KR20120044489A - Electro-conductive adhesive for cdi electrode and preparation of electrode using the same - Google Patents

Abstract

The present invention relates to a conductive adhesive for an electrode used in a CDI (Capacitive Deionization) process apparatus and to manufacturing an electrode using the same, wherein the conductive adhesive is kneaded with carbon black as a conductive material in a solution in which chitosan, an organic acid and a derivative thereof are dissolved in a dispersion medium. It is characterized by one. The conductive adhesive is inserted into the bonding surface between the current collector and the electrode material to reduce lifting and voids between the interfaces and to improve the adhesion between the interfaces than conventional electrodes. As a result, peeling of the electrode material from the current collector can be prevented and the life of the electrode can be maintained for a long time. In addition, the capacitance of the electrode is increased by reducing the electrode resistance of the electrode itself.

Description

Electro-conductive adhesive for CDI electrode and preparation of electrode using the same}

The present invention relates to a conductive adhesive for an electrode used in a CDI (Capacitive Deionization) processing apparatus and an electrode manufacturing using the same.

Capacitive deionization (hereinafter referred to as CDI) process equipment applies a voltage between two electrodes to electrochemically adsorb ions in solution on the surface of the electrode (anion on the anode and cation on the cathode). Refers to a device that removes dissolved ions. When the adsorption of ions on the CDI electrode is saturated, the polarity of the electrode is reversed to facilitate the desorption of the adsorption ion, thereby simplifying the regeneration of the electrode. This electrical purification method does not use chemicals such as acid ionic base such as ion exchange resin method or reverse osmosis method for electrode regeneration, so less waste water is generated and the device is simple and highly integrated. Since it is operated under the conditions, it is more economical in terms of energy efficiency than other treatment methods. For this reason, it is used in many places in the wastewater treatment process and is emerging as an effective water purification method in desalination and water treatment.

As the active material of the CDI electrode, activated carbon, carbon aerogel, carbon nanotube, and the like are commonly used. Although carbon aerogels and carbon nanotubes have a large surface area and a large number of micropores, they are easy to adsorb and desorption of ions and thus have excellent performance as CDI electrode materials, but they are expensive to manufacture and are applied to dispersion processes and electrodes that slurry them. There has been a disadvantage that the coating process is difficult. Therefore, activated carbon, which is easy to slurry and apply electrode active materials, is mainly used.

On the other hand, when activated carbon is used as an electrode active material, voids are formed in the joint surface between the carbon sheet, which is the current collector, and the activated carbon, which is an electrode material, thereby increasing the electrode resistance, and the adhesion of the electrode material is decreased, thereby increasing the charge / discharge cycle of the CDI electrode. There was a problem in that activated carbon, which is an electrode material, fell and caused performance deterioration.

In order to solve the above problems, the present invention eliminates interfacial lifting and voids between the carbon sheet as the current collector and the polarized porous activated carbon as the electrode material, thereby increasing the adhesion between the interfaces, thereby preventing the peeling of the electrode material from the current collector. SUMMARY OF THE INVENTION An object of the present invention is to provide a conductive adhesive for capacitive deionization (CDI) electrodes that can maintain the life of an electrode for a long time and increase the capacitance by reducing the electrode resistance of the electrode itself.

In order to achieve the above object,

The present invention is 70 ~ 85wt% dispersion medium of deionized water,

5-10 wt% of water-soluble chitosan,

5 to 10 wt% of a crosslinking agent of an organic acid or a derivative thereof,

A conductive adhesive for CDI electrodes composed of a mixture of carbon black conductive material 2-15 wt%,

It relates to an electrode manufacturing method using the conductive adhesive for CDI electrode,

Preparing a conductive adhesive by adding 5-10 wt% of a water-soluble chitosan, 5-10 wt% of a crosslinking agent of an organic acid or a derivative thereof, and 2-15 wt% of a conductive material of carbon black to 70-85 wt% of a dispersion medium of deionized water;

Applying the conductive adhesive to the surface of the carbon sheet on the conductive adhesive, and heating and drying to form a conductive adhesive layer having a dry thickness of 0.2 to 50;

Coating and drying the activated carbon slurry as an electrode material;

An electrode manufacturing method using a conductive adhesive for CDI electrodes consisting of a pressing step to improve the homogeneity of the electrode is a main technical configuration.

And, the water-soluble chitosan is characterized in that the deacetization degree is chitosan with 40 to 60%.

The organic acid is characterized in that any one or a mixture of two or more selected from the polybasic acid of citric acid, maleic acid, succinic anhydride, pyromellitic acid or trimellitic acid.

Hereinafter, the technical configuration will be described in detail.

The present invention relates to a conductive adhesive for an electrode used in a CDI (Capacitive Deionization) process apparatus and to manufacturing an electrode using the same, wherein the conductive adhesive is composed of a mixture of a dispersion medium, a binder, a crosslinking agent, and a conductive agent.

The dispersion medium is mainly determined by the use of the conductive adhesive. In the present invention, since the conductive adhesive is used for water treatment of the water softener, deionized water is used.

Deionized water is mainly used, but in combination with an alcohol solvent such as methanol, ethanol or isopyrophyll alcohol, if necessary, for the purpose of lowering the surface tension for improving the leveling property at the time of applying the conductive adhesive. You may.

The dispersion medium is used within the range of 70 to 85wt% with respect to the total content of the conductive adhesive, when the amount of use is less than 70wt%, there is a problem that the coating film formation, that is, the viscosity is difficult to increase due to the increase in coating properties of the conductive adhesive, exceeding 85wt% Even if the viscosity is too low, the coating film is difficult to form, while the adhesive performance of the conductive adhesive is problematic, it is preferable to use the dispersion medium within the range of 70 to 85wt% based on the total content of the conductive adhesive.

The water-soluble chitosan is characterized in that the deacetization degree is chitosan 40 ~ 60%, molecular weight 30,000 ~ 60,000. Basically, chitosan has an insoluble property that is insoluble in water or alkali, but is not used in industrial use because it is dissolved in weak acid such as lactic acid, citric acid and acetic acid. As a method of water-soluble chito oxidation, there is a method of lowering the first molecular weight to oligosaccharide, a method of polymerizing a functional group to a second chitosan to make a water-soluble derivative, and a method of setting a third degree of deacetization to 40 to 60%. When the water-soluble chitosan of the first method is used, the fluidity and binding properties required for the performance of the conductive adhesive do not appear, and when the water-soluble chitosan of the second method is used, the chitosan itself is expensive, which is not economical. However, chitosan treated with 40 to 60% deacetization is soluble in water without lowering its molecular weight and is excellent in its industrial use. In addition, the water-soluble chitosan has affinity with carbon black due to the presence of amine (-NH2) in the functional group, and thus it is possible to satisfactorily disperse the carbon black particles in the slurry.

On the other hand, the amount of water-soluble chitosan used as a binder component of the binder is determined within the range of 5 to 10wt% with respect to the total content of the conductive adhesive, when the amount is less than 5wt%, it is difficult to obtain a stable binder layer, If the content exceeds 10wt%, the coating property is poor or the cost is uneconomical. Therefore, the amount of the binder is 5 to 10wt% based on the total content of the conductive adhesive in view of the binding property and the cost. It is preferable to use within the range of%.

In addition, with respect to the binder, the organic acid and its derivatives are used as a binder of the carbon sheet as the current collector and the activated carbon layer as the electrode material to form a conductive layer, and then act as a crosslinking agent of the water-soluble chitosan during heat drying. The crosslinked water-soluble chitosan has a function of preventing peeling of the electrode material by providing excellent adhesion between the current collector and the electrode material.

The organic acid of the crosslinking agent may be selected from oxalic acid, malonic acid, malic acid, tartaric acid, methalic acid, citric acid, adipic acid, maleic acid, pyromellitic acid, phthalic acid, trimellitic acid and succinic acid in any one or two or more mixtures thereof. The organic acid derivative of the crosslinking agent is selected from acid anhydrides of the polybasic acids, salts of some or all of the carboxyl groups of polybasic acids, in particular ammonium salts or amine salts. In particular, it is preferable to select and use from pyromellitic acid, trimellitic acid, or acid arsenic matter which are trivalent or more aromatic polycarboxylic acid from a crosslinking | crosslinking point.

In addition, the amount of the organic acid or its derivative added as a crosslinking agent component of the binder is used within the range of 5 to 10wt% with respect to the total content of the conductive adhesive. Low, there is a problem in that the binding layer formed to reduce the adhesiveness between the current collector and the electrode material, if the content exceeds 10wt% crosslinkability is poor and the adhesiveness is also inhibited, the crosslinking agent is the total amount of the conductive adhesive It is preferable to use within the range of 5 to 10wt%.

Carbon black, which is the conductive agent, has a structure in which carbon atoms having an average primary particle diameter of 10 to 200 nm, preferably 20 to 100 nm, are secondarily aggregated in a chain shape and have such a secondary particle structure. Carbon black is excellent in conductivity as a conductive agent.

The carbon black may be any one or a mixture of two or more selected from acetylene black, Ketjen black, Super P black, and VGCF (vaper gas cabon fiber), but is not particularly limited thereto.

The amount of the conductive agent is determined within the range of 2 to 15wt% with respect to the total content of the conductive adhesive, and when the amount is less than 2wt%, a problem arises that the conductive ability cannot be expressed, and when the amount exceeds 15wt% Since most of the dispersion medium is absorbed by the carbon black, the fluidity is remarkably lost and handling is difficult. Therefore, the amount of the conductive agent is maintained within the range of 2 to 15 wt% based on the total content of the conductive adhesive. Preferably it is maintained in the range of 2 to 10wt%.

Next, looking at the manufacturing of the conductive adhesive used in the present invention, first dissolving by adding 5-10 wt% of water-soluble chitosan as a binder to 70 ~ 85wt% of the dispersion medium of deionized water,

5-10 wt% of an organic acid or a derivative thereof, which is a crosslinking agent of water-soluble chitosan, is added,

As a final process, the conductive adhesive of the present invention is added by kneading and dispersing using a high speed impeller disperser, homogenizer, ball mill, sand mill or planetary mixer, paste mixer by adding 2-15 wt% of carbon black conductive agent. To prepare.

Looking at the electrode manufacturing method using the conductive adhesive prepared through the above process, the conductive adhesive is applied to the surface of the carbon sheet on the surface of the carbon sheet that is the current collector for the CDI electrode with a drying thickness of 0.2 to 50, and heat-drying the applied conductive adhesive Forming a conductive adhesive layer through the process;

Coating and drying the activated carbon slurry as an electrode material;

This is done through a pressing step to improve the homogeneity of the electrode.

In the method for forming the conductive adhesive layer, the conductive adhesive is applied to a carbon sheet surface, which is a current collector for CDI electrodes, by a coating method with a thickness of 0.2 to 50, preferably 1.0 to 20, by drying, followed by heat drying to form a conductive adhesive layer. By forming

The coating method may be any one selected from gravure coat, gravure reverse coat, slide dye coating, comma direct coating, comma reverse coating, and die nozzle coating. The species method is used.

In the heat drying, heat drying at 110 to 5 to 10 minutes in order to sufficiently form crosslinking of the water-soluble chitosan, and heat drying at 150 to 5 to 10 minutes is preferable.

The reason for heating and drying in two stages by changing the drying temperature is to form sufficient crosslinking density of the crosslinking agent to increase the adhesion of the conductive adhesive to the current collector and to remove the residual dispersion medium present in the conductive adhesive layer.

If the cross-linking agent component of the conductive adhesive is less than 5 minutes at 110, there is a problem in that the cross-linking component of the conductive adhesive is not sufficiently crosslinked and lacks adhesion with the current collector. There is. In addition, if it is less than 5 minutes at 150, the remaining dispersion medium present in the conductive adhesive layer is not removed, and thus the adhesiveness with the electrode material is inferior. If it is more than 10 minutes, the cost of electrode production is economical. There is a problem.

The activated carbon slurry as the electrode material is formed of activated carbon as a polarizable porous active material and a PTFE binder as a binder.

More specifically, the activated carbon slurry is prepared by rolling an alcohol to a mixture of 96 wt% activated carbon having a size of 10 and 4 wt% of a PTFE solution (solid content 60%) as a binder and rolling it to a predetermined thickness by a roll press. .

As a press method in the pressing step, a method selected from a cold press or a hot press is used.

As described above, the conductive adhesive for the electrode used in the CDI (Capacitive Deionization) process apparatus according to the present invention and the electrode prepared by using the same, the bonding surface between the collector carbon sheet and the electrode material polarized porous activated carbon It is inserted to reduce the lifting and voids between the interface than the conventional electrode and to increase the adhesion between the interface. As a result, peeling of the electrode material from the current collector can be prevented and the life of the electrode can be maintained for a long time. In addition, the capacitance of the electrode is increased by reducing the electrode resistance of the electrode itself.

Hereinafter, the specific contents according to the technical configuration will be described through embodiments.

First, a conductive adhesive for a CDI electrode and an electrode manufacturing method using the same according to a preferred embodiment of the present invention will be described in detail, but the present invention is not limited or limited by the following examples.

Example 1 Preparation of an Electrode Using a Conductive Adhesive

Preparation of Conductive Adhesive

The conductive adhesive of Example 1 was prepared by adding 800 g of deionized water to a paste mixer, dissolving 50 g of water-soluble chitosan and 50 g of citric acid as a binder, and then adding 100 g of Super P black as a conductive material.

Preparation of the electrode

Next, the activated carbon electrode which is an electrode material was manufactured by the following method. 960 g of activated carbon having an average size of 10 and 40 g of a PTFE solution (60% solids) as a binder were stirred with a paste mixer, and alcohol was added to form a roll press until a constant thickness was obtained to obtain an electrode.

 Formation of conductive adhesive layer on current collector and integration of electrodes

The formation of the conductive adhesive layer on the current collector and the integration of the electrodes are first performed by applying the above-mentioned conductive adhesive on the surface of the carbon sheet, which is a current collector for CDI electrodes, using a comma direct coater, and then binding the electrodes thereon, followed by a dry zone. At 110 to 5 minutes and 150 to 5 minutes were heat-dried to form the conductive adhesive layer 1 and the electrode layer 200.

The press was applied again to maintain the uniformity of the integrated electrodes obtained above.

Coating film peeling test of electrode

After drying the electrode prepared in Example 1 at 90 for 24 hours, attaching a pressure-sensitive adhesive tape (3M Scotch Mending Tape) on the electrode surface and then reciprocating 1 weight rubber roller for 1 week to compress the film and the adhesive tape Let's do it. The case where the crimped adhesive tape was peeled off at a constant speed and the film peeled from the carbon sheet which is the current collector was not peeled was determined as.

Electrical resistance measurement test of electrode

The electrical resistance measurement of the electrode manufactured in Example 1 was carried out by placing the electrode punched at 13 mm as a resistance value in the thickness direction of the electrode on a silver plate, and placing a 11 mm silver bar on the coating film surface under a load of 500 gf. The resistance value between silver bars was measured.

Example  2 to 5: Preparation of Electrode Using Conductive Adhesive

A coating film peeling test and an electrical resistance of the electrode were measured (Test Examples 3 to 6) in the same manner as in Example 1, except that the conductive adhesive was prepared by the formulation of Table 1 below, and the results are shown in Table 2.

Comparative example  1 to 3

Comparative Examples 1 to 2 were prepared in the same manner as in Example 1 except that the conductive adhesive was prepared in the formulation of Table 1, and the coating film peeling test and the electrical resistance of the electrode were measured, and the results are shown in Table 2.

In Comparative Example 3, an electrode was prepared without a conductive adhesive, and the coating film peeling test and the electrical resistance of the electrode were measured, and the results are shown in Table 2.

Conductive Adhesive Binder Conductive material Dispersion Water soluble chitosan Organic acids Super P Black Deionized water Example 1 70g 70 g citric acid 100 g 760 g Example 2 50 g 50 g maleic acid 100 g 800 g Example 3 60 g Succinic anhydride 60g 100 g 780 g Example 4 100 g 50 g of pyromellitic acid 100 g 750 g Example 5 50 g 50 g of pyromellitic acid 100 g 800 g Comparative Example 1 100 g - 100 g 800 g Comparative Example 2 CMC 100g - 100 g 800 g Comparative Example 3 - - - -   Total amount is based on 1000g

Electrode coating film peel test and electric resistance measurement result Coating film peeling test of electrode Electrical resistance of electrode Example 1 ○ ◎ Example 2 ○ ◎ Example 3 ○ ◎ Example 4 ○ ◎ Example 5 ○ ◎ Comparative Example 1 × ○ Comparative Example 2 × × Comparative Example 3 × ×

(Film peeling test of electrode: The case where a film peeled from the carbon sheet which is an electrical power collector is x, and the case where it is not peeled is set as (circle).

 Electrical resistance of the electrode: ◎ is less than 20% or less than Comparative Example 3, ○ is less than or less than 10% and less than 20%, and x is less than or equal to Comparative Example 3 Sometimes.)

As can be seen from the results of Table 2, when the electrode coated with the conductive adhesive according to the present invention is used, it is possible to obtain an electrode which can prevent the peeling of the electrode material and reduce the electrical resistance.

Claims (4)

70-85 wt% of dispersion medium of deionized water,
5-10 wt% binder of water-soluble chitosan,
5 to 10 wt% of a crosslinking agent of an organic acid or a derivative thereof,
A conductive adhesive for CDI electrodes, characterized in that the composition is composed of a mixture of carbon black conductive material 2 ~ 15wt%.
The method according to claim 1,
The water-soluble chitosan has a deacetization degree of 40 to 60% and a molecular weight of 30,000 to 60,000 conductive adhesive for CDI electrodes. Preparing a conductive adhesive by adding 70 to 85 wt% of a deionized water dispersion medium to 5 to 10 wt% of a water-soluble chitosan binder, 5 to 10 wt% of a crosslinking agent of an organic acid or a derivative thereof, and 2 to 15 wt% of a conductive material of carbon black. Wow,
Applying the conductive adhesive to the surface of the carbon sheet, binding the electrode material thereon, and heating and drying to form a conductive adhesive layer having a dry thickness of 0.2 to 50 to form an integration with the electrode material;
Electrode manufacturing method using a conductive adhesive for CDI electrode, characterized in that consisting of a pressing step to improve the homogeneity of the electrode. The method according to claim 3,
The electrode material is a CDI electrode characterized in that a mixture of 960 g of activated carbon having a size of 10 and 40 g of a PTFE solution (60% solids) as a binder is mixed with alcohol, stirred and mixed with a paste mixer, and then rolled to a predetermined thickness with a roll press. Electrode manufacturing method using a conductive adhesive for use.