KR102356077B1 - Capacitive deionization module with a series lamination structure possible for minimizes electrode reactions and enables stable operation - Google Patents

Abstract

The present invention improves the contact resistance between the electrode connected directly to the connection terminal of the power supply unit and the inner electrode where induced charging is formed and the outermost electrode where direct charging is formed in implementing a series stacking structure of electrodes using the charging principle It relates to a capacitive desalination module of a series-stacked structure that enables stable operation while minimizing electrode reaction by limiting the amount of supply current according to the predefined maximum allowable charge (MAC) along with the design of separation of the capacitance of the an electrode unit in which electrodes are stacked to form a gap; and a power supply unit for supplying a positive potential and a negative potential to a pair of outermost electrodes among the electrodes constituting the electrode unit, respectively, so that the inner electrodes positioned between the pair of outermost electrodes are supplied with a potential through indirect charging through induction charging; Including, wherein the electrode is coated with activated carbon powder on a conductive graphite current collector, while the activated carbon powder coating layer of the outermost electrode is 1.5 to 2.0 times thicker than the activated carbon powder coating layer of the inner electrode, the area of the outermost electrode is the It is characterized in that it is formed to be smaller than the area of the inner electrode by 10% or less.

Description

Capacitive deionization module with a series lamination structure possible for minimizes electrode reactions and enables stable operation

The present invention relates to a capacitive desalination module having a series stacked structure, and more particularly, in implementing a series stacked structure of electrodes using the charging principle, the contact resistance between the connection terminal of the power supply and the electrode directly connected thereto is improved, Series stacking that enables stable operation while minimizing electrode reaction by limiting the amount of supply current according to the predefined maximum allowable charge (MAC) along with the design of separating the capacitance of the inner electrode where induced charging is formed and the outermost electrode where direct charging is formed It relates to a capacitive desalination module of the structure.

In general, capacitive deionization (CDI) technology is a technology that forms an electric double layer (EDL) at the interface of a porous carbon electrode material and absorbs and removes ionic substances dissolved in water. .

That is, the capacitive desalination technology is a fluid containing ionic substances in a unit cell composed of a pair of porous carbon electrodes with a high specific surface area, a selective ion exchange membrane, and a mesh spacer through which the fluid can move. Electrostatic attraction between the positive and negative ions contained in the fluid flowing through the spacer to the surface of the electrode charged with opposite charges It is moved to form an electric double layer on the electrode surface and is adsorbed.

On the other hand, if the porous carbon electrode fills all the capacitance and no more adsorption occurs, the supply of the potential applied to the carbon electrode is stopped or short, or the potential supplied during the adsorption process is reversed (Reverse Charging). ), the ions adsorbed on the surface of the carbon electrode are desorbed, and the process of regeneration of the electrode is repeated.

This capacitive desalination technology is divided into a parallel structure method (A) and a series structure method (B), respectively, shown in FIGS. In the case of the structural method (A), there is a structurally complicated disadvantage because the contact terminals must be installed on both the positive and negative electrodes constituting the module.

And in the case of the series structure method (b), the total amount of the potential to be supplied to the unit cells constituting the module is supplied only to the electrodes at both ends of each of a plurality of positive and negative electrodes constituting the module, and to the induction charging electrode located inside the module. There is an advantage in that the structure is very simple because there is no contact terminal part of the inner induction charging part constituting the module on the principle that the supplied potential is divided. Since a very high potential is temporarily applied to the electrode part, a somewhat higher electrode potential is formed compared to the internally induced charging electrode part, so there is a disadvantage in that the voltage distribution and imbalance appear as a whole.

The module of the series structure method (B) has a higher potential than the internal inductively charged electrode cell electrode in the outermost unit cell electrode and terminal portion that is in direct contact with the external power supply due to the voltage distribution characteristic described above. As compared to the internal inductively charged electrode cell, the contact terminal electrode cell quickly reaches the limit capacitance of the unit electrode cell, thereby causing various types of electrode reactions that should be avoided in capacitive deionization. .

In particular, when the external contact terminal of the outermost electrode cell comes into contact with the saline solution inside the module, there is a very high risk that the electrode reaction of the charging electrode part of the contact terminal at both ends is induced, which shortens the life of the module and electrode and reduces the efficiency. do. In addition, when graphite, which is mainly used as a current collector coated with an activated carbon electrode, as in the module of the existing parallel structure method (A), is used as a terminal, a part of the graphite current collector is oxidatively damaged due to instantaneous high potential formation There is also a problem in that the contact portion of the graphite current collector with weak physical strength may be damaged.

In addition, when copper (Cu: copper) or general metal material with low electrical resistance is applied as the electrode contact terminal, it is formed by contact with the solution inside the module or oxidation reaction caused by _{internal moisture and oxygen (O 2 ) components in the air.} There is a problem in that the metal oxide layer rather increases the electrical resistance and consequently reduces the desalination efficiency.

Republic of Korea Patent Registration No. 10-1741529

Accordingly, an object of the present invention is to improve the contact resistance between the electrode connected directly to the connection terminal of the power supply unit and to improve the contact resistance between the electrode directly connected to the connection terminal of the power supply and the inner electrode where the induced charging is formed in realizing the series stacked structure of the electrodes using the charging principle. The purpose of this is to provide a capacitive desalination module with a series stack structure that can minimize electrode reaction and allow stable operation by limiting the amount of supply current according to the predefined maximum allowable charge (MAC) along with the design of separating the capacitance of the outermost electrode.

As a means to solve the above problems, the capacitive desalination module (hereinafter referred to as the 'module of the present invention') having a series stack structure capable of minimizing electrode reaction and stable operation of the present invention, a plurality of electrodes form a mutual gap and stacked electrode units; and a power supply unit for supplying a positive potential and a negative potential to a pair of outermost electrodes among the electrodes constituting the electrode unit, respectively, so that the inner electrodes positioned between the pair of outermost electrodes are supplied with a potential through indirect charging through induction charging; Including, wherein the electrode is coated with activated carbon powder on a conductive graphite current collector, while the activated carbon powder coating layer of the outermost electrode is 1.5 to 2.0 times thicker than the activated carbon powder coating layer of the inner electrode, the area of the outermost electrode is the It is characterized in that it is formed so as to be smaller than 90% to less than 100% of the area of the inner electrode.

As an example, the power supply unit is connected to the pair of outermost electrodes and includes a pair of connection terminals for supplying a positive potential and a negative potential, respectively, and the connection terminal is titanium (Ti) or titanium. It is characterized by being composed of an insoluble material (DSA: Dimension Stable Anode) coated with a metal oxide containing iridium (IrO ₂ ) or ruthenium (RuO _{2 ).}

As an example, the pair of connection terminals and the pair of outermost electrodes are characterized in that they are bonded to each other by a conductive paste adhesive containing carbon black or a conductive polymer binder.

As an example, the power supply unit defines the amount of charge charged with respect to the electrode of the electrode unit until the start of the electrode reaction as a maximum allowable charge (MAC), and is less than or equal to the defined maximum allowable charge (MAC) It is characterized in that it includes a control unit for supplying by limiting the amount of current so that the current is supplied to the electrode.

As described above, in the module of the present invention, the connection terminal of the power supply part is made of an insoluble material in implementing a series stacked structure of electrodes using the charging principle, and the connection between the outermost terminals of the electrode part is made by a conductive paste adhesive. The increase in contact resistance due to physical connection and consequent decrease in current efficiency and damage to the activated carbon electrode are prevented. can have an effect.

In addition, by forming the activated carbon coating layer of the outermost electrode relatively thick compared to the inner electrode to increase the amount of storage, the electrode reaction generated from the excess of the storage capacity due to the high potential instantaneously applied to the outermost terminal directly connected to the connection terminal is prevented. It has the effect of reducing and preventing damage to other materials.

In addition, by limiting the amount of current so that the current is supplied to the electrode below the predefined maximum allowable charge (MAC), there is an effect that the module can be operated stably without electrode reaction.

1A and 1B are diagrams showing a parallel structure method and a series structure method of a conventional capacitive desalination module, respectively.
2 is a view showing a contact structure between a connection terminal and an outermost terminal according to an embodiment of the present invention.
Figure 3 is a view comparing the activated carbon powder coating layer between the outermost terminal and the inner terminal according to an embodiment of the present invention.

Hereinafter, the configuration and operation of the present invention will be described in more detail based on the accompanying drawings. In describing the present invention, the terms or words used in the present specification and claims are based on the principle that the inventor can appropriately define the concept of the term in order to best describe his or her invention. It should be interpreted as meaning and concept consistent with the technical idea of

The module of the present invention includes an electrode part 10 in which a plurality of electrodes are stacked to form a mutual gap 100, 110 and a pair of outermost electrodes among the electrodes 100 and 110 constituting the electrode part 10 ( 100) by supplying a positive potential and a negative potential to the inner electrodes 110 positioned between the pair of outermost electrodes 100, respectively.

That is, the module of the present invention performs a desalting process of desorption of ions using the charging principle according to the stacked structure of the electrode part 10 and the serial power supply method of the plurality of power supplies 20 .

The present invention induces an electrode reaction of the outermost electrode 100 directly connected to the power supply unit as well as a voltage distribution imbalance that may occur due to the characteristics of a series structure power supply method and a consequent deterioration in durability through the embodiments to be described below. so that the problem can be improved.

First, in the module according to an embodiment of the present invention, a pair of outermost electrodes 100 receiving power from the power supply unit 20 and an internal electrode 110 between the pair of outermost electrodes 100 are provided. The activated carbon coating layer of the outermost electrode 100 is formed to be relatively thick so as to prevent electrode reaction and material damage caused by the rapid reaching of the limit capacitance of the outermost electrode 100 caused by the potential difference imbalance.

That is, unlike the internal electrode 110, by increasing the activated carbon coating of the outermost electrode 100 and using it as an electrode with an increased power storage amount of the unit electrode, it is in direct contact with the connection terminal 200 of the power supply unit 20 This is to reduce the excess of the capacitance due to the high potential instantaneously applied to the outermost electrode 100 and the electrode reaction resulting therefrom.

Here, in the present invention, the electrodes 100 and 110 may be a conductive graphite current collector 120 coated with activated carbon powder 130 as shown in FIG. 3 , and in this case, the activated carbon of the outermost electrode 100 . It is preferable that the powder coating layer be formed to be 1.5 to 2.0 times thicker than the activated carbon powder coating layer of the inner electrode 110 .

For example, when the thickness (b) of the graphite current collector 120 is about 250 um, the thickness (a, a1) of the activated carbon powder 130 positioned on both sides of the graphite current collector (b) is coated with about 200 to 250 um. Thus, the inner electrode 110 for induction charging is manufactured, and the outermost electrode 100 used for direct charging differs from the internal electrode 110 with only the cross section of the activated carbon powder 130 having a thickness of about 500 μm (a2). By coating to increase the storage capacity by two times, the electrode reaction due to the excess of the storage capacity can be minimized.

In addition, the total area c2 of the outermost electrode 100 is preferably formed to be smaller than 90% to less than 100% of the area c1 of the inner electrode 110 as shown in FIG. 3 . , which is due to the high potential applied to the outermost electrode 100 that is in direct contact with the connection terminal 200 of the power supply unit 20, a relatively large elliptical electric field is formed compared to the internal induced charging electrode, so the outermost electrode ( This is to minimize the effect of electric field interference of adjacent inductively charged electrodes due to the electric field formed in 100) while minimizing the imbalance in potential transfer between the internal electrodes 110 where inductive charging is made.

Meanwhile, the power supply unit 20 is connected to the pair of outermost electrodes 100 and includes a pair of connection terminals 200 for supplying a positive potential and a negative potential, respectively.

In the case of the connection terminal 200, it is preferable to have a material that does not cause oxidation and corrosion reaction even if there is a partial contact with water or oxygen in the atmosphere.

For example, the connection terminal 200 is made of an insoluble material (DSA: Dimension Stable Anode) coated with a metal oxide 201 containing _{titanium (Ti) or iridium (IrO 2} ) or ruthenium (RuO _{2 ).} By doing so, it is possible to have high dimensional stability and not to dissolve chemically or electrochemically.

In addition, in order to minimize contact resistance between the outermost terminal 100 directly connected to the connecting terminal 200, the graphite current collector 120 of the outermost terminal 100 and the connecting terminal 200 are combined with a conductive binder. The connected connection method is applied.

Referring to FIG. 2 , the pair of connection terminals 200 and the pair of outermost electrodes 100 are interconnected by a conductive paste adhesive 202 containing carbon black or a conductive polymer binder.

At this time, in the case of the connection terminal 200 , it is not connected to the outermost electrode 100 by completely penetrating the casing 30 configured to surround the electrode part 10 , but as shown in FIG. 2 , the casing 30 ) forms a groove in communication with the insertion passage in a portion facing the outermost electrode 100 while providing an insertion passage through which the connection terminal 200 can be inserted, and the conductive paste adhesive 202 is filled in the groove By doing so, the connection terminal 200 is prevented from being directly exposed to the inside of the casing 30 .

As such, when the module of the present invention physically contacts the metal connection terminal 200 to the outermost electrode 100 and uses it, current efficiency decreases due to an increase in physical contact resistance and damage to the activated carbon material electrode due to continuous resistance In order to solve problems such as induced, the connection terminal 200 is made of an insoluble material terminal and a conductive paste adhesive is used between the outermost electrode 100 to reduce the grounding resistance, as well as to the connection terminal 200 and It is possible to increase the compactness and dimensional stability between the outermost terminals 100 .

On the other hand, the power supply unit 20 according to an embodiment of the present invention defines the amount of charge charged to the electrode of the electrode unit until the start of the electrode reaction as a maximum allowable charge (MAC), and the defined maximum allowable charge. It is characterized in that it includes a control unit for supplying by limiting the amount of current so that the current is supplied to the electrode less than the amount of charge (MAC).

In general, in capacitive desalination technology, the electrode potential of the carbon electrode is proportional to the amount of charge supplied to the cell, and it is known that the electrode reaction starts when the electrode potential reaches a certain level. It is said

In a capacitive carbon electrode cell, the electrode reaction proceeds when a charge greater than the maximum allowable charge (MAC) is supplied regardless of cell components or operating conditions. Since it can be operated stably, the maximum allowable current according to the influent concentration is divided by the number of unit electrodes constituting the series module so that the current that exceeds the unit electrode’s capacity compared to the influent concentration is not supplied. This is to enable stable operation of the module without electrode reaction by operating the module by applying a current limit so that current is supplied to the outer electrode 100 .

That is, in the control unit of this embodiment, the amount of charge charged until the start of the electrode reaction is defined as the maximum allowable charge amount (MAC), and the cell potential is related by operating the module based on the total charge within the defined maximum allowable charge amount (MAC). This is to ensure that the electrode can be operated stably without any electrode reaction.

Here, the timing at which the electrode reaction of the electrode starts may be variously performed through known techniques.

For example, in order to more reliably determine the timing of the electrode reaction, the point at which the electrode reaction of the electrode starts can be identified through the instantaneous charge efficiency and pH change during the electrode adsorption process, and the amount of charge charged up to this point is set to the maximum allowable charge (MAC). ) can be calculated and defined.

Those skilled in the art from the above description will be able to see that various changes and modifications are possible without departing from the technical spirit of the present invention. Accordingly, the technical scope of the present invention should not be limited to the content described in the detailed description of the specification, but should be defined by the claims.

10: electrode unit 20: power supply unit
30: casing 100: outermost electrode
110: internal electrode 120: graphite current collector
130: activated carbon powder 200: connection terminal

Claims (4)

an electrode part in which a plurality of electrodes are stacked to form a gap; and
A power supply unit for supplying a positive potential and a negative potential to a pair of outermost electrodes among the electrodes constituting the electrode part, respectively, so that the inner electrodes positioned between the pair of outermost electrodes are supplied with an electric potential by indirect charging through induction charging; includes,
The electrode is coated with activated carbon powder on a conductive graphite current collector, while the activated carbon powder coating layer of the outermost electrode is 1.5 to 2.0 times thicker than the activated carbon powder coating layer of the inner electrode, the area of the outermost electrode is the area of the inner electrode Capacitive desalination module of series-stacked structure capable of minimizing electrode reaction and stable operation, characterized in that it is formed as small as 90% or more to less than 100% of the comparison.
The method of claim 1,
The power supply unit,
and a pair of connection terminals connected to the pair of outermost electrodes to respectively supply positive and negative potentials,
The connection terminal is
Minimization of electrode reaction and stable operation characterized in that it is composed of an insoluble material (DSA: Dimension Stable Anode) coated with a metal oxide containing titanium (Ti) or titanium with iridium (IrO ₂ ) or ruthenium (RuO _{2 )} Capacitive desalination module of series stacked structure.
3. The method of claim 2,
The pair of connection terminals and the pair of outermost electrodes are connected to each other by a conductive paste adhesive containing carbon black or a conductive polymer binder. desalination module.
The method of claim 1,
The power supply unit,
The amount of charge charged to the electrode of the electrode part until the start of the electrode reaction is defined as maximum allowable charge (MAC), and the amount of current is limited so that the current is supplied to the electrode below the defined maximum allowable charge (MAC). A capacitive desalination module of a series stack structure capable of minimizing electrode reaction and stable operation, characterized in that it includes a control unit for supplying it.

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