Method and apparatus for processing electrolyte solution containing vanadium ions

Abstract

The present invention relates to a method and an apparatus for processing an electrolyte solution containing vanadium ions, and performs a charge reaction, a discharge reaction and a reverse charge reaction so that, in the charge reaction, impurities contained in a first electrolyte solution can be removed and, in the reverse charge reaction, impurities contained in a second electrolyte solution can be removed. Therefore, impurities contained in the electrolyte solution containing vanadium ions can be efficiently removed without repeatedly performing, several times, a charging reaction on the electrolyte solution containing vanadium ions.

Description

Method and device for treating an electrolyte containing vanadium ions

[0001] The present invention relates to a technology for treating impurities in an electrolyte containing vanadium ions. More specifically, the present invention relates to a method and device for removing impurities from an electrolyte containing vanadium ions using an electrochemical reaction.

[0002] Vanadium ion batteries (VIBs) and redox flow batteries (VRFBs) utilize electrolytes containing vanadium ions. Electrolytes containing vanadium ions are aqueous, so they offer high safety against explosions and other risks when applied to secondary batteries, as well as the added benefit of extending battery life. This has led to their continued use until recently. Furthermore, electrolytes containing vanadium ions boast the longest lifespan among oxidation-reduction secondary batteries, are advantageous for increasing capacity, and, because the electrolyte can be separated and reused through the electrochemical reaction of charge and discharge, they offer advantages in terms of cost.

[0003] The electrolyte containing vanadium ions used in the oxidation electrode section (also called the anode section) and the reduction electrode section (also called the cathode section) requires vanadium ions with an oxidation number of 4+ for the oxidation electrode section and 3+ for the reduction electrode section, respectively, based on a fully discharged state, and vanadium ions with an oxidation number of 5+ for the oxidation electrode section and 2+ for the reduction electrode section, based on a fully charged state. The charge / discharge reaction occurs as the oxidation number of the vanadium active material changes, and in order for the electrochemical reversible reaction to occur, it is important to manufacture the electrolyte of the oxidation electrode section and the reduction electrode section so that the oxidation numbers of the vanadium ions are matched.

[0004] In general, as a vanadium ion-containing electrolyte, an electrolyte with a vanadium oxidation number of 3.5 (3.5+) that can be commonly used for the electrolyte supplied to the reduction electrode section and the electrolyte supplied to the oxidation electrode section has been used.

[0005] Meanwhile, if impurities exceed a certain level in an electrolyte containing vanadium ions, side reactions can occur, leading to problems such as reduced performance and lifespan. In particular, batteries using electrolytes containing vanadium ions undergo repeated charging and discharging, which can lead to the continuous accumulation of damage caused by side reactions, potentially leading to fatal problems such as battery failure.

[0006] Furthermore, if a certain level of impurities are present in the vanadium-ion-containing electrolyte, pressure will be generated during the electroreduction process at the reduction electrode. This pressure generation can degrade the life characteristics. Compared to vanadium redox flow batteries, vanadium-ion batteries have a relatively small volume, making it difficult to buffer the pressure generation, making this pressure generation a greater problem in vanadium-ion batteries.

[0007] Among the elements present in the electrolyte containing vanadium ions, impurities such as metals, especially transition elements such as Cr, Mn, Fe, Ni, Cu, Zn, Mo, Pd, Cd, and Pt, can be factors in generating hydrogen.

[0008] Therefore, a technology to remove metal impurities such as transition elements in an electrolyte containing vanadium ions is required.

[0009] Metal impurities can be removed electrochemically. Figure 1 schematically illustrates a typical electrochemical removal method for metal impurities.

[0010] Referring to Figure 1, an electrolyte containing vanadium (V) having an oxidation number of 3.5 is supplied separately to an oxidation electrode section and a reduction electrode section and then supplied to a charging cell. In the oxidation electrode section of the charging cell, an oxidation reaction occurs in which the oxidation number of V ions increases to 5, and in the reduction electrode section of the charging cell, a reduction reaction occurs in which the oxidation number of V ions decreases to 2. In this reduction reaction, metal impurities contained in the electrolyte containing V ions are removed as they are precipitated / adsorbed on the reduction electrode (cathode).

[0011] However, in the method illustrated in Fig. 1, metal impurities are only removed from the reduction electrode of the charging cell, and are not removed from the electrolyte passing through the oxidation electrode. Therefore, to sufficiently remove metal impurities, the vanadium-containing electrolyte must be circulated N times (approximately 4 times or more) to undergo repeated electrochemical reactions.

[0012] The problem to be solved by the present invention is to provide a method for treating a vanadium ion electrolyte capable of effectively removing impurities from the vanadium ion-containing electrolyte.

[0013] The problem to be solved by the present invention is to provide an impurity removal device for a vanadium ion electrolyte that can be used in the above method for treating an electrolyte containing vanadium ions.

[0014] The objects of the present invention are not limited to the purposes mentioned above, and other purposes not mentioned will be clearly understood by those skilled in the art from the description below.

[0015] According to one embodiment of the present invention for solving the above problem, a method for treating a vanadium ion-containing electrolyte comprises the steps of: (a) separating a vanadium ion-containing electrolyte into a first electrolyte and a second electrolyte; (b) oxidizing vanadium ions of the second electrolyte while reducing vanadium ions of the first electrolyte through a first charging reaction; (c) reducing vanadium ions of the second electrolyte while oxidizing vanadium ions of the first electrolyte through a discharge reaction; (d) reducing vanadium ions of the second electrolyte while oxidizing vanadium ions of the first electrolyte through a second charging reaction; and (e) mixing the first electrolyte and the second electrolyte.

[0016] In the step (b), impurities contained in the first electrolyte are removed, and in the step (d), impurities contained in the second electrolyte are removed.

[0017] The above vanadium ion-containing electrolyte may have an oxidation number of 3.5.

[0018] In the step (b), the oxidation number of the vanadium ion of the first electrolyte may be reduced from 3.5 to 2-3, the oxidation number of the vanadium ion of the second electrolyte may be oxidized from 3.5 to 4-5, the oxidation number of the vanadium ion of the first electrolyte may be reduced from 2-3 to 3.5, the oxidation number of the vanadium ion of the second electrolyte may be reduced from 4-5 to 3.5, and the oxidation number of the vanadium ion of the first electrolyte may be oxidized from 3.5 to 4-5, and the oxidation number of the vanadium ion of the second electrolyte may be reduced from 3.5 to 2-3.

[0019] In steps (b) to (d), the flow rates of the first electrolyte and the second electrolyte may be 1.5 L / h or less.

[0020] In the step (b), a voltage of 1.4 V or higher may be applied to a cell (first charging cell) in which the first charging reaction is performed, and in the step (d), a voltage of 1.4 V or higher may be applied to a cell (second charging cell) in which the second charging reaction is performed.

[0021] The same voltage can be applied to the first charging cell, the cell in which the discharge reaction is performed (the discharge cell), and the second charging cell.

[0022] In the above step (c), the discharge cell can be maintained in a short state.

[0023] When the voltage applied to the cell in which the first charging reaction is performed and the cell in which the second charging reaction is performed is A (V), and the flow rates of the first electrolyte and the second electrolyte in steps (b) to (d) are B (L / h), the voltage and flow rate can be adjusted to satisfy the following relationship: 2.1 ≤ 2A - B.

[0024] After the above step (e), a step of supplying a vanadium ion-containing electrolyte to at least one of the first charging cell, the discharge cell, and the second charging cell and then applying a reverse voltage to desorb impurities adsorbed on the electrode into the vanadium ion-containing electrolyte may be additionally included.

[0025] The application of the above reverse voltage can be performed by applying a reverse voltage of 1.4 to 2.1 V for more than 1 minute.

[0026]

[0027] According to one embodiment of the present invention for solving the above problem, a device for processing a vanadium ion-containing electrolyte comprises: a supply line for supplying a vanadium ion-containing electrolyte from an electrolyte storage unit by separating the electrolyte into a first electrolyte and a second electrolyte; a first cell in which a first charging reaction is performed on the first electrolyte and the second electrolyte; a second cell in which a discharge reaction is performed on the first electrolyte and the second electrolyte that have passed through the first cell; a third cell in which a second charging reaction is performed on the first electrolyte and the second electrolyte that have passed through the second cell; and a recovery line for merging the first electrolyte and the second electrolyte that have passed through the third cell and supplying them to the electrolyte storage unit, wherein in the first cell in which the first charging reaction is performed, a reduction electrode unit is arranged to be in contact with the first electrolyte, and in the third cell in which the second charging reaction is performed, a reduction electrode unit is arranged to be in contact with the second electrolyte.

[0028] The first cell may include a first reduction electrode portion supplied with the first electrolyte and a first oxidation electrode portion supplied with the second electrolyte, the second cell may include a second oxidation electrode portion supplied with the first electrolyte from the first reduction electrode portion of the first cell and a second reduction electrode portion supplied with the second electrolyte from the first oxidation electrode portion of the first cell, and the third cell may include a third oxidation electrode portion supplied with the first electrolyte from the second oxidation electrode portion of the second cell and a third reduction electrode portion supplied with the second electrolyte from the second reduction electrode portion of the second cell.

[0029] In the first cell, the oxidation number of the vanadium ion of the first electrolyte may be lowered in the first reduction electrode section through a first charging reaction, and the oxidation number of the vanadium ion of the second electrolyte may be increased in the first oxidation electrode section. In the second cell, the oxidation number of the vanadium ion of the first electrolyte may be increased in the second oxidation electrode section through a discharge reaction, and the oxidation number of the vanadium ion of the second electrolyte may be decreased in the second reduction electrode section. In the third cell, the oxidation number of the vanadium ion of the first electrolyte may be increased in the second oxidation electrode section through a second charging reaction, and the oxidation number of the vanadium ion of the second electrolyte may be decreased in the second reduction electrode section.

[0030] The above electrolyte storage unit can store an electrolyte containing vanadium ions having an oxidation number of 3.5.

[0031] In the first cell, the oxidation number of the vanadium ion of the first electrolyte of the first reduction electrode unit is reduced from 3.5 to 2-3, the oxidation number of the vanadium ion of the second electrolyte of the first oxidation electrode unit is oxidized from 3.5 to 4-5, in the second cell, the oxidation number of the vanadium ion of the first electrolyte of the second oxidation electrode unit is oxidized from 2-3 to 3.5, and the oxidation number of the vanadium ion of the second electrolyte of the second reduction electrode unit is reduced from 4-5 to 3.5, and in the third cell, the oxidation number of the vanadium ion of the first electrolyte of the third oxidation electrode unit is oxidized from 3.5 to 4-5, and the oxidation number of the vanadium ion of the second electrolyte of the third reduction electrode unit can be reduced from 3.5 to 2-3.

[0032] A voltage of 1.4 V or more can be applied to each of the first cell and the third cell.

[0033] The same voltage can be applied to the first cell, the second cell, and the third cell.

[0034] The above second cell may be maintained in a short state.

[0035] When the applied voltage for the first cell and the third cell is A (V), and the flow rates of the first electrolyte and the second electrolyte are B (L / h), the voltage and flow rates can be adjusted to satisfy the following relationship: 2.1 ≤ 2A - B.

[0036] According to the method and device for treating a vanadium ion-containing electrolyte according to the present invention, by performing a charging reaction, a discharging reaction, and a reverse charging reaction, impurities contained in a first electrolyte can be removed in the charging reaction, and impurities contained in a second electrolyte can be removed in the reverse charging reaction. As a result, impurities contained in a vanadium ion-containing electrolyte can be efficiently removed without repeating the charging reaction of the vanadium ion-containing electrolyte multiple times.

[0037] In addition, the impurity removal efficiency can be improved by controlling the voltage applied to the charging reaction cell and the reverse charging reaction cell and the flow rate of the vanadium ion-containing electrolyte.

[0038] In addition, by performing a refresh process using reverse voltage for each cell, the decrease in impurity removal efficiency can be suppressed.

[0039] The effects of the present invention are not limited to the effects mentioned above, and other effects not mentioned will be clearly understood by those skilled in the art from the description of the claims.

[0040] Figure 1 schematically illustrates a general electrochemical removal method for metal impurities.

[0041] Figure 2 schematically illustrates a method for treating a vanadium ion-containing electrolyte according to an embodiment of the present invention.

[0042] Figure 3 schematically illustrates a device for processing a vanadium ion-containing electrolyte according to an embodiment of the present invention.

[0043] Figure 4 shows an example of a device capable of measuring the pressure of a cell.

[0044] Figure 5 shows the pressure measurement results of the examples and comparative examples.

[0045] Figure 6 shows the pressure measurement results of the examples and comparative examples after the refresh process.

[0046] The advantages and features of the present invention, and the methods for achieving them, will become clearer with reference to the embodiments described in detail below together with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below and may be implemented in various different forms. These embodiments are provided only to ensure that the disclosure of the present invention is complete and to fully inform those skilled in the art of the scope of the invention, and the present invention is defined only by the scope of the claims. Like reference numerals designate like elements throughout the specification.

[0047] Throughout this specification, unless otherwise specifically stated, each component may be singular or plural.

[0048] In interpreting the components in this specification, even if there is no separate explicit description, it is interpreted as including the error range.

[0049] When it is described herein that any component is “connected,” “coupled,” or “connected” to another component, it should be understood that the components may be directly connected or connected to one another, but that other components may also be “interposed” between the components, or that each component may be “connected,” “coupled,” or “connected” through another component.

[0050] In this specification, when the terms "includes," "has," "consists of," "arranges," "provides," etc. are used for components, other parts may be added unless "only" is used.

[0051] Unless otherwise specified in this specification, any reference to a unit is interpreted to mean “weight.”

[0052] In this specification, unless otherwise specifically stated, “vanadium ion-containing electrolyte” is interpreted to refer to the same thing as “vanadium ion electrolyte,” “electrolyte using (utilizing) vanadium ions,” “electrolyte containing vanadium ions,” “vanadium electrolyte,” “electrolyte containing vanadium active material,” etc.

[0053] In this specification, the oxidation number of the vanadium ion of the vanadium ion electrolyte may be the oxidation number of the electrolyte itself at the time of manufacture or supply, or the average value of the oxidation number of the vanadium ion of the electrolyte supplied to the positive and negative electrodes, and may represent the average value of the oxidation number of the vanadium ion of the positive and negative electrolytes when the secondary battery is operated by charging and discharging.

[0054] In this specification, the reduction electrode part is an electrode where the oxidation number of vanadium ions decreases as a reduction reaction occurs, and may be referred to as a cathode part. In this specification, the oxidation electrode part is an electrode where the oxidation number of vanadium ions increases as an oxidation reaction occurs, and may be referred to as an anode part.

[0055] Figure 2 schematically illustrates a method for treating a vanadium ion-containing electrolyte according to an embodiment of the present invention.

[0056] The method for treating an electrolyte containing vanadium ions according to the present invention includes a process of removing metal impurities using an electrochemical method. This utilizes the principle that when the oxidation number of vanadium ions in the electrolyte solution in a charging cell is lower than the precipitation oxidation number of the metal impurity (e.g., 3), the metal impurity is precipitated (adsorbed) from the electrolyte solution to the electrode surface. Based on the standard reduction potential of vanadium, for example, V 3+ / V 2+If the standard reduction potential of vanadium is -0.25 V, the Mo element, which has a reduction potential of -0.20 V, can be adsorbed on an electrode such as carbon felt during reduction in the reduction electrode section. That is, when an electrolyte containing vanadium and metal impurities undergoes a reduction reaction in a charging cell, the oxidation number of the vanadium ion decreases from, for example, 3.5 to 2, and the metal impurity with a relatively low reduction potential is precipitated, i.e., adsorbed, on the electrode. By this principle, metal impurities can be removed from the vanadium-containing electrolyte, and the concentration of metal impurities in the vanadium-containing electrolyte can be lowered.

[0057] Referring to FIG. 2, the illustrated method for treating a vanadium ion-containing electrolyte includes a vanadium ion-containing electrolyte separation supply step (S210), a first charging reaction step (S220), a discharge reaction step (S230), a second charging reaction step (S240), and a vanadium ion-containing electrolyte mixing and recovery step (S250).

[0058] The vanadium ion-containing electrolyte separation and supply step (S210) separates the vanadium ion-containing electrolyte supplied from the vanadium ion-containing electrolyte storage unit into a first electrolyte and a second electrolyte. The vanadium ion-containing electrolyte may have an oxidation number of vanadium ions of 3.5. Here, the oxidation number of 3.5 may refer to an oxidation number of exactly 3.5, but may also refer to an oxidation number within a range of about 3.4 to 3.6 as the oxidation number of 3.5. The vanadium electrolyte contains vanadium ions and an acidic solution. The vanadium ions may be supplied by vanadium oxide, and may include, for example, one or more selected from the group consisting of V2O5, VOSO4, V2O3, NH4VO3, and V2O4, but is not necessarily limited thereto, and may be selected according to electrolyte production conditions, production target amount, etc. The acidic solution may include at least one selected from the group consisting of sulfuric acid, hydrochloric acid, nitric acid, and phosphoric acid, but for example, a sulfuric acid solution may be used. The concentration of the acidic solution may be, for example, 0.1 M to 10 M, for example, 1 M to 8 M, for example, 2 M to 5 M, but is not necessarily limited thereto, and may be appropriately adjusted depending on the type of acidic solution selected, etc. The concentration of vanadium ions in the electrolyte containing vanadium may be 1.5 M to 3.7 M.

[0059] The first electrolyte and the second electrolyte are simply separated into two branch paths, not by component. Therefore, both the vanadium ion of the first electrolyte and the vanadium ion of the second electrolyte can have an oxidation state of 3.5. The first electrolyte and the second electrolyte can have the same volume, but the volumes of the first electrolyte and the second electrolyte can be different depending on the need, such as for flow rate control. Meanwhile, the progression paths of the first electrolyte and the second electrolyte can be more clearly understood with reference to Fig. 3. In Figs. 2 and 3, ① represents the progression path of the first electrolyte, and ② represents the progression path of the second electrolyte.

[0060] In the first charging reaction step (S220), the vanadium ions of the first electrolyte are reduced while the vanadium ions of the second electrolyte are oxidized through the first charging reaction in the first cell. During this process, impurities contained in the first electrolyte can be removed from the first electrolyte by being adsorbed to the reduction electrode of the cell where the first charging reaction is performed.

[0061] In the first charging reaction step (S220), the oxidation number of the vanadium ion of the first electrolyte can be reduced from 3.5 to 2-3, and the oxidation number of the vanadium ion of the second electrolyte can be oxidized from 3.5 to 4-5.

[0062] In the discharge reaction step (S230), the vanadium ions of the first electrolyte are oxidized and the vanadium ions of the second electrolyte are reduced through a discharge reaction in the second cell. In the discharge reaction step (S230), the oxidation number of the vanadium ions of the first electrolyte may be oxidized from 2-3 to 3.5, and the oxidation number of the vanadium ions of the second electrolyte may be reduced from 4-5 to 3.5.

[0063] In the second charging reaction step (S240), the vanadium ions of the first electrolyte are oxidized while the vanadium ions of the second electrolyte are reduced through the second charging reaction in the third cell.

[0064] In the second charging reaction step (S240), a reverse voltage opposite to the voltage applied in the first charging reaction step (S240) is applied. Accordingly, in the first charging reaction step (S220), the vanadium ions of the first electrolyte are reduced and the vanadium ions of the second electrolyte are oxidized, but in the second charging reaction step (S240), the vanadium ions of the second electrolyte are reduced and the vanadium ions of the first electrolyte are oxidized. In the second charging reaction step (S240), the oxidation number of the vanadium ions of the first electrolyte can be oxidized from 3.5 to 4-5, and the oxidation number of the vanadium ions of the second electrolyte can be reduced from 3.5 to 2-3.

[0065] Through the second charging reaction step (S240), impurities contained in the second electrolyte can be removed from the second electrolyte by being precipitated / adsorbed on the reduction electrode of the cell where the second charging reaction is performed.

[0066] During the first charging reaction step (S220), the discharging step (S230), and the second charging reaction step (S240), the flow rates of the first electrolyte and the second electrolyte may be 1.5 L / h or less, more preferably 1.2 L / h or less, and even more preferably 1.0 L / h or less. If the flow rates of the first electrolyte and the second electrolyte are fast, the treatment time can be reduced, but the impurity removal efficiency may be reduced. That is, if the flow rate of the electrolyte is fast, the current increases due to the vanadium ions that can react, but the oxidation number of vanadium does not change significantly due to the short treatment time. The lower limit of the flow rates of the first electrolyte and the second electrolyte is not specifically set, but it is more preferably 0.5 L / h or more, considering that the treatment time becomes too long.

[0067] In addition, it is preferable that a voltage of 1.4 V or higher, more preferably 1.6 V or higher, is applied to the charging cell (first charging cell) where the first charging reaction step (S220) is performed, and a voltage of 1.4 V or higher, more preferably 1.6 V or higher, is applied to the charging cell (second charging cell) where the second charging reaction step (S240) is performed. When a voltage of 1.6 V or higher is applied to the first charging cell and the second charging cell, the impurity removal efficiency can be further improved. For example, when a high voltage of 1.6 V is applied, the probability that many impurities will be adsorbed on the carbon felt during the reduction process at the reduction electrode is higher than when a voltage of 1.4 to 1.5 V is applied based on the standard reduction potential. Therefore, when a voltage of 1.6 V is applied, the impurity removal efficiency can be increased. In fact, the impurity removal efficiency increased when a voltage of 1.6 V was applied compared to when voltages of 1.4 V and 1.5 V, which are less than 1.6 V, were applied to the first and second charging cells. When voltages of 1.4 V and 1.5 V were applied, high impurity removal efficiency was achieved only when the flow rates of the first and second electrolytes were as low as 0.5 L / h.

[0068] The efficiency is highest when the electrolyte flow rate is 1 L / h and the applied voltage is 1.6 V, which can be said to be the most ideal conditions.

[0069] Of course, high impurity removal efficiency can be achieved by lowering the flow rate even when a voltage of less than 1.6 V is applied.

[0070] In some embodiments, when the applied voltage for the first and second charging cells is A (V) and the flow rate of the vanadium electrolyte is B (L / h), it is preferable to satisfy the following relationship: 2.1 ≤ 2A - B. When the above equation is satisfied, a higher impurity removal efficiency can be exhibited compared to when the equation is not satisfied, and thus pressure generation can be suppressed in battery operation using the treated vanadium electrolyte.

[0071] The same voltage may be applied to the charging cell (first charging cell) in which the first charging reaction step (S220) is performed, the discharge cell (S230) in which the discharge reaction step (S230) is performed, and the charging cell (second charging cell) in which the second charging reaction step (S240) is performed. For example, a voltage of 1.5 V may be applied to all of the first charging cell, the discharge cell, and the second charging cell, or a voltage of 1.6 V may be applied to all of them.

[0072] Meanwhile, in the discharge step (S230), the discharge cell can be maintained in a short-circuited state. Even if the wires of the oxidation electrode (anode) and reduction electrode (cathode) of the discharge cell are short-circuited, no pressure is generated, and an electrolyte having a desired target oxidation number can be produced.

[0073] In the vanadium ion-containing electrolyte mixing and recovery step (S250), the first electrolyte and the second electrolyte are mixed to recover the vanadium ion-containing electrolyte having, for example, an oxidation number of 3.5 vanadium ions into the vanadium ion-containing electrolyte storage unit.

[0074] Meanwhile, as in the example illustrated in FIG. 2, after the first charging reaction step (S220), the discharging reaction step (S230), or the second charging reaction step (S240) is performed, a process of monitoring the state of charge of the first electrolyte and the second electrolyte or the oxidation number of the first electrolyte and the second electrolyte may be additionally included. This can be performed through OCV (Open Cell Voltage) measurement, etc. For example, even if the current density value is high, there may be a possibility that the potential difference between the positive and negative electrodes may be minimal, and by checking the potential difference between the electrolyte passing to the oxidation electrode section and the electrolyte passing to the reduction electrode section through OCV measurement, it is possible to determine whether the process is actually performed properly.

[0075] After the step of performing the method for treating a vanadium ion-containing electrolyte according to the present invention, a refresh step may be additionally performed. The refresh step is intended to remove impurities adsorbed on the reduction electrode.

[0076] The refresh step can be performed by applying a reverse voltage to the cell or all cells that need refreshing to desorb metal impurity ions adsorbed on an electrode such as carbon felt. Since each metal impurity ion has a potential for adsorption, the principle is to utilize this in reverse. That is, for at least one of the first charging cell, the discharge cell, and the second charging cell, an electrolyte containing vanadium ions having an oxidation number of, for example, 3.5 is supplied, and then a reverse voltage is applied (i.e., +- conversion) to desorb impurities adsorbed on the reduction electrode into the electrolyte containing vanadium ions, which can be performed as an electrochemical process.

[0077] The application of the reverse voltage can be performed by applying a reverse voltage of 1.4 to 2.1 V for more than 1 minute. This takes into account the voltage and time required for the desorption of electrochemical impurities.

[0078] Figure 3 schematically illustrates a device for processing a vanadium ion-containing electrolyte according to an embodiment of the present invention.

[0079] Referring to FIG. 3, a vanadium ion-containing electrolyte treatment device according to an embodiment of the present invention includes a vanadium ion-containing electrolyte supply line (310), a first cell (320), a second cell (330), a third cell (340), and a vanadium ion-containing electrolyte recovery line (350).

[0080] In Fig. 3, the part marked with (+) of the first cell (320), the second cell (330), and the third cell (340) means an oxidation electrode part (anode part), and the part marked with (-) means a reduction electrode part (cathode part). The oxidation electrode part includes an electrode, i.e., an oxidation electrode (anode), and the reduction electrode part includes an electrode, i.e., a reduction electrode (cathode).

[0081] The vanadium ion-containing electrolyte supply line (310) supplies the vanadium ion-containing electrolyte by separating it into a first electrolyte and a second electrolyte from the electrolyte storage unit (301) that stores the vanadium ion-containing electrolyte. The vanadium ion-containing electrolyte storage unit (301) can store the vanadium ion-containing electrolyte having an oxidation number of 3.5.

[0082] In the first cell (320), a first charging reaction is performed on the first electrolyte and the second electrolyte. The first cell (320) includes a first reduction electrode unit (320a) in which a reduction reaction is performed by receiving the first electrolyte, and a first oxidation electrode unit (320b) in which an oxidation reaction is performed by receiving the second electrolyte, with a separator therebetween. In the first cell (320), the reduction electrode unit (320a) is arranged to be in contact with the first electrolyte, so that vanadium ions in the first electrolyte are reduced and their oxidation number is lowered. Specifically, in the first cell (320), through the first charging reaction, the oxidation number of the vanadium ions in the first electrolyte is lowered in the first reduction electrode unit, and the oxidation number of the vanadium ions in the second electrolyte is increased in the first oxidation electrode unit. In this process, impurities contained in the first electrolyte can be removed from the first electrolyte by being adsorbed on the reduction electrode of the reduction electrode unit of the first cell.

[0083] In the second cell (330), a discharge reaction is performed on the first electrolyte and the second electrolyte that have passed through the first cell. The second cell includes a second oxidation electrode unit (330a) in which an oxidation reaction is performed by receiving a first electrolyte from the first reduction electrode unit of the first cell (320), and a second reduction electrode unit (330b) in which a reduction reaction is performed by receiving a second electrolyte from the first oxidation electrode unit of the first cell (320). In the second cell (330), the reduction electrode unit (330b) is arranged to be in contact with the second electrolyte, so that vanadium ions in the second electrolyte are reduced and the oxidation number is lowered. In addition, in the second cell (330), the oxidation electrode unit (330a) is arranged to be in contact with the first electrolyte, so that vanadium ions in the first electrolyte are oxidized and the oxidation number is increased.

[0084] In the third cell (340), a second charging reaction is performed on the first electrolyte and the second electrolyte that have passed through the second cell (330). The third cell (340) includes a third oxidation electrode unit (340a) in which an oxidation reaction is performed by receiving the first electrolyte from the second oxidation electrode unit (330a) of the second cell (330), and a third reduction electrode unit (340b) in which a reduction reaction is performed by receiving the second electrolyte from the second reduction electrode unit (330b) of the second cell (330). In the third cell (340), the reduction electrode unit (340b) is arranged to be in contact with the second electrolyte, so that vanadium ions of the second electrolyte are reduced and the oxidation number is lowered. That is, in the third cell (340), the oxidation number of the vanadium ion of the first electrolyte increases in the third oxidation electrode section (340a) through the second charging reaction, and the oxidation number of the vanadium ion of the second electrolyte decreases in the third reduction electrode section (340b). In this process, impurities contained in the second electrolyte can be removed from the second electrolyte by being adsorbed on the reduction electrode of the reduction electrode section (340b) of the third cell (340).

[0085] The vanadium ion-containing electrolyte recovery line (350) merges the first electrolyte and the second electrolyte that have passed through the third cell and supplies them to the electrolyte storage unit (301').

[0086] According to the device according to FIG. 3, for example, in the first cell (320), the oxidation number of the vanadium ion of the first electrolyte of the first reduction electrode unit is reduced from 3.5 to 2-3, the oxidation number of the vanadium ion of the second electrolyte of the first oxidation electrode unit is oxidized from 3.5 to 4-5, in the second cell, the oxidation number of the vanadium ion of the first electrolyte of the second oxidation electrode unit is oxidized from 2-3 to 3.5, and the oxidation number of the vanadium ion of the second electrolyte of the second reduction electrode unit is reduced from 4-5 to 3.5, and in the third cell (340), the oxidation number of the vanadium ion of the first electrolyte of the third oxidation electrode unit is oxidized from 3.5 to 4-5, and the oxidation number of the vanadium ion of the second electrolyte of the third reduction electrode unit can be reduced from 3.5 to 2-3.

[0087] A voltage of 1.5 V or higher may be applied to each of the first cell (320) and the third cell (340). In this case, the same voltage may be applied to the first cell (320), the second cell (330), and the third cell (340).

[0088] As another example, the second cell (330) can be maintained in a short-circuited state. Even if the wires of the oxidation electrode (anode) and reduction electrode (cathode) of the discharge cell are short-circuited, no pressure is generated, and an electrolyte having a desired target oxidation number can be produced.

[0089] The device for treating a vanadium ion-containing electrolyte according to the present invention may further include a control unit that monitors and / or controls at least one of the flow rates of the first electrolyte and the second electrolyte, the state of charge of the first electrolyte and the second electrolyte, and the voltage applied to the first to third cells. For example, the OCV of FIG. 3 monitors the state of charge of the first and third cells, and can determine whether impurities in the electrolyte are actually capable of being adsorbed through the value of the potential difference between the positive and negative electrodes.

[0090] Example

[0091] Hereinafter, the present invention will be described in more detail by describing experimental examples of the present invention. However, these are only examples of the present invention and the present invention is not limited thereto.

[0092] Using the device illustrated in Fig. 3, 2 L of a 3.5-valent vanadium ion-containing electrolyte was treated. In treating the vanadium ion-containing electrolyte, as shown in Table 1, the flow rates of the first and second electrolytes, the treatment time, the voltage applied to each cell, and the current were varied, and the generation of pressure was measured.

[0093] Whether pressure was generated and the degree of pressure increase was measured using the pressure measurement cell shown in Fig. 4.

[0094] The structure of the pressure measurement cell used in the experiment is shown in Fig. 4.

[0095] A reduction electrode part (reduction electrode and electrolyte) (510a) was placed on the upper part of the separator (520), and an oxidation electrode part (oxidation electrode and electrolyte) (510b) was placed on the lower part of the separator. A cell including a carbon collector (530a, 530b) and a metal collector (540a, 540b) was formed on the surface of the reduction electrode part and the oxidation electrode part, and the pressure of the cell was measured through a pressure gauge (550). Carbon felt, 99*99 mm in size, was used as the reduction electrode and the oxidation electrode. A 1.7 M vanadium electrolyte was used as the vanadium electrolyte, with an injection amount of 138 g. An ion-selective separator was used as the separator. An aluminum collector was used as the metal collector. A carbon separator plate was used as the carbon collector. A product of Sensys was used as the pressure gauge (550).

[0096] Pressure measurements were performed to determine whether pressure occurred during discharge during the charge / discharge cycle of the pressure measurement cell. Measurements began after 10 cycles to ensure cell stabilization. A total of 100 cycles were performed, and the pressure increase was determined based on the pressure value at cycle 11.

[0097] [Table 1]

[0098]

[0099] In the examples and comparative examples of Table 1, the voltage values ​​are given the same but the current values ​​are different. This may be due to differences in the state of the cell. In this case, it can be seen that the current values ​​are measured differently because the flow rate is different.

[0100] Referring to Table 1, the following conclusions were obtained. When the applied voltage was 1.6 V, no pressure was generated at a flow rate of less than 2 L / h, indicating high impurity removal efficiency. When the applied voltage was 1.5 V, high impurity removal efficiency was observed only when the flow rate was 0.8 L / h or less, and when the applied voltage was 1.4 V, high impurity removal efficiency was observed only when the flow rate was 0.5 L / h or less. From this, it can be seen that high impurity removal efficiency is exhibited when the applied voltage (A) and the flow rate (B) of the vanadium electrolyte for the first and second charging cells satisfy the following relationship: 2.1 ≤ 2A - B. In the case of Example 1-4, the above equation was satisfied, whereas in the case of Comparative Example 1-4, the above equation was not satisfied.

[0101] The evaluation results for each example and comparative example are as follows:

[0102] Example 1: Flow rate 1 L / h, applied voltage 1.6 V, high voltage expanded the range of removable impurities (e.g., metal ions, etc.), and no pressure was generated.

[0103] Example 2: Flow rate 0.8 L / h, applied voltage 1.5 V, applied voltage 0.1 V lower than Example 1, but as the flow rate decreased by 0.2 L / h, the time for impurities to be adsorbed on the negative solid electrode (carbon felt) increased, so no pressure was generated.

[0104] Example 3: Flow rate 0.5 L / h, applied voltage 1.4 V, applied voltage 0.2 V lower than Example 1, but as the flow rate decreased by 0.5 L / h, the time for impurities to be adsorbed on the cathode solid electrode increased, so no pressure was generated.

[0105] Example 4: Flow rate 1 L / h, applied voltage of 1.6 V to cells 1 and 3, no current was applied to cell 2, and the cathode and anode were connected to each other to create a short circuit, but no pressure was generated. This shows that it is important for the conditions of cells 1 and 3 to occur efficiently.

[0106] Comparative Example 1: Flow rate 2 L / h, applied voltage 1.6 V, as the flow rate increased by 1 L / h compared to Example 1, the time for impurities to be adsorbed on the cathode solid electrode decreased, resulting in pressure generation.

[0107] Comparative Example 2: Flow rate 1 L / h, applied voltage 1.5 V, the flow rate increased by 0.2 L / h compared to Example 2, but as the applied voltage decreased, the time for impurities to be adsorbed on the cathode solid electrode decreased, resulting in pressure generation.

[0108] Comparative Example 3: With a flow rate of 1 L / h and an applied voltage of 1.4 V, the flow rate increased by 0.5 L / h compared to Example 3, so that the time for impurities to be adsorbed on the cathode solid electrode decreased, resulting in pressure generation.

[0109] Comparative Example 4: Flow rate 0.8 L / h, applied voltage 1.4 V, as the flow rate increased by 0.3 L / h compared to Example 3, the time for impurities to be adsorbed on the cathode solid electrode decreased, resulting in pressure generation.

[0110] After separately supplying an electrolyte containing vanadium (V) with an oxidation number of 3.5 to a charging cell and applying a voltage of 1.6 V to remove metal impurities from the reduction electrode section, the process was repeated three times (Comparative Example 5) and four times (Comparative Example 6), and after performing the treatment according to Example 1, the pressure measurement results are shown in Table 2 and Fig. 5.

[0111] [Table 2]

[0112]

[0113] Referring to Table 2 and Figure 5, when comparing Comparative Examples 5 and 6, pressure was generated in Comparative Example 5 because the number of processes was three. This means that at least four processes are required to remove impurities using the method illustrated in Figure 1. However, in the case of Example 1, it can be seen that no pressure was generated with only one process.

[0114] Table 3 and Figure 6 show the results of measuring whether pressure was generated when refreshing was performed once (Example 5) and when refreshing was performed twice (Example 6) after processing according to Example 1.

[0115] The refresh process for each cell was performed by switching the wires connected to the reduction electrode and oxidation electrode of each cell, and then applying a voltage of 1.6 V for 2 minutes while supplying an electrolyte containing vanadium ions with an oxidation number of 3.5.

[0116] [Table 3]

[0117]

[0118] Referring to Table 3 and Figure 6, it can be seen that the processing capacity can be increased without generating pressure through the refresh process.

[0119] For example, if it is possible to remove impurities from 500 L of vanadium electrolyte without a refresh process as in Example 1, it can be seen that when the refresh process is performed once, impurities from 1000 L of vanadium electrolyte can be removed, and when the refresh process is performed twice, impurities from 1500 L of vanadium electrolyte can be removed. Therefore, it can be seen that the vanadium electrolyte treatment capacity can be increased through the refresh process.

[0120] Although the embodiments of the present specification have been described in more detail with reference to the attached drawings, the present specification is not necessarily limited to these embodiments, and various modifications may be implemented without departing from the technical spirit of the present specification. Therefore, the embodiments disclosed in this specification are not intended to limit the technical spirit of the present specification, but to explain, and the scope of the technical spirit of the present specification is not limited by these embodiments. Therefore, it should be understood that the embodiments described above are illustrative in all respects and not restrictive. The scope of protection of this specification should be interpreted by the claims, and all technical ideas within a scope equivalent thereto should be interpreted as being included in the scope of rights of this specification.

Claims

1. (a) A step of separating a vanadium ion-containing electrolyte into a first electrolyte and a second electrolyte; (b) a step of oxidizing vanadium ions of the second electrolyte while reducing vanadium ions of the first electrolyte through a first charging reaction; (c) a step of reducing vanadium ions of the second electrolyte while oxidizing vanadium ions of the first electrolyte through a discharge reaction; (d) a step of reducing vanadium ions of the second electrolyte while oxidizing vanadium ions of the first electrolyte through a second charging reaction; and (e) A method for treating an electrolyte containing vanadium ions, comprising the step of mixing the first electrolyte and the second electrolyte.

2. In paragraph 1, In the step (b) above, impurities contained in the first electrolyte are removed, A method for treating an electrolyte containing vanadium ions, wherein impurities contained in the second electrolyte are removed in the step (d).

3. In paragraph 1, A method for treating a vanadium ion-containing electrolyte, wherein the above vanadium ion-containing electrolyte has an oxidation number of 3.

5.

4. In paragraph 3, In the step (b) above, the oxidation number of the vanadium ion of the first electrolyte is reduced from 3.5 to 2-3, and the oxidation number of the vanadium ion of the second electrolyte is oxidized from 3.5 to 4-5. In the step (c) above, the oxidation number of the vanadium ion of the first electrolyte is oxidized from 2-3 to 3.5, and the oxidation number of the vanadium ion of the second electrolyte is reduced from 4-5 to 3.

5. A method for treating an electrolyte containing vanadium ions, wherein in the step (d) above, the oxidation number of the vanadium ions of the first electrolyte is oxidized from 3.5 to 4 to 5, and the oxidation number of the vanadium ions of the second electrolyte is reduced from 3.5 to 2 to 3.

5. In paragraph 1, A method for treating an electrolyte containing vanadium ions, wherein the flow rates of the first electrolyte and the second electrolyte in steps (b) to (d) are 1.5 L / h or less.

6. In paragraph 1, In the step (b) above, a voltage of 1.4 V or higher is applied to the cell where the first charging reaction is performed, A method for treating an electrolyte containing vanadium ions, wherein, in the step (d) above, a voltage of 1.4 V or higher is applied to a cell in which the second charging reaction is performed.

7. In paragraph 6, A method for treating a vanadium ion-containing electrolyte, wherein the same voltage is applied to a cell in which the first charging reaction is performed, a cell in which the discharge reaction is performed, and a cell in which the second charging reaction is performed.

8. In paragraph 6, A method for treating an electrolyte containing vanadium ions, wherein in the step (c) above, the cell in which the discharge reaction is performed is maintained in a short-circuit state.

9. In paragraph 1, A method for treating a vanadium ion-containing electrolyte, wherein the voltage and flow rate are controlled so as to satisfy the following relationship: 2.1 ≤ 2A - B, when the voltage applied to the cell in which the first charging reaction is performed and the cell in which the second charging reaction is performed is A (V), and the flow rates of the first electrolyte and the second electrolyte in steps (b) to (d) are B (L / h).

10. In paragraph 1, A method for treating a vanadium ion-containing electrolyte, further comprising, after step (e) above, a step of supplying a vanadium ion-containing electrolyte to at least one of a cell in which the first charging reaction is performed, a cell in which the discharge reaction is performed, and a cell in which the second charging reaction is performed, and then applying a reverse voltage to desorb impurities adsorbed on an electrode into the vanadium ion-containing electrolyte.

11. In paragraph 10, A method for treating an electrolyte containing vanadium ions, wherein the application of the reverse voltage is performed by applying a reverse voltage of 1.4 to 2.1 V for 1 minute or longer.

12. A supply line for supplying a vanadium ion-containing electrolyte from an electrolyte storage unit by separating it into a first electrolyte and a second electrolyte; A first cell in which a first charging reaction is performed for the first electrolyte and the second electrolyte; A second cell in which a discharge reaction is performed on the first electrolyte and the second electrolyte that have passed through the first cell; A third cell in which a second charging reaction is performed on the first electrolyte and the second electrolyte that have passed through the second cell; and It includes a recovery line that merges the first electrolyte and the second electrolyte that have passed through the third cell and supplies them to the electrolyte storage unit. A device for treating an electrolyte containing vanadium ions, wherein in the first cell, the reduction electrode part is arranged to be in contact with the first electrolyte, and in the third cell, the reduction electrode part is arranged to be in contact with the second electrolyte.

13. In paragraph 12, The first cell includes a first reduction electrode part supplied with the first electrolyte and a first oxidation electrode part supplied with the second electrolyte, The second cell includes a second oxidation electrode section that receives the first electrolyte from the first reduction electrode section of the first cell, and a second reduction electrode section that receives the second electrolyte from the first oxidation electrode section of the first cell. A device for treating a vanadium ion-containing electrolyte, wherein the third cell includes a third oxidation electrode section that receives the first electrolyte from the second oxidation electrode section of the second cell, and a third reduction electrode section that receives the second electrolyte from the second reduction electrode section of the second cell.

14. In paragraph 13, In the first cell, the oxidation number of the vanadium ion of the first electrolyte decreases in the first reduction electrode section through the first charging reaction, and the oxidation number of the vanadium ion of the second electrolyte increases in the first oxidation electrode section. In the second cell, the oxidation number of the vanadium ion of the first electrolyte increases in the second oxidation electrode section through a discharge reaction, and the oxidation number of the vanadium ion of the second electrolyte decreases in the second reduction electrode section. A device for treating an electrolyte containing vanadium ions, wherein in the third cell, the oxidation number of vanadium ions of the first electrolyte increases in the third oxidation electrode section through a second charging reaction, and the oxidation number of vanadium ions of the second electrolyte decreases in the third reduction electrode section.

15. In paragraph 13, The above electrolyte storage unit is a device for processing a vanadium ion-containing electrolyte, which stores an electrolyte containing vanadium ions having an oxidation number of 3.

5.

16. In paragraph 15, In the first cell, the oxidation number of the vanadium ion of the first electrolyte of the first reduction electrode part is reduced from 3.5 to 2-3, and the oxidation number of the vanadium ion of the second electrolyte of the first oxidation electrode part is oxidized from 3.5 to 4-5. In the second cell, the oxidation number of the vanadium ion of the first electrolyte of the second oxidation electrode part is oxidized from 2-3 to 3.5, and the oxidation number of the vanadium ion of the second electrolyte of the second reduction electrode part is reduced from 4-5 to 3.

5. A device for treating an electrolyte containing vanadium ions, wherein the oxidation number of vanadium ions of the first electrolyte of the third oxidation electrode section in the third cell is oxidized from 3.5 to 4 to 5, and the oxidation number of vanadium ions of the second electrolyte of the third reduction electrode section is reduced from 3.5 to 2 to 3.

17. In paragraph 12, A device for processing a vanadium ion-containing electrolyte, wherein a voltage of 1.4 V or higher is applied to each of the first cell and the third cell.

18. In paragraph 17, A device for treating a vanadium ion-containing electrolyte, wherein the same voltage is applied to the first cell, the second cell, and the third cell.

19. In Article 16, A device for processing a vanadium ion-containing electrolyte, wherein the second cell is maintained in a short-circuit state.

20. In paragraph 12, A method for treating an electrolyte containing vanadium ions, wherein the voltage and flow rate are controlled so as to satisfy the following relationship: 2.1 ≤ 2A - B, when the applied voltage to the first cell and the third cell is A (V) and the flow rates of the first electrolyte and the second electrolyte are B (L / h).

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