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, wherein the impurities contained in a solution to be processed can be removed even at a relatively low voltage through a multi-stage oxidation-reduction reaction using a counter solution, so that the impurities contained in the electrolyte solution containing vanadium ions can be efficiently removed even without repeating a charging reaction of the electrolyte solution containing vanadium ions several times.

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 vanadium redox flow batteries (VRFBs) utilize electrolytes containing vanadium ions. Electrolytes containing vanadium ions are aqueous, so they offer high safety against explosions and other issues 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 have the longest lifespan among oxidation-reduction secondary batteries, are advantageous for increasing capacity, and can be separated and reused through the electrochemical reaction of charge and discharge in secondary batteries, resulting in cost savings.

[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 an electrolyte containing vanadium ions, 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 an electrolyte containing vanadium ions comprises the steps of: (a) supplying a solution to be treated, which is an electrolyte containing vanadium ions to be treated, to a reduction electrode section of a first oxidation-reduction cell, and supplying a counter solution containing vanadium ions to an oxidation electrode section of the first oxidation-reduction cell; (b) reducing vanadium ions of the solution to be treated while oxidizing vanadium ions of the counter solution in the first oxidation-reduction cell; (c) oxidizing vanadium ions of the solution to be treated supplied from the first oxidation-reduction cell in a second oxidation-reduction cell; and (d) reducing vanadium ions of the solution to be treated supplied from the second oxidation-reduction cell while reducing vanadium ions of the counter solution supplied from the first oxidation-reduction cell in a third oxidation-reduction cell, wherein in step (c), the vanadium ions of the solution to be treated supplied from the third oxidation-reduction cell are reduced.

[0016] In the above step (b), impurities contained in the solution to be processed can be removed.

[0017] The vanadium ion of the solution to be treated in the above step (a) may have an oxidation number of 3.5.

[0018] In the step (b), the vanadium ions of the solution to be treated are reduced to an oxidation number of 2 to 3, and the vanadium ions of the counter solution are oxidized to an oxidation number of 4 to 5, in the step (c), the vanadium ions of the solution to be treated supplied from the first oxidation-reduction cell are oxidized to an oxidation number of 3.5, and the vanadium ions of the solution to be treated supplied from the third oxidation-reduction cell are reduced to an oxidation number of 3.5, and in the step (d), the vanadium ions of the solution to be treated supplied from the second oxidation-reduction cell are oxidized to an oxidation number of 4 to 5, and the vanadium ions of the counter solution supplied from the first oxidation-reduction cell can be reduced to an oxidation number of 3.5.

[0019] In the step (b), a voltage of 1.5 V or less may be applied to the first oxidation-reduction cell, and in the step (d), a voltage of 1.3 V or more may be applied to the third oxidation-reduction cell.

[0020] The difference between the current density of the first oxidation-reduction cell and the current density of the third oxidation-reduction cell is 0.5 A / m 2 It could be as follows:

[0021] The applied voltage or current density of the third oxidation-reduction cell can be adjusted according to the required oxidation number of the solution to be treated.

[0022] The above second oxidation-reduction cell can be maintained in a short state.

[0023] After recovering the treated solution through steps (b) to (d) above, a step of supplying a vanadium ion-containing electrolyte for refreshing to the first oxidation-reduction cell and applying a reverse voltage opposite to the polarity of the voltage applied in step (b) to desorb impurities adsorbed on the reduction electrode with the vanadium ion-containing electrolyte for refreshing may be additionally included.

[0024] According to the present invention for solving the above problem, a device for treating an electrolyte containing vanadium ions comprises: a treatment target solution storage unit for storing a treatment target solution, which is a vanadium ion-containing electrolyte to be treated; a counter solution storage unit for storing a counter solution containing vanadium ions; a first oxidation-reduction cell including a first reduction electrode unit connected to the treatment target solution storage unit and supplied with the treatment target solution, and a first oxidation electrode unit connected to the counter solution storage unit and supplied with the counter solution; a second oxidation-reduction cell including a second oxidation electrode unit to which the treatment target solution is supplied from the first oxidation-reduction cell, and a second reduction electrode unit to which the treatment target solution is supplied from a third oxidation-reduction cell; and a third oxidation-reduction cell including a third oxidation electrode unit to which the treatment target solution is supplied from the second oxidation-reduction cell, and a third reduction electrode unit to which the counter solution is supplied from the first oxidation-reduction cell.

[0025] The treated solution can be discharged from the second reduction electrode section of the second oxidation-reduction cell.

[0026] The above-mentioned target solution storage unit and the corresponding solution storage unit can each store an electrolyte containing vanadium ions having an oxidation number of 3.5.

[0027] In the first oxidation-reduction cell, vanadium ions of the solution to be treated in the reduction electrode section are reduced to an oxidation number of 2 to 3, vanadium ions of the counter solution in the oxidation electrode section are oxidized to an oxidation number of 4 to 5, and in the second oxidation-reduction cell, vanadium ions of the solution to be treated in the reduction electrode section and the oxidation electrode section can be reduced and oxidized to an oxidation number of 3.5, respectively.

[0028] In the third oxidation-reduction cell, vanadium ions in the target solution of the oxidation electrode section can be oxidized to an oxidation number of 4 to 5, and vanadium ions in the counter solution of the reduction electrode section can be reduced to an oxidation number of 3.5.

[0029] A voltage of 1.5 V or lower may be applied to the first oxidation-reduction cell, and a voltage of 1.3 V or higher may be applied to the third oxidation-reduction cell.

[0030] The difference between the current density of the first oxidation-reduction cell and the current density of the third oxidation-reduction cell is 0.5 A / m 2 It could be as follows:

[0031] The applied voltage or current density of the third oxidation-reduction cell can be adjusted according to the required oxidation number value of the solution to be treated.

[0032] According to the method and device for treating a vanadium ion-containing electrolyte according to the present invention, impurities contained in the solution to be treated can be removed even at relatively low voltages through a multi-stage oxidation-reduction reaction using a counter solution. This allows for efficient removal of impurities contained in the vanadium ion-containing electrolyte without having to repeat the charging reaction of the vanadium ion-containing electrolyte multiple times.

[0033] In addition, there is an advantage in that only impurities can be removed without changing the oxidation number through current control of the oxidation-reduction cells.

[0034] In addition, a decrease in impurity removal efficiency can be prevented by performing a refresh process using reverse voltage on the oxidation-reduction cell where impurities are removed.

[0035] 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.

[0036] Figure 1 schematically illustrates a general electrochemical removal method for metal impurities.

[0037] Figure 2 schematically illustrates a method for treating a vanadium ion-containing electrolyte according to an embodiment of the present invention.

[0038] Figure 3 schematically illustrates a device for processing a vanadium ion-containing electrolyte according to an embodiment of the present invention.

[0039] Figure 4 shows an example of a device capable of measuring the pressure of a cell.

[0040] Figure 5 shows the pressure measurement results of the examples and comparative examples.

[0041] 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.

[0042] Throughout this specification, unless otherwise specifically stated, each component may be singular or plural.

[0043] In interpreting the components in this specification, even if there is no separate explicit description, it is interpreted to include the range of error.

[0044] 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.

[0045] 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.

[0046] Unless otherwise specified in this specification, any reference to a unit is interpreted to mean “weight.”

[0047] 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.

[0048] 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.

[0049] 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.

[0050] Figure 2 schematically illustrates a method for treating a vanadium ion-containing electrolyte according to an embodiment of the present invention.

[0051] 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.

[0052] Referring to FIG. 2, the illustrated method for treating a vanadium ion-containing electrolyte includes a step of supplying a solution to be treated and a counter solution (S210), a first oxidation-reduction reaction step (S220), a second oxidation-reduction reaction step (S230), and a third oxidation-reduction reaction step (S240).

[0053] In the step of supplying the solution to be treated and the counter solution (S210), the electrolyte containing vanadium ions to be treated (hereinafter, the solution to be treated) is supplied to the reduction electrode section of the first oxidation-reduction cell, and the counter solution is supplied to the oxidation electrode section. Meanwhile, the progression paths of the solution to be treated and the counter solution can be more clearly understood with reference to Fig. 3. In Fig. 3, ① represents the progression path of the solution to be treated, and ② represents the progression path of the counter solution.

[0054] The vanadium ions of the solution to be treated and the counter solution may have an oxidation number of 3.5. Here, the oxidation number of 3.5 may mean exactly 3.5, but may also mean an oxidation number within the range of about 3.4 to 3.6. 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 one or more 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, for example, 1.5 M to 3.7 M.

[0055] In the first oxidation-reduction reaction step (S220), a counter solution containing vanadium ions is supplied to the oxidation electrode section of the first oxidation-reduction cell. In the first oxidation-reduction cell, vanadium ions of the solution to be treated are reduced while vanadium ions of the counter solution are oxidized. By this reduction of vanadium ions, the oxidation number of the vanadium ions is lowered to 2 to 3, and accordingly, impurities contained in the solution to be treated are removed from the solution to be treated by being precipitated / adsorbed to the reduction electrode. Meanwhile, vanadium ions of the counter solution are oxidized to an oxidation number of 4 to 5.

[0056] In the second oxidation-reduction reaction step (S230), the vanadium ions of the solution to be treated supplied from the first oxidation-reduction cell are oxidized in the second oxidation-reduction cell. At this time, the vanadium ions of the solution to be treated supplied from the third oxidation-reduction cell, which will be described later, are reduced in the reduction electrode section of the second oxidation-reduction cell. In this process, the vanadium ions of the solution to be treated supplied from the first oxidation-reduction cell can be oxidized to an oxidation number of 3.5, and the vanadium ions of the solution to be treated supplied from the third oxidation-reduction cell can be reduced to an oxidation number of 3.5.

[0057] In the third oxidation-reduction reaction step (S240), in the third oxidation-reduction cell, vanadium ions of the solution to be treated supplied from the second oxidation-reduction cell are oxidized while vanadium ions of the counter solution supplied from the first oxidation-reduction cell are reduced. In this process, vanadium ions of the solution to be treated supplied from the second oxidation-reduction cell can be oxidized to an oxidation number of 4 to 5, and vanadium ions of the counter solution supplied from the first oxidation-reduction cell can be reduced to an oxidation number of 3.5.

[0058] Finally, a treated solution in which a reduction reaction of the second oxidation-reduction reaction step (S230) has been performed, for example, a treated solution having an oxidation number of 3.5 vanadium ions, can be recovered.

[0059] Meanwhile, each cell where redox reactions are performed may additionally include a process for monitoring the oxidation states of the target solution and the corresponding solution. This can be accomplished through Open Cell Voltage (OCV) measurements, for example. For example, even if the current density value is high, there is a possibility that the potential difference between the anode and cathode may be minimal. By measuring the OCV, the potential difference between the electrolyte passing through the oxidation electrode and the reduction electrode can be confirmed, allowing for a determination of whether the process is actually proceeding properly.

[0060]

[0061] During each oxidation-reduction reaction, the flow rate of the solution to be treated 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 rate of the solution to be treated is too fast, the treatment time can be reduced, but the impurity removal efficiency may decrease. That is, if the flow rate of the solution to be treated 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. For this reason, the difference in the electrolyte potential of the anode and cathode is not large, so the metal ion (impurity) removal effect is reduced.

[0062] There is no specific lower limit for the flow rate of the solution to be treated, but considering that the treatment time becomes too long, it is more preferable to have a flow rate of 0.5 L / h or more.

[0063] A voltage of 1.5 V or lower, for example, 1.3 to 1.5 V, may be applied to the first oxidation-reduction cell. In the case of Fig. 1, a voltage of 1.6 V or higher needs to be applied, but in the case of the present invention, sufficient impurity removal efficiency can be exhibited even when a voltage of 1.4 V or 1.5 V is applied. By rapidly circulating a counter solution to the oxidation electrode, which is the opposite electrode to the reduction electrode of the first oxidation-reduction cell, operation can be performed at a relatively low voltage.

[0064] Sufficient impurity adsorption time can be secured by applying a voltage of approximately 1.5 V together with a flow rate of 1.5 L / h or less. Of course, even if a voltage of 1.5 V or less is applied to the first oxidation-reduction cell, the impurity adsorption efficiency can be achieved, but in this case, a slower flow rate is required. The voltage applied to the first oxidation-reduction cell is related to the flow rate of the counter solution in the anode electrode section. When a voltage of 1.5 V or less is applied to the cathode of the cathode electrode section, assuming that the flow rate of the counter solution in the anode electrode section is the same, the slower the flow rate of the solution to be treated in the cathode electrode section, the higher the impurity removal effect. This is because the slower the flow rate, the greater the amount of impurities that can be adsorbed on an electrode such as carbon felt. However, if the cell voltage is low, metal impurity ions with different reduction potentials are not removed, so the applied voltage can be controlled according to the metal impurity ions to be removed.

[0065] Meanwhile, a voltage of 1.3 V or higher, for example, 1.3 V to 1.5 V, can be applied to the third oxidation-reduction cell. In the case of the third oxidation-reduction cell, current density control is important. The difference between the current density of the first oxidation-reduction cell and the current density of the third oxidation-reduction cell should be 0.5 A / m 2 It is preferable that the current density of the first oxidation-reduction cell be the same as that of the third oxidation-reduction cell, and more preferably, the current density of the first oxidation-reduction cell and the current density of the third oxidation-reduction cell may be the same. In this case, the change in the oxidation number of the vanadium ion can be minimized.

[0066] Of course, depending on the purpose, a treatment solution other than 3.5 oxidation number may be required. For example, when operating a battery using a treatment solution, a vanadium ion oxidation number slightly greater or less than 3.5 may be required to resolve concentration imbalances between the reduction electrode and oxidation electrode, or volume imbalances between the reduction electrode and oxidation electrode. In this case, the applied voltage or current density of the third oxidation-reduction cell is adjusted so that the applied voltage or current density of the third oxidation-reduction cell is different from the applied voltage or current density of the first oxidation-reduction cell.

[0067] In this way, according to the method for treating a vanadium ion-containing electrolyte according to the present invention, the applied voltage or current density of the third oxidation-reduction cell can be adjusted according to the required oxidation number of the solution to be treated. That is, by adjusting the applied voltage or current density of the third oxidation-reduction cell, the vanadium ion-containing electrolyte can be treated to have a desired oxidation number while removing impurities.

[0068]

[0069] The second redox cell can be subjected to various voltages and, in some cases, can be maintained in a short-circuited state. The current density of the second redox cell can affect the processing efficiency of the third redox cell.

[0070]

[0071] 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. This refresh step can be performed by applying a reverse voltage to the cell requiring refreshing to desorb metal impurity ions adsorbed on an electrode such as carbon felt. This principle utilizes the reverse potential of each metal impurity ion to facilitate adsorption.

[0072] Specifically, after recovering the treated solution through the above processes (S210 to S240), a vanadium ion-containing electrolyte for refreshing (e.g., a vanadium ion-containing electrolyte having an oxidation number of 3.5) may be supplied to the first oxidation-reduction cell in which the impurity removal reaction is performed, and a reverse voltage opposite to the polarity of the voltage applied in the first oxidation-reduction reaction may be applied (i.e., the voltage may be applied by switching + to -). Through this, the impurities adsorbed on the reduction electrode may be desorbed into the vanadium ion-containing electrolyte.

[0073] 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.

[0074]

[0075] Figure 3 schematically illustrates a device for processing a vanadium ion-containing electrolyte according to an embodiment of the present invention.

[0076] Referring to FIG. 3, a vanadium ion-containing electrolyte treatment device according to an embodiment of the present invention includes a treatment target solution storage unit (301), a counterpart solution storage unit (302), a first oxidation-reduction cell (310), a second oxidation-reduction cell (320), and a third oxidation-reduction cell (330).

[0077] In Fig. 3, the part marked with (+) of the first oxidation-reduction cell (310), the second oxidation-reduction cell (320), and the third oxidation-reduction cell (330) denotes an oxidation electrode part (anode part), and the part marked with (-) denotes 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).

[0078] The target solution storage unit (301) stores the electrolyte containing vanadium ions to be treated (hereinafter, the target solution). The counterpart solution storage unit (302) stores a counterpart solution (also called a buffer solution) containing vanadium ions. The target solution storage unit (301) and the counterpart solution storage unit (302) can each store an electrolyte containing vanadium ions having an oxidation number of 3.5.

[0079] The first oxidation-reduction cell (310) includes a first oxidation electrode unit (310a) and a first reduction electrode unit (310b). The first oxidation electrode unit (310a) is connected to a counter solution storage unit (302) and a counter solution is supplied thereto. The first reduction electrode unit (310b) is connected to a treatment target solution storage unit (301) and a treatment target solution is supplied thereto. Through the oxidation-reduction reaction in the first oxidation-reduction cell (310), vanadium ions in the treatment target solution of the reduction electrode unit (310b) can be reduced to an oxidation number of 2 to 3, and vanadium ions in the counter solution of the oxidation electrode unit (310a) can be oxidized to an oxidation number of 4 to 5. In this process, impurities contained in the treatment target solution of the reduction electrode unit (310b) can be removed from the treatment target solution by being adsorbed on the reduction electrode of the reduction electrode unit (310b).

[0080] The second oxidation-reduction cell (320) includes a second oxidation electrode unit (320a) and a second reduction electrode unit (320b). The second oxidation electrode unit (320a) is supplied with a solution to be treated from the first oxidation-reduction cell (310). The second reduction electrode unit (320b) is supplied with a solution to be treated from the third oxidation-reduction cell (330). Through the oxidation-reduction reaction of the second oxidation-reduction cell (320), vanadium ions in the solution to be treated in the reduction electrode unit (320b) and the oxidation electrode unit (320a) can be reduced and oxidized to an oxidation number of 3.5, respectively.

[0081] The third oxidation-reduction cell (330) includes a third oxidation electrode unit (330a) and a third reduction electrode unit (330b). The third oxidation electrode unit (330a) is supplied with a solution to be treated from the second oxidation electrode unit (320a) of the second oxidation-reduction cell. The third reduction electrode unit (330b) is supplied with a counter solution from the first oxidation electrode unit (310a) of the first oxidation-reduction cell (310). Through the oxidation-reduction reaction in the third oxidation-reduction cell (330), vanadium ions in the solution to be treated in the third oxidation electrode unit (330a) can be oxidized to an oxidation number of 4 to 5, and vanadium ions in the counter solution in the third reduction electrode unit (330b) can be reduced to an oxidation number of 3.5.

[0082] The solution to be treated is discharged from the second reduction electrode unit (320b) of the second oxidation-reduction cell and stored in the treated solution storage unit (301'). That is, the treated solution, which is discharged from the third oxidation electrode unit of the third oxidation-reduction cell and passes through the second reduction electrode unit of the second oxidation-reduction cell and has an oxidation number of 3.5, is stored in the treated solution storage unit (301'). The treated solution storage unit (301') may be the same as or different from the solution to be treated storage unit (301).

[0083] Meanwhile, each cell in which an oxidation-reduction reaction is performed may additionally include a device for monitoring the oxidation states of the solution to be treated and the corresponding solution. For this purpose, an OCV (Open Cell Voltage) meter or the like may be additionally placed in each cell in which an oxidation-reduction reaction is performed.

[0084] In addition, the device according to an embodiment of the present invention may additionally include a control unit (not shown) for controlling the voltage, current density, flow rate, etc. of each oxidation-reduction cell.

[0085] The first oxidation-reduction cell (310) can be controlled to apply a voltage of 1.5 V or less depending on the flow rate of the relative solution to remove impurities.

[0086] Meanwhile, the third oxidation-reduction cell (330) can be controlled to apply a voltage of 1.3 V or higher. In the case of the third oxidation-reduction cell, current density control is important. In order to minimize the change in the oxidation number of vanadium ions, the difference between the current density of the first oxidation-reduction cell (310) and the current density of the third oxidation-reduction cell should be 0.5 A / m. 2 It is preferable that the current density of the first oxidation-reduction cell and the current density of the third oxidation-reduction cell be controlled to be the same, and more preferably, the current density of the first oxidation-reduction cell and the current density of the third oxidation-reduction cell can be controlled to be the same.

[0087] The second oxidation-reduction cell can be controlled to apply various voltages, and in some cases, can be controlled to be maintained in a short-circuited state. Even if the wires of the oxidation electrode (anode) and reduction electrode (cathode) of the second oxidation-reduction cell are short-circuited, no pressure is generated, and an electrolyte having a desired target oxidation number can be produced. When the flow rates are the same, electrolyte production is possible simply by adjusting the voltages of cells 1 and 3. Meanwhile, the current density of the second oxidation-reduction cell can affect the processing efficiency of the third oxidation-reduction cell.

[0088]

[0089] Example

[0090] 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.

[0091]

[0092] Using the device illustrated in Fig. 3, a 3.5-valent vanadium ion-containing electrolyte (treatment target solution) was treated using a counter solution (3.5-valent vanadium ion-containing electrolyte). The first to third oxidation-reduction cells all had the same area.

[0093] In the treatment of an electrolyte containing vanadium ions, the generation of pressure was measured while changing the voltage and current density of the second oxidation-reduction cell and the third oxidation-reduction cell as shown in Table 1.

[0094] Whether pressure was generated and the degree of pressure increase was measured using the pressure measurement cell shown in Fig. 4.

[0095] The structure of the pressure measurement cell used in the experiment is shown in Fig. 4.

[0096] 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 (501) 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, and an injection amount of 138 g was used. An ion-selective separator was used as the separator. An aluminum collector was used as the metal collector. A carbon separator was used as the carbon collector. A Sensys product was used as the pressure gauge (550).

[0097] 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.

[0098] [Table 1]

[0099]

[0100] Referring to Table 1, impurity removal was achieved under the conditions of an applied voltage of 1.5 V and a flow rate of 1 L / h of the solution to be treated in the first oxidation-reduction cell (cell 1).

[0101] In the case of the second oxidation-reduction cell (cell 2), neither the voltage and current applied nor the short circuit state affected the removal of impurities.

[0102] In the case of the third oxidation-reduction cell (cell 3), a voltage of 1.3 V or higher was applied. Meanwhile, it can be seen that the smaller the difference between the current density of the first oxidation-reduction cell and the current density of the third oxidation-reduction cell (the first to third oxidation-reduction cells have the same area, and therefore the current difference between each cell), the closer the oxidation number of the final treated solution is to 3.5, which is the oxidation number of the initial target solution to be treated. In particular, in the case of samples 2 and 5 in which the current densities of the first oxidation-reduction cell and the third oxidation-reduction cell are the same, the oxidation number of the vanadium ion of the final treated solution was nearly 3.5.

[0103] After the vanadium (V)-containing treatment solution having an oxidation number of 3.5 was separately supplied to a charging cell and a voltage of 1.6 V was applied to remove metal impurities from the reduction electrode section, the process was repeated 3 times (Comparative Example 1) and 4 times (Comparative Example 2), and after the treatment according to Example 1 (Sample 1) was performed, the pressure measurement results are shown in Table 2 and Fig. 5. The total volume of the treatment solution of Comparative Examples 1 and 2 and Example 1 was the same at 2 L.

[0104] [Table 2]

[0105]

[0106] Referring to Table 2 and Figure 5, when comparing Comparative Example 1 and Comparative Example 2, pressure was generated in Comparative Example 1 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.

[0107] Additionally, in the case of Comparative Example 2, a voltage of 1.6 V was required, whereas in the case of Example 1, a voltage of 1.5 V was required. Operating the electrochemical cell at a low voltage reduces the risk of damage to the materials constituting the cell, which can extend the replacement cycle of components.

[0108] 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 supplying a treatment target solution containing vanadium ions to be treated to the reduction electrode section of the first oxidation-reduction cell, and supplying a counter solution containing vanadium ions to the oxidation electrode section of the first oxidation-reduction cell; (b) a step of reducing vanadium ions of the solution to be treated while oxidizing vanadium ions of the counter solution in the first oxidation-reduction cell; (c) a step of oxidizing vanadium ions of the treatment target solution supplied from the first oxidation-reduction cell in the second oxidation-reduction cell; and (d) a step of oxidizing vanadium ions of a solution to be treated supplied from the second oxidation-reduction cell in a third oxidation-reduction cell while reducing vanadium ions of a counter solution supplied from the first oxidation-reduction cell; A method for treating a vanadium ion-containing electrolyte, wherein vanadium ions of a treatment target solution supplied from the third oxidation-reduction cell in the step (c) are reduced.

2. In paragraph 1, A method for treating an electrolyte solution containing vanadium ions, wherein impurities contained in the solution to be treated are removed in the step (b) above.

3. In paragraph 1, A method for treating an electrolyte solution containing vanadium ions, wherein the vanadium ions of the solution to be treated in step (a) above have an oxidation number of 3.

5.

4. In paragraph 3, In the step (b) above, the vanadium ion of the solution to be treated is reduced to an oxidation number of 2 to 3, and the vanadium ion of the counter solution is oxidized to an oxidation number of 4 to 5. In the step (c) above, the vanadium ion of the solution to be treated supplied from the first oxidation-reduction cell is oxidized to an oxidation number of 3.5, and the vanadium ion of the solution to be treated supplied from the third oxidation-reduction cell is reduced to an oxidation number of 3.

5. A method for treating an electrolyte solution containing vanadium ions, wherein, in the step (d) above, vanadium ions of the treatment target solution supplied from the second oxidation-reduction cell are oxidized to an oxidation number of 4 to 5, and vanadium ions of the counter solution supplied from the first oxidation-reduction cell are reduced to an oxidation number of 3.

5.

5. In paragraph 1, In the step (b) above, a voltage of 1.5 V or less is applied to the first oxidation-reduction cell, A method for treating an electrolyte containing vanadium ions, wherein in the step (d) above, a voltage of 1.3 V or higher is applied to the third oxidation-reduction cell.

6. In paragraph 5, The difference between the current density of the first oxidation-reduction cell and the current density of the third oxidation-reduction cell is 0.5 A / m 2 Below, a method for treating an electrolyte containing vanadium ions.

7. In paragraph 1, A method for treating an electrolyte containing vanadium ions, wherein the applied voltage or current density of the third oxidation-reduction cell is controlled according to the required oxidation number of the solution to be treated.

8. In paragraph 1, A method for treating a vanadium ion-containing electrolyte, which further comprises the step of supplying a vanadium ion-containing electrolyte for refreshing to the first oxidation-reduction cell after recovering the treated solution through steps (b) to (d) and applying a reverse voltage opposite to the polarity of the voltage applied in step (b) to desorb impurities adsorbed on the reduction electrode with the vanadium ion-containing electrolyte for refreshing.

9. A treatment solution storage unit for storing a treatment solution, which is an electrolyte containing vanadium ions to be treated; A counter solution storage unit for storing a counter solution containing vanadium ions; A first oxidation-reduction cell including a first reduction electrode section connected to the processing target solution storage section and supplied with the processing target solution, and a first oxidation electrode section connected to the counter solution storage section and supplied with the counter solution; A second oxidation-reduction cell including a second oxidation electrode section to which a solution to be treated is supplied from the first oxidation-reduction cell, and a second reduction electrode section to which a solution to be treated is supplied from the third oxidation-reduction cell; and A device for treating a vanadium ion-containing electrolyte, comprising a third oxidation-reduction cell including a third oxidation electrode section to which a treatment target solution is supplied from the second oxidation-reduction cell, and a third reduction electrode section to which a counter solution is supplied from the first oxidation-reduction cell.

10. In paragraph 9, A device for treating a vanadium ion-containing electrolyte, wherein the treated solution is discharged from the second reduction electrode section of the second oxidation-reduction cell.

11. In paragraph 9, A device for treating a vanadium ion-containing electrolyte, wherein the above-described treatment target solution storage unit and the above-described counterpart solution storage unit each store an electrolyte containing vanadium ions having an oxidation number of 3.

5.

12. In paragraph 11, In the above first oxidation-reduction cell, vanadium ions of the target solution of the reduction electrode section are reduced to an oxidation number of 2 to 3, and vanadium ions of the counter solution of the oxidation electrode section are oxidized to an oxidation number of 4 to 5. In the second oxidation-reduction cell, vanadium ions of the target solution in the reduction electrode section and the oxidation electrode section are reduced and oxidized to an oxidation number of 3.5, respectively. A device for treating an electrolyte containing vanadium ions, wherein in the third oxidation-reduction cell, vanadium ions of a solution to be treated in an oxidation electrode section are oxidized to an oxidation number of 4 to 5, and vanadium ions of a counter solution in a reduction electrode section are reduced to an oxidation number of 3.

5.

13. In paragraph 9, A voltage of 1.5 V or less is applied to the first oxidation-reduction cell, A device for treating a vanadium ion-containing electrolyte, wherein a voltage of 1.3 V or higher is applied to the third oxidation-reduction cell.

14. In paragraph 13, The difference between the current density of the first oxidation-reduction cell and the current density of the third oxidation-reduction cell is 0.5 A / m 2 Below, a device for processing an electrolyte containing vanadium ions.

15. In paragraph 9, A device for treating a vanadium ion-containing electrolyte, wherein the applied voltage or current density of the third oxidation-reduction cell is controlled according to the required oxidation number value of the solution to be treated.

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