method of claim 1 to 6 or H ₃ PO ₄ to which VOHPO ₄ having the composition of claim 8 is added to the method of claim 1 to 6, Redox flow battery, characterized in that used as an electrolytic solution of the cathode or anode and cathode after electrolytic reduction.

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