KR101990516B1 - Method for rebalancing electrolyte of flow battery - Google Patents

Abstract

TECHNICAL FIELD [0001] The present invention relates to a method for regenerating an electrolyte of a flow battery.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a method of regenerating an electrolyte,

TECHNICAL FIELD [0001] The present invention relates to a method for regenerating an electrolyte of a flow battery.

Power storage technology is an important technology for efficient use of energy, such as efficient use of power, improvement of power supply system's ability and reliability, expansion of new and renewable energy with a large fluctuation over time, energy recovery of mobile body, There is a growing demand for possibilities and social contributions.

The supply and demand balances of semi-autonomous regional electricity supply systems such as micro grid and the uneven output of renewable energy such as wind power and solar power are appropriately distributed and voltage and frequency fluctuations Researches on secondary batteries have been actively conducted to control the influence of secondary batteries, and expectations for utilization of secondary batteries are increasing in these fields.

The characteristics required for secondary batteries to be used for large-capacity power storage must be high in energy storage density, and a secondary battery with high capacity and high efficiency most suitable for such characteristics is the most popular.

The flow cell is configured such that the electrodes of the cathode and the anode are positioned on both sides of the separation membrane.

A bipolar plate for electric conduction is provided on the outside of the electrode, and a cathode tank and an anode tank for holding the electrolyte, and an inlet through which the electrolyte enters and an outlet through which the electrolyte again flows.

Korean Patent Publication No. 10-2009-0046087

The present specification is intended to provide a method for regenerating an electrolyte of a flow battery.

The anode includes a cathode, a separator provided between the anode and the cathode, an anode electrolytic solution reservoir for supplying an anode electrolytic solution to the anode and storing an anode electrolytic solution discharged from the anode, and a cathode electrolytic solution supplied to the cathode, And a cathode electrolytic solution storage unit for storing the cathode electrolytic solution discharged from the cathode electrolytic solution storage unit; and stopping the operation of the flow battery after repeating the operation of charging and discharging the flow battery including the cathode electrolytic solution storage unit. Comparing the amount of the anode electrolyte stored in the anode electrolyte storage part with the amount of the cathode electrolyte stored in the cathode electrolyte storage part and injecting the reducing agent into the cathode electrolyte storage part when the amount of the cathode electrolyte is larger than the amount of the anode electrolyte, A first processing step of exposing the anode electrolyte of the anode electrolyte reservoir to oxygen when the amount of the anode electrolyte is greater than the amount of the cathode electrolyte; After the first treatment step, the difference between the amount of the anode electrolyte stored in the anode electrolyte reservoir and the amount of the cathode electrolyte stored in the cathode electrolyte reservoir is 2/5 of the difference between the amount of the anode electrolyte stored in the anode electrolyte reservoir and the amount of electrolyte, To 3/5 of the electrolytic solution; A reducing agent is added to the cathode electrolyte storage part when the electrolyte solution storage part is additionally added to the cathode electrolyte solution storage part, and when the electrolyte solution is further added to the anode electrolyte solution storage part, the anode electrolyte solution in the anode electrolyte solution storage part is exposed to oxygen ; And a mixing and branching step of mixing the cathode electrolytic solution and the anode electrolytic solution after mixing the cathode electrolytic solution and the anode electrolytic solution into the cathode electrolytic solution storage part and the anode electrolytic solution storage part, respectively, .

The present invention has the advantage of recovering the capacity of the battery by regenerating the electrolyte which is deteriorated due to the membrane permeation phenomenon.

The present specification has an advantage in that the degree of ion imbalance of the electrolytic solution is large and the battery capacity can be restored.

The electrolytic solution regeneration method of the present invention is advantageous in that there is no discharged electrolyte in the regeneration process.

Fig. 1 shows the UV-Vis. It is the result of analysis of oxidation number by spectroscopy.
Fig. 2 shows the results of evaluating the cell performance of Experimental Example 2. Fig.

Hereinafter, the present invention will be described in detail.

The present disclosure relates to an anode; Cathode; A separator provided between the anode and the cathode; An anode electrolytic solution storage unit for supplying the anode electrolytic solution to the anode and storing the anode electrolytic solution discharged from the anode; And a cathode electrolytic solution storage part for supplying the cathode electrolytic solution to the cathode and storing the cathode electrolytic solution discharged from the cathode.

The material of the separation membrane is not particularly limited as long as it is capable of transferring ions, and can be selected generally used in the art.

The separation membrane may include a polymer having ion conductivity. The separation membrane may be formed of a polymer having ion conductivity, or may be provided with a polymer having ion conductivity in pores of the porous body.

The polymer having ion conductivity is not particularly limited as long as it is a substance capable of ion exchange, and those generally used in the art can be used.

The ion-conducting polymer may be a hydrocarbon-based polymer, a partially fluorinated polymer, or a fluorinated polymer.

The hydrocarbon-based polymer may be a hydrocarbon-based sulfonated polymer having no fluorine group. Alternatively, the fluorinated polymer may be a sulfonated polymer saturated with a fluorine group, and the partially fluorinated polymer may be a sulfonated polymer that is not saturated with a fluorine group have.

The polymer having ionic conductivity may be at least one selected from the group consisting of perfluorosulfonic acid polymer, hydrocarbon polymer, aromatic sulfon polymer, aromatic ketone polymer, polybenzimidazole polymer, polystyrene polymer, polyester polymer, polyimide polymer, polyvinyl Based polymers, polyether sulfone-based polymers, polyphenylene sulfide-based polymers, polyphenylene oxide-based polymers, polyphosphazene-based polymers, polyethylene naphthalate-based polymers, polyester-based polymers, doped polybenzimidazole-based polymers And may be one or two or more polymers selected from the group consisting of polymers, polyether ketone polymers, polyphenylquinoxaline polymers, polysulfone polymers, polypyrrole polymers and polyaniline polymers. The polymer may be a single copolymer, an alternating copolymer, a random copolymer, a block copolymer, a multi-block copolymer or a graft copolymer, but is not limited thereto.

The ionic conductor may be a polymer having cationic conductivity, for example, Nafion, sulfonated polyetheretherketone (sPEEK) sulfonated polyetherketone (sPEK), polyvinyl (Vinylidene fluoride) -graft-poly (styrene sulfonic acid), PVDF-g-PSSA) and sulphated poly (fluorenyl ether ketone) And may include at least one.

If the porous body includes a plurality of pores, the structure and material of the body are not particularly limited, and those generally used in the art can be used.

For example, the porous body may be formed of a material selected from the group consisting of polyimide (PI), nylon, polyethylene terephthalate (PET), polytetrafluoroethylene (PTFE), polyethylene (PE) polypropylene (PP), poly (arylene ether sulfone) (PAES), and polyetheretherketone (PEEK).

The thickness of the separation membrane may be 20 탆 or more and 200 탆 or less, but is not limited thereto.

The flow battery includes a cathode and an anode separated by a separator.

The cathode is an electrode that receives electrons when it is discharged and is reduced. On the other hand, when the battery is charged, the cathode active material may oxidize and serve as an anode (an oxidizing electrode) for emitting electrons.

The anode refers to an electrode that is oxidized to discharge electrons when it is discharged. On the other hand, when the battery is charged, the anode can function as a cathode (reduction electrode) that is reduced by receiving electrons.

The flow battery includes an anode storage unit and a cathode storage unit, respectively, for storing the anode electrolyte or the cathode electrolyte; A pump connected to the anode reservoir and the cathode reservoir to supply the electrolyte solution to the anode or the cathode; An anode inlet and a cathode inlet through which the anode electrolytic solution or the cathode electrolytic solution flows respectively from the pump; And an anode outlet and an anode outlet through which the electrolyte solution is discharged from the anode or the cathode to the anode reservoir and the cathode reservoir, respectively.

The cathode and the anode each include a current collector; And a porous carbon such as carbon felt provided between the current collector and the separator, wherein the cathode electrolyte is injected and discharged from the cathode storage part, and the anode is chemically and chemically oxidized while being injected and discharged from the anode storage part To discharge the electric energy.

The cathode electrolytic solution and the anode electrolytic solution may each contain a solvent and a cationic metal salt.

The cathode electrolytic solution and the anode electrolytic solution may each further include a cationic metal salt. The cationic metal salt means a salt dissociated into a metal cation while being dissolved in a solvent. At this time, the metal cation acts as an electrode active material.

The cationic metal salt may include at least one of a nitrate of a cationic metal, a chloride salt of a cationic metal, a sulfate of a cationic metal, a sulfate of a cationic metal, and a carbonate of a cationic metal.

Wherein the cationic metal salt is selected from the group consisting of nitrates of vanadium, titanium, chromium, manganese, iron, niobium, molybdenum, silver, tantalum or tungsten; Salts of vanadium, titanium, chromium, manganese, iron, niobium, molybdenum, silver, tantalum or tungsten; A sulfur flame of vanadium, titanium, chromium, manganese, iron, niobium, molybdenum, silver, tantalum or tungsten; Sulphates of vanadium, titanium, chromium, manganese, iron, niobium, molybdenum, silver, tantalum or tungsten; And at least one of vanadium, titanium, chromium, manganese, iron, niobium, molybdenum, silver, tantalum or tungsten carbonate.

When the anode electrolyte contains a cationic metal salt, the molarity of the cationic metal salt in the anode electrolyte may be 0.001 M or more and 0.1 M or less. In other words, the number of moles of the cationic metal salt dissolved in one liter of the anode electrolyte can be 0.001 mol or more and 0.1 mol or less.

When the cathode electrolyte contains a cationic metal salt, the molar concentration of the cationic metal salt in the cathode electrolyte may be 0.001 M or more and 0.1 M or less. In other words, the number of moles of the cationic metal salt dissolved in 1 liter of the cathode electrolyte may be 0.001 mol or more and 0.1 mol or less.

The cathode electrolytic solution and the anode electrolytic solution may include a cathode active material and an anode active material, respectively, as an electrode active material. The cathode active material refers to a material which is reduced by receiving electrons upon discharge and oxidized to form electrons when it is charged. The anode active material refers to a material that is oxidized at the time of discharge to reduce electrons by discharging electrons. The cathode active material and the anode active material may be metal ions dissociated from the cationic metal salt, respectively.

The electrode active material of the flow battery may be a metal ion having three or more types in which the same metal is different in oxidation number. Specifically, the electrode active material of the flow battery may be any one of a vanadium ion, a titanium ion, a chromium ion, a manganese ion, an iron ion, a niobium ion, a molybdenum ion, a silver ion, a tantalum ion and a tungsten ion.

When the electrode active material of the flow battery is vanadium ion, the cathode electrolyte may include at least one of V ^{5 +} and V ^{4 +} , and the anode electrolyte may include at least one of V ^{2 +} and V ^{3 +} . In theory, the vanadium flow battery has an ion balance of an average oxidation number of 3.5. Specifically, in the fully charged state (SOC 100) of the flow battery, the cathode electrolyte contains V ^{5 +} , and the anode electrolyte is V ^{2 +} , And in the fully discharged state (SOC 0) of the flow battery, the cathode electrolyte contains V ^{4 +} , and the anode electrolyte may include V ^{3 +} .

The solvent is not particularly limited as long as it can dissolve the electrode active material. For example, the solvent may include an aqueous sulfuric acid solution, an aqueous hydrochloric acid solution, an aqueous nitric acid solution, and a mixed solution thereof.

The molar concentration of the acid in the sulfuric acid aqueous solution, hydrochloric acid aqueous solution, nitric acid aqueous solution, or mixed solution thereof may be 1 M or more and 6 M or less. In other words, the mole number of the acid in one liter of the electrolytic solution may be 1 mol or more and 6 mol or less. In this case, the acid means sulfuric acid, hydrochloric acid, nitric acid or a mixture thereof. The sulfuric acid aqueous solution, the hydrochloric acid aqueous solution, the nitric acid aqueous solution, or the mixed solution thereof means sulfuric acid, hydrochloric acid, nitric acid or a mixture thereof added to distilled water.

The flow battery may be classified according to the type of the metal ion used as the electrode active material, and the flow battery is not particularly limited as long as the flow battery uses metal ions having three or more types of the same metal as the electrode active material.

The flow battery may be a vanadium flow battery. Specifically, the flow battery may be a vanadium flow battery in which the cathode electrolytic solution contains at least one of V ^{5 +} and V ^{4 +} , and the anode electrolytic solution includes at least one of V ^{2 +} and V ^{3 +} .

The shape of the flow battery is not limited, and may be, for example, a coin, a flat plate, a cylinder, a horn, a button, a sheet or a laminate.

The present specification provides a battery module including the flow battery as a unit cell.

The battery module may be formed by stacking a bipolar plate between the flow batteries of the present specification.

The battery module may be specifically used as a power source for an electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, or a power storage device.

While the flow battery is repeatedly operated to charge and discharge, a crossover phenomenon may occur in which electrode active materials and solvents contained in the electrolyte permeate through the separator and permeate through the separator to the opposite electrode at any one of the electrodes. In this case, the ion concentration and balance of the redox ion species between both electrodes are collapsed, so that the battery capacity and efficiency are lowered.

For example, in the case of a vanadium flow battery, since the rate at which V ^{2 +} and V ^{3 +} of the anode electrolytic solution permeate the separating membrane is higher than V ^{5 +} and V ^{4 + of the} cathode electrolytic solution, The concentration of vanadium ions and the volume of the cathode electrolyte may increase. This tendency is dominant in the case of using a cation separator, and conversely, the concentration of the vanadium ion in the anode electrolyte and the volume of the cathode electrolyte may increase depending on the operating conditions of the battery, the environment, and the use of the anion separator.

TECHNICAL FIELD The present invention relates to a method for regenerating an electrolyte solution in a flow battery that regenerates ion imbalance of redox ion species between both electrodes due to crossover.

The anode includes a cathode, a separator provided between the anode and the cathode, an anode electrolytic solution reservoir for supplying an anode electrolytic solution to the anode and storing an anode electrolytic solution discharged from the anode, and a cathode electrolytic solution supplied to the cathode, And a cathode electrolytic solution storage unit for storing the cathode electrolytic solution discharged from the cathode electrolytic solution storage unit; and stopping the operation of the flow battery after repeating the operation of charging and discharging the flow battery including the cathode electrolytic solution storage unit.

Comparing the amount of the anode electrolyte stored in the anode electrolyte storage part with the amount of the cathode electrolyte stored in the cathode electrolyte storage part and injecting the reducing agent into the cathode electrolyte storage part when the amount of the cathode electrolyte is larger than the amount of the anode electrolyte, A first processing step of exposing the anode electrolyte of the anode electrolyte reservoir to oxygen when the amount of the anode electrolyte is greater than the amount of the cathode electrolyte;

After the first treatment step, the difference between the amount of the anode electrolyte stored in the anode electrolyte reservoir and the amount of the cathode electrolyte stored in the cathode electrolyte reservoir is 2/5 of the difference between the amount of the anode electrolyte stored in the anode electrolyte reservoir and the amount of electrolyte, To 3/5 of the electrolytic solution;

A reducing agent is added to the cathode electrolyte storage part when the electrolyte solution storage part is additionally added to the cathode electrolyte solution storage part, and when the electrolyte solution is further added to the anode electrolyte solution storage part, the anode electrolyte solution in the anode electrolyte solution storage part is exposed to oxygen ; And

And a mixing and branching step of mixing the cathode electrolytic solution and the anode electrolytic solution after mixing the cathode electrolytic solution and the anode electrolytic solution into the cathode electrolytic solution storage part and the anode electrolytic solution storage part, respectively, after the second processing step, to provide.

The method for regenerating the electrolyte of the flow battery may include stopping the operation of the flow battery that has been operated by repeated charging and discharging.

The step of stopping the flow battery is a step of stopping the operation of the flow battery which is operated by repeating charging and discharging several times. Specifically, when the capacity of the flow battery is decreased by 30% or more of the initial discharge capacity (mAh) Stopping the operation. That is, the step of stopping the flow battery may be a step of repeating charging and discharging several times to stop the operation of the flow battery in which the ion unbalance between the electrolytic solutions due to the crossover occurs.

If the amount of the anode electrolyte stored in the anode electrolyte storage portion is larger than the amount of the anode electrolyte stored in the anode electrolyte storage portion when the flow battery is stopped by operating the flow battery repeatedly by repeatedly charging and discharging in the step of stopping the flow battery, Half of the difference in the amount of the cathode electrolyte stored in the electrolyte reservoir should be less than or equal to the amount of the divalent vanadium in the anode electrolyte.

If the amount of the anode electrolyte stored in the anode electrolyte storage portion is larger than the amount of the anode electrolyte stored in the anode electrolyte storage portion when the operation of the flow battery which is operated by repeating charging and discharging several times in the step of stopping the flow battery is stopped, Half of the difference in the amount of the cathode electrolyte stored in the electrolyte reservoir should be less than or equal to the amount of pentavalent vanadium in the cathode electrolyte.

The step of stopping the flow battery may stop the operation of the flow battery, which was operated by repeating charging and discharging several times, in a fully charged state (SOC 100).

For example, the fully charged state (SOC 100) of the vanadium flow battery is, theoretically, the cathode electrolyte contains V ^{5 +} , and the anode electrolyte contains V ^{2 +} . When the cathode electrolytic solution is in an unbalanced state with a relatively large amount, in the fully charged state, the anode electrolytic solution contains only V ^{2+. However} , in the cathode electrolytic solution, vanadium ions of the anode electrolytic solution pass through the separator to V ⁵⁺ of the cathode electrolytic solution to provide an electronic part V ⁵⁺ is oxidized to V ⁴⁺ may be present in the V ⁴⁺ and V ⁵⁺ together. On the other hand, if the anode electrolyte is in a relatively unstable ion-unbalanced state, the cathode electrolytic solution contains only V ^{5 +} in a fully charged state, but the anode electrolyte is a solution in which vanadium ions in the cathode electrolytic solution permeate V ² whereby the electronic part of the ⁺ V ²⁺ is reduced to V ³⁺ may be present in the V ^{+ 3} V with a ^2+.

The method for regenerating the electrolyte of the flow battery includes comparing the amount of the anode electrolyte stored in the anode electrolyte storage part with the amount of the cathode electrolyte stored in the cathode electrolyte storage part and when the amount of the cathode electrolyte is greater than the amount of the anode electrolyte, And a first processing step of supplying a reducing agent to the storage part and exposing the anode electrolyte of the anode electrolyte storage part to oxygen when the amount of the anode electrolyte is larger than the amount of the cathode electrolyte.

The reducing agent in the first treatment step may comprise hydrazine monohydrate (N ₂ H ₄ -H ₂ O). The 1 mol of the hydrazine monohydrate produces N ₂ , H ₂ O and H ₂ SO ₄ as the intermediate and final products of the reduction reaction and provides four electrons (4e ^- ) to the pentavalent vanadium so that 1 mol of hydrazine monohydrate VO ₂ ⁺ equivalent to 4 moles can be reduced to VO ^{2 +} . That is, since hydrazine monohydrate produces a gas that easily generates a substance already present in the electrolytic solution or can easily be removed, there is little or no impurity in the electrolyte after reduction, and the efficiency is high because one mole of hydrazine monohydrate reduces 4 moles of vanadium.

When the flow battery is a vanadium flow battery, the input amount of hydrazine monohydrate as a reducing agent in the first treatment step is 0.25 mol based on 1 mol of the pentavalent vanadium contained in the cathode electrolyte, but considering the reaction heat and the reaction rate And may be adjusted in the range of 0.2 mole to 0.3 mole.

In the first processing step, when the anode electrolyte of the anode electrolyte storage portion is exposed to oxygen, the anode electrolyte storage portion can be exposed to air in the atmosphere containing oxygen or oxygen or oxygen containing high purity.

In the first processing step, the time for exposing the anode electrolyte of the anode electrolyte storage part to oxygen may be changed depending on whether the electrolyte solution is stirred, the oxygen concentration of the exposed gas containing oxygen, the electrolyte capacity, and the shape of the electrolyte storage container.

Oxidation of the metal ions in the anode electrolyte can be accomplished through the measurement of a UV-VIS spectrophotometer or open circuit voltage (OCV). For example, if the OCV value reaches a level similar to the OCV in the initial discharge state, it can be considered that the oxidation is completed.

The method for regenerating an electrolyte solution for a flow battery according to claim 1, wherein, after the first treatment step, the amount of the anode electrolyte stored in the anode electrolyte storage part and the amount of the cathode electrolyte stored in the cathode electrolyte storage part To 3/5 of the difference in the amount of the electrolytic solution.

In the method for regenerating the electrolyte of the flow battery, after the first processing step, if the amount of the cathode electrolyte is large, the cathode electrolyte through the first processing step may be transferred from the cathode electrolyte storage to the anode electrolyte storage. At this time, the amount of the cathode electrolytic solution transferred from the cathode electrolytic solution storage portion to the anode electrolytic solution storage portion is adjusted so that the amount of the anode electrolytic solution stored in the anode electrolytic solution storage portion and the amount of the anode electrolytic solution stored in the cathode electrolytic solution storage portion The cathode electrolytic solution of 2/5 to 3/5 of the difference in the amount of the cathode electrolytic solution can be transferred.

In the method for regenerating the electrolyte of the flow battery, after the first processing step, if the amount of the cathode electrolyte is large, the cathode electrolyte through the first processing step may be transferred from the cathode electrolyte storage to the anode electrolyte storage. At this time, the amount of the cathode electrolytic solution transferred from the cathode electrolytic solution storage portion to the anode electrolytic solution storage portion is adjusted so that the amount of the anode electrolytic solution stored in the anode electrolytic solution storage portion and the amount of the anode electrolytic solution stored in the cathode electrolytic solution storage portion The cathode electrolytic solution of half the difference in the amount of the cathode electrolytic solution can be transferred.

In the method for regenerating the electrolyte of the flow battery, after the first processing step, if the amount of the anode electrolyte is large, the anode electrolyte can be transferred from the anode electrolyte reservoir to the cathode electrolyte reservoir through the first processing step. At this time, the amount of the anode electrolytic solution transferred from the anode electrolytic solution storage portion to the cathode electrolytic solution storage portion is adjusted so that the amount of the anode electrolytic solution stored in the anode electrolytic solution storage portion and the amount of the anode electrolytic solution stored in the cathode electrolytic solution storage portion The anode electrolyte of 2/5 to 3/5 of the difference in the amount of the cathode electrolyte can be transferred.

In the method for regenerating the electrolyte of the flow battery, after the first processing step, if the amount of the anode electrolyte is large, the anode electrolyte can be transferred from the anode electrolyte reservoir to the cathode electrolyte reservoir through the first processing step. At this time, the amount of the anode electrolytic solution transferred from the anode electrolytic solution storage portion to the cathode electrolytic solution storage portion is adjusted so that the amount of the anode electrolytic solution stored in the anode electrolytic solution storage portion and the amount of the anode electrolytic solution stored in the cathode electrolytic solution storage portion It is possible to transfer the anode electrolyte half of the difference in the amount of the cathode electrolyte.

The method for regenerating the electrolyte of the flow battery may further include the step of injecting a reducing agent into the cathode electrolyte reservoir when the electrolytic solution is additionally added to the cathode electrolyte reservoir and when the electrolyte is further added to the anode electrolyte reservoir, And a second processing step of exposing the anode electrolyte of the storage portion to oxygen.

The reducing agent in the second treatment step may comprise hydrazine monohydrate (N ₂ H ₄ -H ₂ O). The 1 mol of the hydrazine monohydrate produces N ₂ , H ₂ O and H ₂ SO ₄ as the intermediate and final products of the reduction reaction and provides four electrons (4e ^- ) to the pentavalent vanadium so that 1 mol of hydrazine monohydrate VO ₂ ⁺ equivalent to 4 moles can be reduced to VO ^{2 +} . That is, since hydrazine monohydrate produces a gas that easily generates a substance already present in the electrolytic solution or can easily be removed, there is little or no impurity in the electrolyte after reduction, and the efficiency is high because one mole of hydrazine monohydrate reduces 4 moles of vanadium.

When the flow battery is a vanadium flow battery, the amount of reducing agent is determined according to the amount of vanadium pentavalent contained in the cathode electrolytic solution storing portion, and the amount of vanadium pentavalent is measured by measuring an open circuit voltage (OCV) Can be inferred.

When the flow battery is a vanadium flow battery, the amount of hydrazine monohydrate as a reducing agent in the second treatment step is 0.25 mol based on 1 mol of the pentavalent vanadium contained in the cathode electrolyte, but considering the reaction heat and the reaction rate And may be adjusted in the range of 0.2 mole to 0.3 mole.

In the second processing step, when the anode electrolyte of the anode electrolyte storage portion is exposed to oxygen, the anode electrolyte storage portion can be exposed to air in the atmosphere containing oxygen or oxygen or oxygen containing high purity.

In the second processing step, the time for exposing the anode electrolyte of the anode electrolyte storage part to oxygen may be changed depending on whether the electrolyte solution is stirred, the oxygen concentration of the exposed gas containing oxygen, the electrolyte capacity, and the shape of the electrolyte storage container.

Oxidation of the metal ions in the anode electrolyte can be accomplished through the measurement of a UV-VIS spectrophotometer or open circuit voltage (OCV). For example, if the OCV value reaches a level similar to the OCV in the initial discharge state, it can be considered that the oxidation is completed.

The method for regenerating the electrolyte solution of the flow battery may further include separately stirring the cathode electrolyte in the cathode electrolyte storage and the anode electrolyte in the anode electrolyte reservoir before or after each step. In this case, the reaction of the electrolytic solution can proceed uniformly and rapidly during the reaction of each step, and the electrolytic solution can be kept in a uniform state before performing the next step after each step.

The method for regenerating the electrolyte of the flow battery includes a mixing and branching step of mixing the cathode electrolytic solution and the anode electrolytic solution after the second processing step and then mixing the mixed electrolyte into the cathode electrolytic solution storage part and the anode electrolytic solution storage part can do.

After the second treatment step, the anode electrolyte ³ comprises only V ⁺ and the cathode, and the electrolyte contains only V ^{+ 4,} the case of mixing of these anode electrolyte and cathode electrolyte anode in a state of maintaining the V ^{3 +} and V ⁴⁺ electrolyte And the cathode electrolyte. This is because V ^{3 +} and V ^{4 +} present in the electrolyte are in a state in which electrons can not be given or received with respect to each other, so that V ^{3 +} and V ^{4 +} can be maintained without electron migration.

Since the hydrogen ions are consumed by the reducing agent introduced in the first treatment step or the second treatment step and water is generated, the concentration of hydrogen ions in the anode electrolytic solution and the cathode electrolytic solution and the amount of water can be adjusted through the mixing and branching steps have.

The method for regenerating an electrolyte of a flow battery includes the steps of adding an acid to at least one of a cathode electrolyte storage and an anode electrolyte storage before the mixing and branching steps; Adding the acid to the mixed solution of the cathode electrolyte and the anode electrolyte before the cathode electrolyte and the anode electrolyte are mixed with each other in the mixing and branching steps and then divided into the cathode electrolyte storage part and the anode electrolyte storage part; Or adding the acid to the cathode electrolyte storage and the anode electrolyte storage after the mixing and the branching step.

Since the hydrogen ion is consumed by the reducing agent injected in the first treatment step or the second treatment step, the amount of consumed hydrogen ions can be recovered through the addition of the acid.

In the addition step of the acid, the addition amount of the acid can be determined by the amount of the reducing agent introduced in the first treatment step or the second treatment step. When hydrazine monohydrate is used as the reducing agent introduced in the first treatment step or the second treatment step, an acid four times as much as the amount of the added reducing agent can be added. Specifically, 4 moles of acid may be added per mole of the charged hydrazine monohydrate.

The acid may be sulfuric acid, hydrochloric acid, nitric acid, or a mixture thereof, and it is preferable to add the same acid as the kind of acid contained in the electrolytic solution before regeneration.

The method for regenerating the electrolyte of the flow battery may include the steps of applying negative pressure to the cathode electrolyte storage and the anode electrolyte reservoir after the mixing and branching steps or applying negative pressure to the inside of the cathode electrolyte reservoir and the anode electrolyte reservoir, And filling the space except the space with an inert gas.

The method for regenerating the electrolyte of the flow battery may further include the step of reactivating the flow battery after the mixing and the branching step. Specifically, the metal ions included in the electrolytic solution after the mixing and the branching step are in a state where metal ions in a completely discharged state are mixed with each other. Therefore, the step of reactivating the flow battery may include charging the flow battery first, May be repeatedly operated.

When the flow battery is a vanadium battery, since the metal ions included in the electrolyte after the mixing and the branching are in a state where V ^{4 +} and V ^{3 +} in a fully discharged state are mixed with each other, The flow battery may be charged first and then discharged and charged repeatedly.

One embodiment of the present invention relates to a fuel cell including an anode, a cathode, a separator provided between the anode and the cathode, an anode electrolyte storage portion for storing the anode electrolyte discharged from the anode by supplying the anode electrolyte with the anode, And a cathode electrolytic solution storage unit for storing the cathode electrolytic solution discharged from the cathode, and stopping the operation of the flow battery after repeating the operation of charging and discharging the flow battery.

A first treatment step of injecting a reducing agent into the cathode electrolyte storage part;

Transferring an electrolyte solution from the cathode electrolytic solution to an anode electrolytic solution in an amount equal to the difference between the amount of the anode electrolytic solution stored in the anode electrolytic solution storage part and the amount of the cathode electrolytic solution stored in the cathode electrolytic solution storage part after the first processing step;

A second treatment step of exposing the anode electrolyte of the anode electrolyte storage part to which oxygen is additionally added, to oxygen; And

And a mixing and branching step of mixing the cathode electrolytic solution and the anode electrolytic solution after mixing the cathode electrolytic solution and the anode electrolytic solution into the cathode electrolytic solution storage part and the anode electrolytic solution storage part, respectively, after the second processing step, to provide.

Another embodiment of the present invention relates to a fuel cell including an anode, a cathode, a separator provided between the anode and the cathode, an anode electrolyte reservoir for storing the anode electrolyte discharged from the anode by supplying the anode electrolyte with the anode, And a cathode electrolytic solution storage unit for storing the cathode electrolytic solution discharged from the cathode, and stopping the operation of the flow battery after repeating the operation of charging and discharging the flow battery.

A first processing step of exposing the anode electrolyte of the anode electrolyte storage part to oxygen;

After the first treatment step, transferring half of the electrolyte solution from the anode electrolytic solution to the cathode electrolytic solution, the difference between the amount of the anode electrolytic solution stored in the anode electrolytic solution storage part and the amount of the cathode electrolytic solution stored in the cathode electrolytic solution storage part;

A second treatment step of injecting a reducing agent into the cathode electrolyte storage part to which the electrolyte is further added; And

And a mixing and branching step of mixing the cathode electrolytic solution and the anode electrolytic solution after mixing the cathode electrolytic solution and the anode electrolytic solution into the cathode electrolytic solution storage part and the anode electrolytic solution storage part, respectively, after the second processing step, to provide.

Hereinafter, the present invention will be described in more detail by way of examples. However, the following embodiments are intended to illustrate the present disclosure and are not intended to limit the present disclosure.

[Example]

[Example 1]

An electrolyte solution in which 1 M VOSO ₄ was dissolved in an aqueous solution of 3M sulfuric acid was used in an amount of 50 ml per each electrode. If the vanadium oxidation state is the anode of the electrolytic solution was V ^{+ 2,} when the cathode was the V ^{5 +,} V ²⁺ electrolytic solution was treated in a N ₂ atmosphere.

[Example 2]

In order to forcibly pollute the cathode electrolytic solution with the assumption that the water of the anode electrolytic solution and the vanadium ion permeate the separator membrane, 20 ml of V ^{3 +} electrolytic solution is added to the cathode electrolytic solution of Example 1, theoretically, V ^{4 +40} ml and V ^{5 +} 30 ml 70 ml of a vanadium mixed ionic electrolytic solution was prepared.

0.45 g of hydrazine monohydrate (N ₂ H ₄ -H ₂ O) was added to the mixed electrolytic solution of vanadium at a time while stirring with magnetic bar and stirred for 5 minutes to prepare a cathode electrolytic solution reduced to V ^{4 +} .

30 ml of the V ^{2 +} anode electrolytic solution of Example 1 was prepared, 20 ml of the cathode electrolytic solution reduced to V ^{4 +} was taken, mixed with 30 ml of the V ^{2 +} anode electrolytic solution, and stirred in the air for 30 minutes.

Thereafter, 50 ml of the finally prepared anode electrolytic solution and 50 ml of the cathode electrolytic solution were thoroughly mixed to obtain a vanadium electrolytic solution having an average oxidation number of 3.5 of 100 ml. The mixture was further divided into 1: 1 portions and transferred to the respective electrolyte storage portions.

[Example 3]

25 ml of V ^{3 +} electrolytic solution was theoretically added to the cathode electrolyte of Example 1 in order to forcibly pollute the cathode electrolytic solution, assuming that the water of the anode electrolytic solution and the vanadium ion permeated the separator membrane. Theoretically, V ^{4 +50} ml and V ^{5 +} 25 ml 75 ml of a vanadium mixed ionic electrolytic solution was prepared.

0.39 g of hydrazine monohydrate (N ₂ H ₄ -H ₂ O) was added to the mixed electrolytic solution of vanadium at the same time with magnetic bar stirring and stirred for 5 minutes to prepare a cathode electrolytic solution reduced to V ^{4 +} .

25 ml of the V ^{2 +} anode electrolytic solution of Example 1 was prepared, 25 ml of the cathode electrolyte reduced to V ^{4 +} was taken, mixed with 25 ml of the V ^{2 +} anode electrolyte, and stirred in the air for 30 minutes.

Thereafter, 50 ml of the finally prepared anode electrolytic solution and 50 ml of the cathode electrolytic solution were thoroughly mixed to obtain a vanadium electrolytic solution having an average oxidation number of 3.5 of 100 ml. The mixture was further divided into 1: 1 portions and transferred to the respective electrolyte storage portions.

[Experimental Example 1]

vanadium Oxidation number  analysis

Based on the pure V ⁴⁺ cathode electrolyte, 1 ml of the V ⁴⁺ cathode electrolyte recovered in Examples 2 and 3 was taken and subjected to vanadium oxidation analysis using a UV-Vis spectrophotometer.

As a result, it can be seen that an absorption peak due to V ⁴⁺ ion occurs at around 790 nm as shown in FIG. 1, and the reference electrolyte having a peak of V ^{4 +} cathode electrolyte regenerated in Examples 2 and 3 is composed of pure V ⁴⁺ (Ref. V ⁴⁺ ).

[Experimental Example 2]

The electrolyte was supplied / circulated to each electrode at a flow rate of 25 ml / min in a volume of 50 ml. The electrode was a carbon felt having a size of 5 x 5 cm. The battery was rated at a current rate of 50 mA / cm ² and an operating voltage of 0.8 V to 1.7 V And the results are shown in Fig. 2 (discharge capacity) and Fig. 3 (efficiency).

2 and 3, the regenerated electrolytic solution of Examples 2 and 3 exhibited a lower performance than the initial fresh electrolytic solution of Example 1, which is equivalent to the evaluation using the reference electrolytic solution because Example 1 is an electrolytic solution without the addition of a reducing agent. Can be seen.

It can be understood that the regenerated electrolytic solution of Examples 2 and 3 is lower in charge / discharge capacity than the fresh electrolytic solution of Example 1, and the performance gap is not so large that the electrolytic solution of Examples 2 and 3 is regenerated at an appropriate level.

Claims (10)

A cathode, an anode, a cathode, a separator provided between the anode and the cathode, an anode electrolyte reservoir for supplying the anode electrolyte with the anode and storing the anode electrolyte discharged from the anode, and a cathode electrolyte supplied to the cathode, Stopping the operation of the flow battery after repeating the operation of charging and discharging the flow battery including the cathode electrolytic solution storing portion for storing the cathode electrolytic solution;
Comparing the amount of the anode electrolyte stored in the anode electrolyte storage part with the amount of the cathode electrolyte stored in the cathode electrolyte storage part and injecting the reducing agent into the cathode electrolyte storage part when the amount of the cathode electrolyte is larger than the amount of the anode electrolyte, A first processing step of exposing the anode electrolyte of the anode electrolyte reservoir to oxygen when the amount of the anode electrolyte is greater than the amount of the cathode electrolyte;
After the first treatment step, the difference between the amount of the anode electrolyte stored in the anode electrolyte reservoir and the amount of the cathode electrolyte stored in the cathode electrolyte reservoir is 2/5 of the difference between the amount of the anode electrolyte stored in the anode electrolyte reservoir and the amount of electrolyte, To 3/5 of the electrolytic solution;
A reducing agent is added to the cathode electrolyte storage part when the electrolyte solution storage part is additionally added to the cathode electrolyte solution storage part, and when the electrolyte solution is further added to the anode electrolyte solution storage part, the anode electrolyte solution in the anode electrolyte solution storage part is exposed to oxygen ; And
And a mixing and branching step of mixing the cathode electrolytic solution and the anode electrolytic solution after the second treatment step and mixing the electrolytic solution into the cathode electrolytic solution storage part and the anode electrolytic solution storage part, respectively. The method of claim 1, wherein the step of transferring the electrolytic solution comprises: a step of transferring the electrolytic solution to the anode electrolytic solution storage unit, Of the electrolytic solution is transferred. The method according to claim 1, wherein the reducing agent in the first treating step and the second treating step comprises hydrazine monohydrate (N ₂ H ₄ -H ₂ O). 2. The method according to claim 1, wherein the electrode active material of the flow battery is a metal ion having three or more types in which the same metal is different in oxidation number. The flow battery according to claim 4, wherein the electrode active material of the flow battery is any one of vanadium ion, titanium ion, chromium ion, manganese ion, iron ion, niobium ion, molybdenum ion, silver ion, tantalum ion and tungsten ion. . The method of claim 1, wherein the cathode electrolyte comprises at least one of V ^{5 +} and V ^{4 +} , and the anode electrolyte comprises at least one of V ^{2 +} and V ^{3 +} . 7. The electrolytic solution regeneration method according to claim 6, wherein the amount of the reducing agent introduced in the first treatment step and the second treatment step is 1: 0.2 to 0.3 based on moles of V ^{5 +} contained in the cathode electrolytic solution. The method as claimed in claim 1, wherein after the mixing and the branching step, a negative pressure is applied to the inside of the cathode electrolyte storage part and the anode electrolyte storage part, a negative pressure is applied to the inside of the cathode electrolyte storage part and the anode electrolyte storage part, And filling the cell with an inert gas. The method according to claim 1, further comprising the step of reactivating the flow battery after the mixing and branching step. The method of claim 1, further comprising: before the mixing and branching step, adding an acid to at least one of the cathode electrolyte storage and the anode electrolyte storage; Adding the acid to the mixed solution of the cathode electrolyte and the anode electrolyte before mixing the cathode electrolyte solution and the anode electrolyte into the cathode electrolyte solution reservoir and the anode electrolyte reservoir in the mixing and branching step; Or adding the acid to the cathode electrolyte storage part and the anode electrolyte storage part after the mixing and the branching step.

Images