Device for manufacturing vanadium ion-containing liquid electrode by direct injection of reducing agent, and method for manufacturing vanadium ion-containing liquid electrode by using same

Abstract

The present invention relates to a device for manufacturing a vanadium ion-containing liquid electrode by direct injection of a reducing agent, and a method for manufacturing a vanadium ion-containing liquid electrode by using same. The device for manufacturing a vanadium ion-containing liquid electrode comprises: a liquid electrode storage unit; an electrochemical processing unit including a cathode unit and an anode unit; a cathode unit supply line for connecting the liquid electrode storage unit and an inlet of the cathode unit, and an anode unit supply line for connecting the liquid electrode storage unit and an inlet of the anode unit; a cathode unit recovery line connected to an outlet of the cathode unit and an anode unit recovery line connected to an outlet of the anode unit; and a reducing agent supply unit for storing a liquid reducing agent and directly supplying the liquid reducing agent to the cathode unit through the cathode unit supply line.

Description

Apparatus for manufacturing a vanadium ion-containing liquid electrode with direct injection of a reducing agent and a method for manufacturing a vanadium ion-containing liquid electrode using the same

[0001] The present invention relates to a manufacturing technology for a vanadium ion-containing liquid electrode. More specifically, it relates to an apparatus and method for manufacturing a vanadium ion-containing liquid electrode that can remove impurities contained in the liquid electrode without leaving any excess liquid electrode by using a reducing agent and an electrochemical reaction.

[0002] Vanadium ion batteries (VIBs) or vanadium redox flow batteries (VRFBs) utilize a liquid electrode containing vanadium ions. Here, the liquid electrode may be referred to as a liquid electrolyte in that it performs the role of an electrolyte, but it is more preferable to refer to it as a liquid electrode because it participates in oxidation-reduction reactions in addition to its role as an electrolyte. When applied to secondary batteries, the liquid electrode containing vanadium ions offers the advantage of high safety against explosions, fires, etc. Furthermore, the liquid electrode containing vanadium ions has the advantages of a long lifespan and high capacity, and is cost-effective as the liquid electrode can be separated and reused through the electrochemical reactions of charging and discharging the secondary battery.

[0003] The liquid electrodes containing vanadium ions used in the anode (also called the oxidation electrode) and the cathode (also called the reduction electrode) require vanadium ions with oxidation numbers of, for example, tetravalent (4+) in the anode and trivalent (3+) in the cathode based on the full discharge state, and vanadium ions with oxidation numbers of pentavalent (5+) in the anode and divalent (2+) in the cathode based on the full charge state. The charge-discharge reaction occurs as the oxidation number of the vanadium active material changes, and in order for an electrochemical reversible reaction to occur, it is important to manufacture the liquid electrodes of the anode and the cathode with matching oxidation numbers.

[0004] Generally, as a vanadium ion-containing liquid electrode, a liquid electrode with an average oxidation number of vanadium ions of 3.5 (3.5+) that can be used commonly for the liquid electrode supplied to the cathode and the liquid electrode supplied to the anode has been used.

[0005] A typical method for manufacturing a 3.5-valent vanadium liquid electrode involves mixing V2O5 powder with a sulfuric acid solution and adding a reducing agent to produce a 4-valent vanadium liquid electrode, then using electrolysis to produce a 3-valent liquid electrode, and mixing this with the 4-valent liquid electrode for use. Through electrolysis, the liquid electrode at the anode is oxidized from 4 to 5, and the liquid electrode at the cathode is reduced from 4 to 3.

[0006] A liquid electrode reduced to trivalent can be used by mixing it with a tetravalent liquid electrode and adjusting the vanadium ion concentration. However, since a pentavalent liquid electrode cannot be used as is, it must be manufactured back into a trivalent liquid electrode through a process of reduction by a reducing agent and electrolysis, and then mixed with a tetravalent liquid electrode and adjusted for vanadium ion concentration to form an average 3.5-valent vanadium liquid electrode. To increase the production volume of the average 3.5-valent liquid electrode, multiple tanks are required for these reduction, electrolysis, and vanadium ion concentration adjustment processes. However, the use of such multiple tanks presents problems such as increased manufacturing time and higher costs.

[0007] Published Patent Application No. 10-2022-0075650 (June 8, 2022, hereinafter, Patent Document 1) provides a method for manufacturing an electrolyte for a vanadium redox flow battery, which can continuously produce an electrolyte by reusing a surplus pentavalent vanadium ion solution.

[0008] According to the above patent document 1, a first vanadium ion solution is introduced into a first anode electrolyte tank and a first cathode electrolyte tank, the first vanadium ion solution introduced into the anode is oxidized to produce a second vanadium ion solution, the first vanadium ion solution introduced into the cathode is reduced to produce a third vanadium ion solution, and the second vanadium ion solution reacts with a reducing agent in a reduction reaction tank to be reduced to a fourth vanadium ion solution. Subsequently, the produced fourth vanadium ion solution is introduced into a second anode electrolyte tank and a second cathode electrolyte tank (170), and an oxidation-reduction reaction is performed again.

[0009] In this way, conventionally, a method of reusing excess pentavalent vanadium ion solution by passing it through several tanks is used.

[0010] Furthermore, for VRFB or VIB, the presence of impurities in the liquid electrode reduces battery life due to hydrogen generation at the cathode. Therefore, once the manufacturing of the liquid electrode is complete, an additional process is required to remove impurities.

[0011] To remove metal impurities, methods using extractants are mainly used. Figure 1 schematically shows an apparatus for extracting and removing metal impurities using a general extractant.

[0012] Referring to FIG. 1, a vanadium (V)-containing liquid electrode having an oxidation state of 3.5 is continuously supplied from a liquid electrode storage unit (101) in which the vanadium-containing liquid electrode is stored to an extraction device (110) containing an organic phase including kerosene and an extractant. The extraction device (110) includes an organic phase (112), a heating device (115) for providing a reaction temperature, and a stirrer (116) for even mixing. As the vanadium-containing liquid electrode passes through the organic phase, impurities contained in the vanadium-containing liquid electrode move into the organic phase, forming a treated vanadium-containing liquid electrode (114). The vanadium-containing liquid electrode from which impurities have been removed is recovered to the liquid electrode storage unit (102).

[0013] At this time, the reaction temperature for removing impurities using an extractant is 40°C or higher, and a heating device (115) is essential for this. Since the use of a heating device is generally energy-consuming, it is necessary to improve it.

[0014] The problem that the present invention aims to solve is to provide a vanadium ion liquid electrode manufacturing apparatus and method that can shorten the reaction time for manufacturing a liquid electrode having a desired average oxidation number.

[0015] In addition, the problem that the present invention aims to solve is to provide an apparatus and method for manufacturing a vanadium ion liquid electrode that can effectively remove impurities from a vanadium ion-containing liquid electrode without any separate impurity removal process and without any excess liquid electrode substantially existing.

[0016] The objectives of the present invention are not limited to the purposes mentioned above, and other unmentioned objectives will be clearly understood by those skilled in the art from the description below.

[0017] A vanadium ion-containing liquid electrode manufacturing device according to one embodiment of the present invention for solving the above problem comprises: a liquid electrode storage unit; an electrochemical processing unit including an anode and a cathode; an anode supply line connecting the liquid electrode storage unit and the inlet of the anode and a cathode supply line connecting the liquid electrode storage unit and the inlet of the cathode; an anode recovery line connected to the outlet of the anode and a cathode recovery line connected to the outlet of the cathode; and a reducing agent supply unit storing a liquid reducing agent and directly supplying the liquid reducing agent to the anode through the anode supply line.

[0018] In some embodiments, an electrochemical reduction reaction of the first liquid electrode is performed at the cathode of the electrochemical treatment unit while impurities contained in the first liquid electrode are removed, and an oxidation reaction of the reducing agent can be performed at the anode of the electrochemical treatment unit.

[0019] In some embodiments, an electrochemical oxidation reaction of the first liquid electrode and a reduction reaction by the reducing agent may be performed at the anode portion of the electrochemical treatment unit.

[0020] In some embodiments, the electrochemical oxidation reaction of the reducing agent may be performed at the anode portion of the electrochemical treatment unit.

[0021] In some embodiments, the anode recovery line and the cathode recovery line may be connected to the liquid electrode storage unit.

[0022] In some embodiments, the reducing agent supply unit may include a syringe pump.

[0023] A method for manufacturing a vanadium ion-containing liquid electrode according to an embodiment of the present invention for solving the above problem comprises: (a) supplying a first liquid electrode containing a first vanadium ion stored in a liquid electrode storage unit to the anode and cathode of an electrochemical treatment unit, respectively, through an anode supply line and a cathode supply line; (b) supplying a liquid reducing agent from a reducing agent supply unit connected to the anode supply line to the anode supply line so that the first liquid electrode and the reducing agent are supplied together to the anode; (c) performing an electrochemical reduction reaction of the first liquid electrode at the cathode of the electrochemical treatment unit and performing an oxidation reaction of the reducing agent at the anode of the electrochemical treatment unit; (d) mixing the first liquid electrode that has passed through the anode and the first liquid electrode that has passed through the cathode to form a second liquid electrode containing a second vanadium ion; and (e) recovering the second liquid electrode.

[0024] In some embodiments, the reducing agent may include one or more of formic acid, formaldehyde, methanol, ethanol, oxalic acid, and ammonium hydroxide.

[0025] In some embodiments, an electrochemical oxidation reaction of the first liquid electrode and a reduction reaction by the reducing agent may be performed at the anode portion of the electrochemical treatment unit.

[0026] In some embodiments, the electrochemical oxidation reaction of the reducing agent may be performed at the anode portion of the electrochemical treatment unit.

[0027] In some embodiments, in step (c), the average oxidation number of the vanadium ions of the first liquid electrode is lowered as it passes through the cathode, and the average oxidation number of the vanadium ions of the first liquid electrode is maintained or increased to less than 1 as it passes through the anode.

[0028] In some embodiments, in step (a), the vanadium ions of the first liquid electrode have an average oxidation number of 4 to 5, and in step (d), the vanadium ions of the second liquid electrode may have an average oxidation number lower than that of the vanadium ions of the first liquid electrode.

[0029] In some embodiments, the average oxidation number of the second liquid electrode may be 3.0 to 3.7.

[0030] In some embodiments, the first liquid electrode passing through the cathode portion contains trivalent vanadium ions (V 3+ ) including, and the first liquid electrode that has passed through the anode part contains tetravalent vanadium ions (V 4+ ) including, or the first liquid electrode that has passed through the cathode part contains divalent vanadium ions (V 2+ ) including, and the first liquid electrode that has passed through the anode part contains pentavalent vanadium ions (V 5+ It may include ).

[0031] In some embodiments, in step (c), impurities contained in the first liquid electrode at the cathode may be removed.

[0032] In some embodiments, the amount (L) of the reducing agent may be determined within a 10% error range of the value determined by the following Equation 1 according to the target oxidation number value.

[0033] [Equation 1]

[0034] Target oxidation number value = X - (c*d*e) / (a*b)

[0035] (In Equation 1, X is the oxidation number of the first liquid electrode, a is the molar concentration of vanadium ions (M), b is the amount of liquid electrode (L), c is the molar concentration of the reducing agent (M), d is the amount of reducing agent used (L), and e is the number of electron donors of the reducing agent)

[0036] According to the apparatus and method for manufacturing a vanadium ion-containing liquid electrode according to one embodiment of the present invention, impurities in the vanadium ion-containing liquid electrode can be effectively removed using a reducing agent and an electrochemical reaction, while substantially eliminating excess liquid electrodes. In particular, in the case of the present invention, by directly injecting a liquid reducing agent into the anode of the electrochemical treatment unit, the target oxidation state of the liquid electrode can be reached in a single reaction, thereby significantly reducing the liquid electrode manufacturing time compared to conventional methods.

[0037] In addition, the method for manufacturing a vanadium ion-containing liquid electrode according to one embodiment of the present invention can easily manufacture a vanadium ion-containing liquid electrode having a target oxidation state value from which impurities have been removed by controlling the amount of reducing agent and controlling the process conditions of the electrochemical treatment unit.

[0038] In addition, the method for manufacturing a vanadium ion-containing liquid electrode according to one embodiment of the present invention can suppress changes in the concentration of vanadium and sulfuric acid.

[0039] In addition, the method for manufacturing a vanadium ion-containing liquid electrode according to one embodiment of the present invention can be implemented as a continuous process.

[0040] The effects of the present invention are not limited to those mentioned above, and other unmentioned effects will be clearly understood by those skilled in the art from the description in the claims.

[0041] Figure 1 schematically shows an apparatus for removing metal impurities using a general extractant.

[0042] FIG. 2 schematically illustrates a method for manufacturing a vanadium ion-containing liquid electrode according to an embodiment of the present invention.

[0043] FIG. 3 schematically shows a vanadium ion-containing liquid electrode manufacturing apparatus according to an embodiment of the present invention.

[0044] <Explanation of Symbols>

[0045] 301: Supply line

[0046] 301a: Anode supply line

[0047] 301b: Cathode supply line

[0048] 302 : Recovery Line

[0049] 302a: Anode recovery line

[0050] 302b : Cathode recovery line

[0051] 310: Liquid electrode storage unit

[0052] 320 : Electrochemical treatment unit

[0053] 321 : Bipolar part

[0054] 322 : Negative electrode

[0055] 323 : Separator

[0056] 330 : Reducing agent supply unit

[0057] 340 : Pump

[0058] The advantages and features of the present invention and the methods for achieving them will become clear by referring to the embodiments described below in detail together with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below but may be implemented in various different forms. These embodiments are provided merely 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. Throughout the specification, the same reference numerals refer to the same components.

[0059] In describing this specification, if it is determined that a detailed description of related prior art could unnecessarily obscure the gist of this specification, such detailed description is omitted.

[0060] Although terms such as "first," "second," etc. are used in this specification to describe various components, it should be understood that these components are not limited by these terms. These terms are used merely to distinguish one component from another, and unless specifically stated otherwise, the first component may be the second component.

[0061] Throughout this specification, unless specifically stated otherwise, each component may be singular or plural.

[0062] In interpreting the components in this specification, they are interpreted to include an error range even if there is no separate explicit description.

[0063] In this specification, the statement that any component is placed on the "upper (or lower)" or "upper (or lower)" of a component means not only that any component is placed in contact with the upper (or lower) surface of said component, but also that another component may be interposed between said component and any component placed on (or under) said component. Where it is stated in this specification that any component is "connected," "coupled," or "connected" to another component, it should be understood that said components may be directly connected or connected to each other, but that another component may be "interposed" between each component, or that each component may be "connected," "coupled," or "connected" through another component. Where terms such as "comprising," "having," "consisting of," "placed," or "possessing" are used for a component in this specification, other parts may be added unless "only" is used. Where a component is expressed in the singular, it includes cases where it is included in the plural unless specifically stated otherwise. Throughout this specification, "A and / or B" means A, B, or A and B unless specifically stated otherwise, and "C to D" means C or more and D or less unless specifically stated otherwise.

[0064] Unless otherwise specifically stated in this specification, the standard of any unit is interpreted to mean "weight."

[0065] In this specification, unless otherwise specifically stated, "vanadium ion-containing liquid electrode" is interpreted to refer to the same object as "vanadium ion liquid electrode," "liquid electrode using (utilizing) vanadium ions," "liquid electrode containing vanadium ions," "vanadium liquid electrode," "liquid electrode containing vanadium active material," etc.

[0066] In this specification, the oxidation number of vanadium ions of a vanadium ion-containing liquid electrode (briefly referred to as the oxidation number of the liquid electrode) may be the average value of the oxidation number of the liquid electrode itself at the time of manufacturing or supply, or the oxidation number of vanadium ions of the liquid electrode supplied to the positive and negative electrodes, and may represent the average value of the oxidation number of vanadium ions of the positive liquid electrode and the negative liquid electrode when the secondary battery is driven by charging and discharging.

[0067] In this specification, the cathode is an electrode in which the oxidation number of vanadium ions is lowered as a reduction reaction takes place, and may be referred to as the reduction electrode. In this specification, the anode is an electrode in which the oxidation number of vanadium ions is raised as an oxidation reaction takes place, and may be referred to as the oxidation electrode. However, as will be described later, in the present invention, there is no substantial change in the oxidation number value of vanadium ions in the anode due to the presence of a reducing agent.

[0068]

[0069] FIG. 2 schematically illustrates a method for manufacturing a vanadium ion-containing liquid electrode according to an embodiment of the present invention. FIG. 3 schematically illustrates an apparatus for manufacturing a vanadium ion-containing liquid electrode according to an embodiment of the present invention.

[0070] Referring to FIG. 2, a method for manufacturing a vanadium ion-containing liquid electrode according to one embodiment of the present invention includes a first liquid electrode supply step (S210), a reducing agent supply step (S220), an electrochemical treatment step (S230), a second liquid electrode formation step (S240), and a second liquid electrode recovery step (S250).

[0071] In the first liquid electrode supply step (S210), a first liquid electrode containing a first vanadium ion is supplied from the liquid electrode storage unit (310) to the electrochemical treatment unit (320) through the supply line (301).

[0072] The first liquid electrode refers to a first vanadium ion-containing liquid electrode, and in the present invention, the first vanadium ion may be a pentavalent or tetravalent vanadium ion.

[0073] For example, the first vanadium ion-containing liquid electrode comprises vanadium ions and an acidic solution. The vanadium ions may be supplied by vanadium oxide and may include one or more selected from the group consisting of, for example, V2O5, VOSO4, V2O3, NH4VO3, and V2O4, but are not necessarily limited thereto, and may be selected according to the liquid electrode production conditions, target production 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, or for example, 2 M to 5 M, but is not necessarily limited thereto, and may be appropriately adjusted according to the type of acidic solution selected, etc. The concentration of vanadium ions in the first vanadium ion-containing liquid electrode may be 1.5 M to 3.7 M.

[0074] The first vanadium ion-containing liquid electrode can be prepared as a pentavalent vanadium ion-containing liquid electrode by mixing V2O5, H2SO4, and H2O and stirring at a temperature of 80 to 90°C for at least 12 hours. Subsequently, a reducing agent can be added to the pentavalent vanadium ion-containing liquid electrode to prepare a tetravalent vanadium ion-containing liquid electrode.

[0075] Specifically, the first vanadium ion-containing liquid electrode is supplied to the anode (321) of the electrochemical treatment unit (320) through the anode supply line (301a) branched from the supply line (301), and to the cathode (322) of the electrochemical treatment unit (320) through the cathode supply line (301b) branched from the supply line (301).

[0076] Next, in the reducing agent supply step (S220), a liquid first reducing agent is supplied from a reducing agent supply unit (330) connected to the anode supply line (301a) to the anode (321) of the electrochemical treatment unit (320) through the anode supply line (301a). The reducing agent can be activated when voltage is applied at the anode (321) of the electrochemical treatment unit (320).

[0077] By supplying a reducing agent to the anode supply line (301a), the first reducing agent and the first liquid electrode are supplied together to the anode (321) of the electrochemical treatment unit (320). Then, only the first liquid electrode is supplied to the cathode (322) of the electrochemical treatment unit (320).

[0078] The first reducing agent may include one or more of liquid formic acid, formaldehyde, methanol, ethanol, ammonium hydroxide, and solid oxalic acid (used after dissolving in water or in a liquid electrode containing the first vanadium ion), and it is more preferable that it be formic acid. If necessary, the first reducing agent may be supplied together with water.

[0079] The amount of the above reducing agent used may be determined within a 10% error range from the value determined by Formula 1 below, depending on the target oxidation number value. The target oxidation number value may be set to a value of 3.0 to 4.0 depending on the application, and preferably to a value of 3.0 to 3.8. More preferably, the target oxidation number value may be set to a value of 3.45 to 3.75, and most preferably to a value of 3.55 to 3.65.

[0080] [Equation 1]

[0081] Target oxidation number value = X - (c*d*e) / (a*b)

[0082] (In Equation 1, X is the oxidation number of the first liquid electrode, a is the molar concentration of vanadium ions (M), b is the amount of liquid electrode (L), c is the molar concentration of the reducing agent (M), d is the amount of reducing agent used (L), and e is the number of electron donors of the reducing agent)

[0083] Next, the electrochemical treatment step (S230) is performed in an electrochemical treatment unit (320) comprising an anode (321) and a cathode (322). In the anode (431) of the electrochemical treatment unit, an electrochemical oxidation reaction of the first liquid electrode and a reduction reaction by the reducing agent, or an electrochemical oxidation reaction of the reducing agent, are performed, and in the cathode (322) of the electrochemical treatment unit, an electrochemical reduction reaction of the first liquid electrode is performed.

[0084] Meanwhile, an oxidation reaction of a reducing agent is performed in the anode (321). For example, as vanadium ions are oxidized by an electrochemical oxidation reaction and reduced by a reduction reaction with a reducing agent, the average oxidation number of the vanadium ions may be maintained or increased to less than 1, for example, less than 0.5, less than 0.3, or less than 0.1. For example, tetravalent vanadium ions may be oxidized to pentavalent in the anode, but in the case of the present invention, due to the presence of a reducing agent, the vanadium ions are reduced again by the reducing agent along with the oxidation of the vanadium ions, so that the average oxidation number of the vanadium ions of the first liquid electrode that passed through the anode may be maintained at 4, or even if increased, the average oxidation number may be less than 5.

[0085] In addition, the oxidation number of vanadium ions may be maintained as the reducing agent is oxidized instead by an electrochemical oxidation reaction at the anode (321).

[0086] For example, if the reducing agent is formic acid, the oxidation reaction of formic acid may be as follows.

[0087] HCOOH → CO2 + 2H + + 2e -

[0088] The tetravalent or pentavalent vanadium ions of the first liquid electrode can be reduced to divalent or trivalent vanadium ions as they pass through the cathode (322).

[0089] For example, the first liquid electrode that passes through the cathode (322) contains trivalent vanadium ions (V 3+ The first liquid electrode that passes through the anode (321) contains ) and contains tetravalent vanadium ions (V 4+ It may include ).

[0090] As another example, the first liquid electrode that passed through the cathode (322) contains divalent vanadium ions (V 2+ The first liquid electrode that passes through the anode (321) contains ) and contains pentavalent vanadium ions (V 5+ It may include ).

[0091] The first vanadium ion-containing liquid electrode is supplied separately to the anode (321) and the cathode (322), and after passing through the anode (321) and the cathode (322) respectively, it can be combined to form a second vanadium ion-containing liquid electrode (S240).

[0092] The first liquid electrode and reducing agent can be moved from the liquid electrode storage unit (310) to the electrochemical processing unit (320) via the supply line (301). A pump (340) may be placed to facilitate the supply of the first liquid electrode and reducing agent to the electrochemical processing unit (320). FIG. 3 shows an example in which a pump (340) is placed at the front of the anode (321) and the cathode (322), respectively, after the supply line (301) is branched.

[0093] The electrochemical treatment unit (320) includes an anode (321) and a cathode (322), and a separator (323) may also be included between the anode (321) and the cathode (322). The anode (321) or the cathode (322) may include a solid electrode such as carbon felt.

[0094] The electrochemical treatment unit (320) can remove impurities by charging the first vanadium ion-containing liquid electrode.

[0095] Meanwhile, in the anode (321), vanadium ions can be reduced by a reducing agent while being oxidized. For example, tetravalent vanadium ions can be oxidized to pentavalent in the anode. In the case of the present invention, due to the presence of a reducing agent, vanadium ions are reduced by the reducing agent along with the oxidation of vanadium ions; thus, tetravalent vanadium ions can be oxidized to pentavalent in the anode and reduced to tetravalent by the reducing agent. In particular, in the case of the present invention, a liquid reducing agent is directly injected into the anode (321). By suppressing the supply of the reducing agent to the cathode (322) through this, the reduction reaction time by the reducing agent can be significantly shortened compared to the case where the reducing agent is included in the first liquid electrode and only half of the reducing agent participates in the anode reduction reaction per cycle. Therefore, in the case of the present invention, a liquid electrode having a target oxidation number can be manufactured in a single reaction cycle in the electrochemical treatment unit.

[0096] The tetravalent vanadium ions can be reduced to divalent or trivalent vanadium ions as they pass through the cathode (322). At this time, impurities contained in the first liquid electrode can be removed at the cathode (322).

[0097] The principle of removing impurities utilizes the principle that when the oxidation number of vanadium ions in the liquid electrode at the cathode is lower than the oxidation number of metal impurities during the charging reaction in the electrochemical treatment unit (320), metal impurities are precipitated (adsorbed) from the liquid electrode solution to the surface of the solid electrode (e.g., carbon felt) of the cathode. That is, when a liquid electrode containing vanadium and metal impurities is subjected to a reduction reaction in the cathode (322) of the electrochemical treatment unit (320), the average oxidation number of vanadium ions is lowered to a value of 2 to 4, preferably 2 to 3, and metal impurities are precipitated, i.e., adsorbed, on the electrode. By this principle, metal impurities are removed from the vanadium-containing liquid electrode, and the concentration of metal impurities in the vanadium-containing liquid electrode can be lowered.

[0098] Impurities that can be removed through the electrochemical treatment described above may include Fe, Co, Ni, Cu, Ge, Se, Mo, Ru, Rh, Pd, Ag, Cd, In, Sn, Sb, Te, W, Re, Os, Ir, Pt, Au, Tl, Pb, Bi, etc.

[0099] The flow rate of the first liquid electrode supplied from each pump (340) may be 2 L / h or less, more preferably 1 L / h or less. If the flow rate of the first liquid electrode is relatively small, the flow rate is slow, so the reaction time per cycle becomes relatively long, and accordingly, the reaction between the liquid electrode and the reducing agent can occur sufficiently, so the total number of cycles can be reduced. On the other hand, if the flow rate of the liquid electrode is relatively large, the flow rate is fast, so the reaction time per cycle becomes relatively short, and accordingly, the reaction between the liquid electrode and the reducing agent occurs relatively less, so it is necessary to increase the total number of cycles.

[0100] When the voltage applied to the electrochemical treatment unit is low, the potential difference between the voltage applied to the anode and cathode of the electrochemical treatment unit decreases, thereby reducing the effect of removing impurities; therefore, it is desirable that the voltage applied to the electrochemical treatment unit be 1.50 V or higher. When the applied voltage is less than 1.50 V, the probability of pressure-generating impurities being adsorbed onto the carbon felt decreases, and when a voltage between 1.50 and 1.55 V is applied, the single-pot process is not interrupted and pressure-generating impurities can be adsorbed onto the carbon felt.

[0101] More preferably, when the pump flow rate is 0.5 L / h or less, the voltage may be 1.50 V or higher, and when the pump flow rate is greater than 0.5 L / h and less than or equal to 2 L / h, the voltage may be 1.55 V or higher. The maximum value of the applied voltage may vary depending on the self-resistance of the carbon electrodes of the anode or cathode of the electrochemical treatment unit. In one embodiment of the present invention, when the voltage is 1.6 V or higher, there may be difficulties in the process due to the water splitting reaction in the electrochemical treatment unit; therefore, when the self-resistance of the carbon electrodes of the electrochemical treatment unit is low, it is more preferable to keep the voltage below 1.60 V.

[0102] Next, in the second liquid electrode formation step (S230), the first liquid electrode that passed through the anode (321) and the first liquid electrode that passed through the cathode (322) are mixed to form a second liquid electrode containing second vanadium ions. At this time, the average oxidation number value of the second liquid electrode is lower than the average oxidation number value of the first liquid electrode. In the present invention, the average oxidation number of the first liquid electrode may be 5 or 4. In the electrochemical treatment step (S220), the average oxidation number of the first liquid electrode that passed through the cathode is lowered, and the average oxidation number of the first liquid electrode that passed through the anode may be maintained. Thus, the second liquid electrode formed by mixing each first liquid electrode that passed through the cathode and anode has an oxidation number lower than the oxidation number of the first liquid electrode.

[0103] Next, in the second liquid electrode recovery step (S250), the second vanadium ion-containing liquid electrode is recovered to the first liquid electrode storage unit (310) or a separate liquid electrode storage unit. Specifically, the second vanadium ion-containing liquid electrode can be recovered through an anode recovery line (302a) connected to the anode (321) and a cathode recovery line (302b) connected to the cathode (322). FIG. 3 shows an example in which the second vanadium ion-containing liquid electrode is recovered to the liquid electrode storage unit (310) through the recovery line (302).

[0104] In the present invention, through the aforementioned processes, a first liquid electrode containing pentavalent or tetravalent vanadium ions can be converted to a second oxidation number with a reduced average oxidation number. A second liquid electrode containing second vanadium ions can have a target average oxidation number, such as, for example, trivalent or 3.5valent.

[0105] According to a method for manufacturing a vanadium ion-containing liquid electrode according to one embodiment of the present invention, a liquid electrode having a desired oxidation state can be manufactured with almost no excess liquid electrode amount by using a reducing agent and an electrochemical reaction, and furthermore, impurities in the vanadium ion-containing liquid electrode can be effectively removed. In particular, in the case of the present invention, since the reducing agent is directly injected into the anode of the electrochemical treatment unit, the average oxidation state of the target liquid electrode can be reached in a single reaction, and accordingly, the reaction time can be significantly shortened.

[0106] In addition, the method for manufacturing a vanadium ion-containing liquid electrode according to one embodiment of the present invention can be implemented as a continuous process.

[0107] In addition, the method for manufacturing a vanadium ion-containing liquid electrode according to one embodiment of the present invention can suppress changes in the concentration of vanadium and sulfuric acid. In the conventional case, since multiple tanks are used and the concentration of vanadium ions changes as they pass through each tank, a process of controlling the ion concentration for the manufactured liquid electrode is essential. However, in the case of the present invention, since the manufacturing and recovery of the vanadium ion-containing liquid electrode can be carried out in the same tank, or the storage of the liquid electrode passing through the anode and cathode sections of the electrochemical treatment unit can be carried out in the same tank, additional tanks required in conventional liquid electrode manufacturing technology are not required, and since the concentrations of vanadium and sulfuric acid do not change, there is an advantage of not requiring a separate step for controlling the concentration of vanadium ions.

[0108] Examples

[0109] The present invention will be explained in more detail below by describing experimental examples. However, this is merely one embodiment of the present invention, and the present invention is not limited thereto.

[0110] In the following examples, the oxidation number of vanadium ions was measured by ultraviolet visible spectrometry (UV) using a UV-Visible instrument (V-660, manufactured by JASCO).

[0111] Table 1 shows the final oxidation state of the liquid electrode according to pump flow rate and voltage control.

[0112] In Table 1, the liquid electrode concentration, i.e., the vanadium concentration (M), was set to 1.7M, the initial vanadium ion oxidation number of the liquid electrode was set to 4.0, and the amount of the liquid electrode was controlled to 1L. In addition, the pump flow rate (L / h) was set to 1L / h.

[0113] The formic acid information used is as follows.

[0114] Linear Formula: HCOOH / CH2O2

[0115] Assay: 85%

[0116] Molecular Weight (g / mol): 46.03

[0117] Density (g / cm 3 ): 1.22

[0118] Molar concentration of stock formic acid: (Density * Assay / 100) / Molecular weight * 1000 = 22.52 M

[0119] The final calculated oxidation number was set to 4-(c*d*e) / (a*b).

[0120] a : Vanadium molar concentration (M)

[0121] b: Amount of liquid electrode (L)

[0122] c : Molar concentration of reducing agent (M)

[0123] d : Amount of reducing agent (L)

[0124] e : Reducing agent electron donation number

[0125] If all the reducing agent has reacted, the final oxidation number measured by the UV-Vis instrument will be nearly identical to the calculated oxidation number.

[0126] [Table 1]

[0127]

[0128] Referring to Table 1, when the oxidation number is calculated using the above formula, it can be seen that for Examples 1 to 4, the results are very close to the final oxidation number values ​​measured using UV-Vis equipment. This can be attributed to the fact that almost all of the reducing agent reacted to correspond to the desired oxidation number. However, in the case of the comparative examples, there is a difference between the oxidation number and the final measured oxidation number. This can be attributed to the fact that the reducing agent was not fully consumed in the comparative examples.

[0129] In addition, using the above formula, the amount of reducing agent (L) can be derived according to the target oxidation number of the final liquid electrode. For example, if the target oxidation number of the final liquid electrode is set to 3.5,

[0130] The above formula is 3.5=4-(22.4*d*2) / (1.7*1),

[0131] d = 0.019L (19mL) and,

[0132] Accordingly, 19 mL of the required 22.4 M reducing agent can be obtained.

[0133] When comparing Example 1 and Comparative Example 1, Comparative Example 1 has a faster reducing agent flow rate compared to Example 1, so the reducing agent does not fully react, and the oxidation number of the final liquid electrode can be seen to be higher than that of Example 1.

[0134] In addition, when comparing Example 1 and Comparative Example 2, Comparative Example 2 has a voltage 0.05 V lower than Example 1, so the current is low, and as a result, it can be seen that not all of the reducing agent reacted. However, when comparing Example 1 and Example 4, if the flow rate of the syringe pump is slowed down sufficiently, the target oxidation number can be reached.

[0135] In addition, when comparing Comparative Example 3 and Example 4, it can be seen that even though a higher voltage was applied in Comparative Example 3, the oxidation number of the final liquid electrode is higher in Comparative Example 3, where the liquid electrode and the reducing agent were supplied together without a syringe pump, compared to Example 4, where the reducing agent was supplied directly to the anode.

[0136] In addition, according to Examples 1 to 4, results can be obtained that the syringe pump flow rate needs to be adjusted so that the amount of reducing agent used / syringe pump flow rate is 1 to 3 under a voltage condition of 1.55 V and 3.8 under a voltage condition of 1.50 V. Furthermore, when voltage is used as a variable, results can be obtained that the amount of reducing agent used / syringe pump flow rate needs to satisfy -36 × voltage + 57.8 under a voltage condition of 1.5 V and -36 × voltage + (57.8 ± 1) under a voltage condition of 1.55 V. As such, the amount of reducing agent used can be determined according to the target oxidation number value, and the flow rate and voltage need to be adjusted to sufficiently react the reducing agent.

[0137] Although the embodiments of this specification have been described in more detail with reference to the attached drawings, this specification is not necessarily limited to these embodiments and may be modified in various ways within the scope of the technical spirit of this specification. Accordingly, the embodiments disclosed in this specification are intended to explain, not limit, the technical spirit of this specification, and the scope of the technical spirit of this specification is not limited by these embodiments. Therefore, the embodiments described above should be understood as illustrative in all respects and not restrictive. The scope of protection of this specification shall be interpreted by the claims, and all technical spirits within an equivalent scope shall be interpreted as being included within the scope of rights of this specification.

Claims

1. Liquid electrode storage unit; Electrochemical treatment unit including an anode and a cathode; An anode supply line connecting the liquid electrode storage unit and the inlet of the anode unit, and a cathode supply line connecting the liquid electrode storage unit and the inlet of the cathode unit; An anode recovery line connected to the outlet of the anode section and a cathode recovery line connected to the outlet of the cathode section; and A vanadium ion-containing liquid electrode manufacturing apparatus comprising a reducing agent supply unit that stores a liquid reducing agent and directly supplies the liquid reducing agent to the anode through the anode supply line.

2. In Paragraph 1, A vanadium ion-containing liquid electrode manufacturing apparatus in which an electrochemical reduction reaction of the first liquid electrode is performed at the cathode portion of the electrochemical processing unit while impurities contained in the first liquid electrode are removed, and an oxidation reaction of the reducing agent is performed at the anode portion of the electrochemical processing unit.

3. In Paragraph 2, A vanadium ion-containing liquid electrode manufacturing apparatus in which an electrochemical oxidation reaction of the first liquid electrode and a reduction reaction by the reducing agent are performed at the anode portion of the electrochemical processing unit.

4. In Paragraph 2, A vanadium ion-containing liquid electrode manufacturing apparatus in which an electrochemical oxidation reaction of the reducing agent is performed at the anode portion of the electrochemical treatment portion.

5. In Paragraph 1, A vanadium ion-containing liquid electrode manufacturing device in which the anode recovery line and the cathode recovery line are connected to the liquid electrode storage unit.

6. In Paragraph 1, The above-mentioned reducing agent supply unit comprises a syringe pump, a vanadium ion-containing liquid electrode manufacturing apparatus.

7. (a) A step of supplying a first liquid electrode containing a first vanadium ion stored in a liquid electrode storage unit to the anode and cathode of an electrochemical treatment unit, respectively, through an anode supply line and a cathode supply line; (b) supplying a liquid reducing agent to the anode supply line from a reducing agent supply unit connected to the anode supply line, so that the first liquid electrode and the reducing agent are supplied together to the anode; (c) a step in which an electrochemical reduction reaction of the first liquid electrode is performed at the cathode portion of the electrochemical treatment unit, and an oxidation reaction of the reducing agent is performed at the anode portion of the electrochemical treatment unit; (d) a step of mixing the first liquid electrode that passed through the anode and the first liquid electrode that passed through the cathode to form a second liquid electrode containing second vanadium ions; and (e) A method for manufacturing a vanadium ion-containing liquid electrode comprising the step of recovering the second liquid electrode.

8. In Paragraph 7, A method for manufacturing a vanadium ion-containing liquid electrode, wherein the reducing agent comprises one or more of formic acid, formaldehyde, methanol, ethanol, oxalic acid, and ammonium hydroxide.

9. In Paragraph 7, A method for manufacturing a vanadium ion-containing liquid electrode, wherein an electrochemical oxidation reaction of the first liquid electrode and a reduction reaction by the reducing agent are performed at the anode portion of the electrochemical treatment portion.

10. In Paragraph 7, A method for manufacturing a vanadium ion-containing liquid electrode, wherein an electrochemical oxidation reaction of the reducing agent is performed at the anode portion of the electrochemical treatment portion.

11. In Paragraph 7, In step (c) above, A method for manufacturing a vanadium ion-containing liquid electrode, wherein the average oxidation number of vanadium ions of the first liquid electrode is lowered as it passes through the cathode portion, and the average oxidation number of vanadium ions of the first liquid electrode is maintained or increased to less than 1 as it passes through the anode portion.

12. In Paragraph 7, In step (a) above, the vanadium ions of the first liquid electrode have an average oxidation state of 4 to 5, and A method for manufacturing a vanadium ion-containing liquid electrode, wherein in step (d) above, the vanadium ions of the second liquid electrode have a lower average oxidation number than the vanadium ions of the first liquid electrode.

13. In Paragraph 12, A method for manufacturing a vanadium ion-containing liquid electrode, wherein the average oxidation number of the second liquid electrode is 3.0 to 3.

7.

14. In Paragraph 12, The first liquid electrode that passed through the above cathode part contains trivalent vanadium ions (V 3+ ) including, and the first liquid electrode that has passed through the anode part contains tetravalent vanadium ions (V 4+ Includes ) or, The first liquid electrode that passed through the above cathode part contains divalent vanadium ions (V 2+ ) including, and the first liquid electrode that has passed through the anode part contains pentavalent vanadium ions (V 5+ A method for manufacturing a vanadium ion-containing liquid electrode comprising ).

15. In Paragraph 7, A method for manufacturing a vanadium ion-containing liquid electrode, wherein, in step (c) above, impurities contained in the first liquid electrode are removed from the cathode portion.

16. In Paragraph 7, A method for manufacturing a vanadium ion-containing liquid electrode, wherein the amount (L) of the above reducing agent is determined within a 10% error range of the value determined by the following Equation 1 according to the target oxidation number value. [Equation 1] Target oxidation number value = X - (c*d*e) / (a*b) (In Equation 1, X is the oxidation number of the first liquid electrode, a is the molar concentration of vanadium ions (M), b is the amount of liquid electrode (L), c is the molar concentration of the reducing agent (M), d is the amount of reducing agent used (L), and e is the number of electron donors of the reducing agent)

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