KR20110016979A - Composite electrode and method for manufacturing the same - Google Patents

Abstract

PURPOSE: A composite electrode and a manufacturing method thereof are provided to increase stability at high temperature and capacity of charge and discharge by increasing a specific surface when a capacitor and a secondary battery are manufactured. CONSTITUTION: A composite electrode includes ceramic or metal porous support(102) and a conductive polymer(101). The conductive polymer is formed on the surface of the porous support. One or more carbon nano tubes are vertically formed on the surface of the porous support.

Description

Composite electrode and method for manufacturing the same

The present invention relates to a composite electrode and a method of manufacturing the same.

In general, high-performance portable power supplies are a key component of the finished products essential to all portable information and communication devices, electronic devices, electric vehicles, and the like. All of the next generation energy storage systems that are being developed recently use electrochemical principles, such as lithium (Li) secondary batteries and electrochemical capacitors.

An electrochemical capacitor is an energy storage device that stores and supplies electrical energy by using a capacitor behavior caused by an electrochemical reaction between an electrode and an electrolyte. The electrochemical capacitor has a much higher energy density and output density than conventional electrolytic capacitors and secondary batteries. Recently, it has received much attention as a new concept of energy storage power source capable of storing or supplying energy rapidly. Electrochemical capacitors are expected to be used as a back-up power source for electronic devices, pulse power sources for portable mobile communication devices, and high-power power sources for hybrid electric vehicles due to their ability to supply a large amount of current in a short time.

These electrochemical capacitors are based on the electrical double layer capacitor (EDLC) using the principle of electrical double layer occurring between the electrode and the electrolyte, and adsorption reaction on the electrode surface of the ions in the electrolyte or oxidation / reduction reaction of the electrode. It is classified as a supercapacitor that expresses a supercapacitor with a maximum capacity of about 10 times as large as that of the EDLC type by the pseudocapacitance generated in the faradaicreation accompanied by the transfer of charge between the electrode and the electrolyte. do.

Metal oxides or conductive polymers are mainly used as electrode materials for supercapacitors, and most of them are transition metal oxide materials, and ruthenium oxide is particularly high in aqueous electrolytes. Most research is being carried out due to its capacity, long operating time, high electrical conductivity and excellent high rate characteristics. However, when using such an aqueous electrolyte, there is a disadvantage that the energy density is limited because the operating voltage of the aqueous electrolyte is limited to 1V.

For this reason, electrode materials such as vanadium oxide, manganese oxide, nickel oxide, and cobalt oxide, which can be used in organic electrolytes having an operating voltage of 2.3 V or more, have been actively developed. However, these alternative electrode materials have been applied to ruthenium oxide. It does not show corresponding electrochemical properties.

On the other hand, as part of a method for increasing the electrochemical characteristics of the current metal oxide electrode, a study to configure a carbon material / metal oxide composite electrode by combining a metal oxide electrode material with a large specific capacitance and a carbon-based material having excellent electrical conductivity Is on a global trend.

Reported to date, a method for manufacturing a composite electrode of a carbon-based material and a metal oxide includes a carbon material / metal oxide prepared by mixing a carbon-based material in the synthesis of a metal oxide in a paste form by mixing a conductive material and a binder. Alternatively, there is a pasting method in which a metal oxide, a conductive material, and a binder, which are already synthesized, are mixed with a carbon material to form a paste, and then applied to a current collector.

However, when the carbon material / metal oxide composite electrode is manufactured by such a pasting method, the process is very complicated and takes a long time, a multi-step process, and the use of a conductive material and a binder is indispensable, but they do not have the specific capacitance of the electrode. These are pointed out as problems that do not participate in the actual electrochemical reactions that they express.

The present inventors have led to the present invention as a result of studying the support of the electrode having a larger specific surface area and not a carbon material.

Accordingly, an object of the present invention is to provide a composite electrode having a large specific surface area and high temperature stability.

In one aspect of the invention, a ceramic or metal porous support; And a conductive polymer or metal oxide formed on the surface of the ceramic porous support.

In another aspect of the invention, a ceramic or metal porous support; At least one carbon nanotube formed perpendicular to the surface of the ceramic porous support; And a conductive polymer or metal oxide formed on the surface of the ceramic porous support on which the carbon nanotubes are formed.

In another aspect of the present invention, a ceramic or metal porous support plated with a high conductivity metal component; At least one carbon nanotube formed perpendicular to the surface of the plated porous support; And a conductive polymer or metal oxide formed on the surface of the porous support on which the carbon nanotubes are formed.

When manufacturing a capacitor or a secondary battery using a composite electrode according to a preferred embodiment of the present invention, the specific surface area is increased to increase the charge and discharge capacity and energy density / output density, and the stability and reliability at high temperature Can be.

1 is a cross-sectional view showing a composite electrode according to an embodiment of the present invention.
2 is a cross-sectional view of a composite electrode according to another exemplary embodiment of the present invention.
3 is a cross-sectional view of a composite electrode according to another exemplary embodiment of the present invention.
Figure 4 is an SEM image of a ceramic support made of short fibers that can be used in the present invention.
5 is an SEM photograph of a ceramic support made of long fibers that can be used in the present invention.
6 is a SEM photograph of a ceramic structure made in the form of a foam that can be used in the present invention.
7 is a schematic diagram of a capacitor according to an embodiment of the present invention.
8 is a short fiber ceramic porous support that can be used in the present invention.
9 is an SEM image of a polypyrrole-coated ceramic filter according to an embodiment of the present invention.
10 is a photograph of the reduced magnification of FIG. 9.
FIG. 11 is an enlarged photograph of the ceramic fiber of FIG. 9. FIG.
12 is experimental data of an embodiment of the present invention.

As the invention allows for various changes and numerous embodiments, particular embodiments will be illustrated in the drawings and described in detail in the written description. However, this is not intended to limit the present invention to specific embodiments, it should be understood to include all transformations, equivalents, and substitutes included in the spirit and scope of the present invention. In the following description of the present invention, if it is determined that the detailed description of the related known technology may obscure the gist of the present invention, the detailed description thereof will be omitted.

Terms (a) and (b) may be used to describe various components, but the components should not be limited by the terms. The terms are used only for the purpose of distinguishing one component from another.

The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting of the present invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In this application, the terms "comprise" or "having" are intended to indicate that there is a feature, number, step, operation, component, or a combination thereof described in the specification, but one or more other features or numbers. It is to be understood that the present invention does not exclude in advance the possibility of the presence or the addition of steps, actions, components, or a combination thereof.

Hereinafter, a preferred embodiment of a composite electrode and a method of manufacturing the same according to the present invention will be described in detail with reference to the accompanying drawings, in the description with reference to the accompanying drawings, the same or corresponding components are given the same reference numerals and Duplicate description thereof will be omitted.

1 illustrates a ceramic or metal porous support 102 and a conductive polymer 101 formed on a surface according to an embodiment of the present invention.

The ceramic porous support that can be used in the present invention is not limited in shape as long as it has a surface area that can be used for the electrode, but preferably, ceramic paper using short fibers, ceramic paper using long fibers, ceramic paper or foam using ceramic fine particles It may be in the form of a ceramic structure having an internal structure of the form. For example, Figure 4 shows a ceramic paper made of short fibers, Figure 5 shows a ceramic paper made of long fibers, Figure 6 shows a ceramic structure made in the form of foam.

When the ceramic porous support is used, high temperature stability and reliability can be ensured, so that it can be used in fields requiring high temperature firing, unlike conventional electrodes.

Metallic porous supports can be prepared using commonly known porous thin film manufacturing techniques, Li, Al, Sn, Bi, Si, Sb, Ni, Cu, Ti, V, Cr, Mn, Fe, Co, Zn, Mo , W, Ag, Au, Pt, Ir, Ru and their alloys or oxides can be used.

In the case of the ceramic support, it is advantageous in terms of specific surface area and high temperature stability, but there is a need to form a conductive layer on the surface of the ceramic support in order to be used in an electrode.

In an embodiment of the present invention, a conductive polymer or a metal oxide is formed on the surface of the porous support so that the porous support can be utilized as an electrode.

Examples of the conductive polymer include Polyacetylene, Polyaniline, Polypyrrole, Polythiophene or Polyethylenedioxythiophene, and examples of metal oxides include vanadium salt, manganese salt, nicotine salt, cobalt salt, iridium salt or ruthenium salt.

In order to form the conductive polymer on the surface of the porous support, a method of immersing the support in the monomer solution of the conductive polymer may be used. After immersion in the monomer solution it is possible to polymerize the conductive polymer through a known polymer polymerization process.

For example, electrochemical oxidative polymerization can be used. The electrochemical oxidative polymerization of the monomer can be carried out at a temperature of -78 ° C to the boiling point of the solvent used. The electrochemical polymerization is preferably carried out at -78 ° C to 250 ° C, particularly preferably at -20 ° C to 60 ° C.

The reaction time is from 1 minute to 24 hours depending on the monomer used, the electrolyte used, the temperature selected and the current density applied.

When the monomer is a liquid, the electropolymerization can be carried out in the presence or absence of a solvent which is inert under the electropolymerization conditions. Electropolymerization of the solid monomers is carried out in the presence of a solvent which is inert under the electropolymerization conditions. In some cases, it may be advantageous to use a solvent mixture and / or add a solubilizer (detergent) to the solvent.

Since the porous support of the present invention forms a three-dimensional structure and is chemically very stable at the same time, the formation of the metal oxide layer on the surface of the support can be performed by an electrochemical method. Specifically, conventionally, as a method for forming a uniform metal oxide layer on a thin film, a method such as sputtering and spin coating, which is generally performed at high temperature and high pressure, is used, which forms a uniform metal oxide layer on a planar substrate. Although it is impossible, for example, to form a uniform metal oxide layer on the surface of the complex shape of the three-dimensional porous structure, when the electrochemical method performed at room temperature and atmospheric pressure is introduced, the complex shape of the three-dimensional porous structure is formed on the substrate. A metal oxide layer can be formed on the substrate.

Therefore, one embodiment of the present invention forms a three-dimensional porous structure, so that the selective use thereof is possible.

In order to form the metal oxide layer, first, a metal oxide electrodeposition liquid is prepared. The metal oxide electrodeposition liquid is a metal salt, in particular, a transition metal salt such as vanadium salt, manganese salt, nickel salt, cobalt salt, iridium salt, ruthenium salt, and the like is dissolved in distilled water. A small amount of an acidic or basic solution, specifically NaOH or H 2 SO 4, is added to the solution to prepare an appropriate pH of 1-10. At this time, the temperature of the metal oxide electrodeposition liquid prepared using a temperature control device is adjusted to 10 ~ 90 ℃, if the temperature is less than 10 ℃ metal oxide is difficult to produce electrochemically and exceeds 90 ℃ Since the problem of evaporation of the electrodeposition liquid occurs, it is preferable to maintain the above range.

The metal oxide layer formed of the metal oxide maintains a thickness in the range of 1 to 200 nm. If the thickness is less than 1 nm, the electrochemical characteristics of the composite electrode of the three-dimensional porous structure manufactured may not be sufficient. In the case of exceeding 200 nm, the metal oxide layer fills pores in the three-dimensional porous structure, and thus it is not possible to maintain the porous structure.

Next, the three-dimensional ceramic porous support is deposited on the metal oxide electrodeposition liquid prepared above.

Next, a metal oxide layer is formed on the support by an electrochemical method to manufacture a composite electrode.

Specifically, the electrochemical method may use a constant current method, an electrostatic potential method, a cyclic current method, and the like, and each of the methods may adjust each factor to freely control the thickness of the metal oxide within the above range.

Specifically, in the constant current method, the applied current is in the range of 0.01 to -100 mA / cm 2, the current application time is in the range of 1 minute to 500 minutes, and the electrostatic potential method is in the range of the applied potential of 0.1 to 1.5 V, and the potential application time is 1 minute to 500. It is in the range of minutes, the cyclic ammeter potential scanning speed is in the range of 1 to 1000 mV / s, and is carried out in the range of 1 to 500 cycles of cyclic potential.

In addition, the electrochemical method is typically carried out at room temperature and atmospheric pressure, which is generally capable of maintaining mild conditions compared to high temperature and high pressure to form a metal oxide layer.

Next, the composite electrode prepared above is subjected to heat treatment at 50 to 400 ° C. for about 1 to 48 hours to increase the electrochemical characteristics of the composite electrode by activating the electrode. If the heat treatment temperature is less than 50 ° C, the activation effect of the electrode is inadequate and if it exceeds 400 ° C, the chemical stability is deteriorated, so it is preferable to maintain the above range.

Another embodiment of the present invention provides a composite electrode including a porous support 202, a conductive polymer 201 and a carbon nanotube 203 as shown in FIG.

Compared with the above-described embodiment as shown in FIG. 1, the embodiment further includes a configuration of the carbon nanotubes 203, in order to increase the specific surface area of the electrode. In order to efficiently increase the size of the surface area and improve the performance of the electrode, the carbon nanotubes are preferably formed perpendicular to the porous support.

The carbon nanotube is formed by forming a growth catalyst layer such as Ni, Co, Fe, etc. on the surface of the porous support by a known method, and a hydrocarbon compound (eg, C ₂ H) by chemical vapor deposition (CVD). ₂ , C ₂ H ₄ , CH ₄ , C ₂ H ₆ ) and the like. In addition, the method of forming carbon nanotubes perpendicular to the support is not limited to the present invention.

The porous support 202 in which the carbon nanotubes 203 are vertically formed may further include a conductive polymer 201 or a metal oxide on its surface as in the above-described embodiment of FIG. 1.

Description of the conductive polymer 201, the metal oxide and the porous support 202 is as described above.

Another embodiment of the present invention provides a composite electrode including a porous support 302, a conductive polymer 301, a carbon nanotube 303 and a plating layer 304 as shown in FIG.

The difference from the above-described embodiment of the present invention is that the porous support 302 is plated with a metal component having excellent conductivity.

The reason for plating the porous support 302 with a metal is to further improve conductivity. Any method can be used in the present invention as long as it can plate the porous support of the three-dimensional structure.

The description of the carbon nanotube 303, the conductive polymer 301, and the porous support 302 is as described above.

Example  One

A composite electrode was prepared using a ceramic filter having Al ₂ O ₃ fibers as its main component. As ceramic paper, Morgan's Kaowool Paper 1260 family was used.

The dried ceramic filter was impregnated into the pyrrole monomer and then chemically polymerized in an iron oxide solution as an oxidizing agent. The polymerized polypyrrole-ceramic filter electrode was washed with water and ethanol and dried again.

8 is a pure ceramic filter before polymerization. 9 is a SEM picture of a polypyrrole-coated ceramic filter after polymerization, FIG. 10 is a picture of a reduced magnification thereof, and FIG. 11 is an enlarged picture of only one ceramic fiber. It can be seen that the polypyrrole is well coated on the ceramic fiber.

Example  2

The composite electrode which used the ceramic filter used in Example 1 as a support body was manufactured. Carbon nanotubes were grown vertically on the surface of the ceramic support using Ni as a growth catalyst and methane gas as a reactive gas on the surface of the support. Ni growth catalyst layer was prepared in a 20-30nm thickness using a sputter. Then, carbon nanotubes were grown by plasma chemical vapor deposition (PECVD). At this time, ammonia gas was used to form a reducing atmosphere, and the vacuum was maintained at 1.2-1.3 torr while flowing at 100-130 sccm. The carbon nanotubes were grown by heating the substrate to 700 ° C. and flowing acetylene gas at 30 sccm for 20 min. Thereafter, polypyrrole was formed on the surface of the ceramic support on which the carbon nanotubes were formed by the method used in Example 1.

Example  3

The surface of the support was plated with silver particles using the ceramic filter used in Example 1 as the support. The plating used a method of sequentially performing electroless copper plating and electroplating.

Formation of carbon nanotubes and polypyrrole after plating was performed in the same manner as in Example 2.

Experimental Example

The polypyrrole-coated ceramic filter prepared in Example 1 was used as an electroactive material, the same ceramic filter used for polymerization was used as a separator, and gold was used as a current collector to measure its electrochemical properties, and the capacitance was calculated. 7 is a schematic diagram of a configured capacitor.

FIG. 12 is a graph obtained by discharging the prepared electrode to a current density of 1 mA at a room temperature of 2 mA. Cm ^-2 , 5 mA.cm ^-2 , and 10 mA.cm ^-2 . Capacitance can be measured using the charging / discharging experiment method. The capacitance can be obtained based on the following equation by selecting a section coming out of a straight line from the discharge curve.

[Equation 1]

C = i · Δt / △ V

i is referred to as the time it takes to sense the current and, as long as the voltage is changed △ △ t of V. When tested by the charge and discharge method, since the current density applied to each electrode and the final voltage reached are constant, the time taken for discharging is an index indicating capacitance. The capacitance calculated through Equation 1 is expressed as a specific capacitance divided by the weight of the electrode material. This can be seen in Table 1.

TABLE 1

It can be seen that the electrode prepared in the charging and discharging experiment has more than 95% charge and discharge efficiency at all measured current densities. Charge and discharge efficiency for each current density is shown in Table 1 above. All of the charge and discharge efficiency was found to be very good, more than 95%.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention as defined in the appended claims. It will be understood that the invention may be varied and varied without departing from the scope of the invention.

Many embodiments other than the above-described embodiments are within the scope of the claims of the present invention.

101: conductive polymer
102: ceramic porous support
201: conductive polymer
202: ceramic porous support
203: carbon nanotube
301: conductive polymer
302: ceramic porous support
303: carbon nanotubes
304: Plating layer

Claims (6)

Ceramic or metal porous supports; And
A conductive polymer or metal oxide formed on the surface of the porous support; Composite electrode comprising a.
Ceramic or metal porous supports;
At least one carbon nanotube formed perpendicular to the surface of the porous support; And
A conductive polymer or metal oxide formed on a surface of the porous support on which the carbon nanotubes are formed;
Composite electrode comprising a.
Ceramic or metal porous supports plated with a highly conductive metal component;
At least one carbon nanotube formed perpendicular to the surface of the plated porous support; And
A conductive polymer or metal oxide formed on a surface of the porous support on which the carbon nanotubes are formed;
Composite electrode comprising a.
The method according to any one of claims 1 to 3,
The ceramic porous support is a composite electrode, characterized in that the ceramic structure having an internal structure of paper or foam form using short fibers, long fibers or ceramic fine particles.
The method according to any one of claims 1 to 3,
The conductive polymer is at least one selected from the group consisting of polyacetylene (Polyacetylene), polyaniline (Polyaniline), polypyrrole (polypyrrole), polythiophene (Polythiophene) and polyethylenedioxythiophene (Polyethylenedioxythiophene).
The method according to any one of claims 1 to 3,
The metal oxide is a composite electrode, characterized in that at least one selected from the group consisting of vanadium salt, manganese salt, nickel salt, cobalt salt, iridium salt and ruthenium salt.

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