KR20200048787A - Electrode for super capacitor, manufacturing method for the same and super capacitor using the same - Google Patents

Abstract

The present invention relates to an electrode, a manufacturing method for the same, and a super capacitor using the same. The present invention includes: a conductive layer applying step of applying a conductive layer containing fine activated carbon having a thickness of 2 um or less on a single or double-sided surface of a metal foil current collector; and an electrode layer applying step of applying an electrode layer including an active material on the surface of the conductive layer. Accordingly, it is possible to obtain an effect that the conductive layer reduces the contact resistance between the metal foil current collector and the electrode layer and improves the charge and discharge output characteristics and long-term reliability of the supercapacitor using the same.

Description

Electrode, its manufacturing method and supercapacitor using the same {ELECTRODE FOR SUPER CAPACITOR, MANUFACTURING METHOD FOR THE SAME AND SUPER CAPACITOR USING THE SAME}

The present invention relates to an electrode, a method for manufacturing the same, and a supercapacitor using the same, and more specifically, to apply a conductive layer containing fine activated carbon to one or both surfaces of a metal foil current collector, and to apply an electrode layer to the surface of the conductive layer. It relates to an electrode having reduced contact resistance by coating and a supercapacitor having improved output characteristics using the same.

In general, the supercapacitor can be broadly classified into an electric double layer capacitor using a polarizable electrode for an anode and a cathode, and a hybrid capacitor composed of a polarizable electrode and an electrode for a secondary battery based on a chemical reaction.

Unlike secondary batteries that use chemical reactions between electrodes and electrolytes, supercapacitors use a charge storage power supply using at least one of the positive electrode and the negative electrode, which uses the interface reaction of activated carbon, resulting in high output density, charging and discharging efficiency, and long-term reliability. great.

The electrochemical properties of supercapacitors are affected by materials and parts such as metal foil current collectors, active materials, and electrolytes, but are also greatly affected by the surface condition and the degree of contact between these materials.

In the case of an aluminum foil current collector for a supercapacitor, etched aluminum mainly manufactured by electrolytic etching on the surface of aluminum is used. In general, the surface roughness of the etched aluminum serves to improve mechanical and electrical conductivity by imparting a binding force with an electrode containing activated carbon.

However, the water-repellent film on the surface created in the etching process gradually deteriorates or becomes thicker into an aluminum oxide film by reaction with moisture present in the electrolytic solution or activated carbon pores during repeated charging and discharging processes after being left in the air for a long time or after cell assembly. It acts as the contact resistance of the bonding surface.

In the case of an electric double layer capacitor in which a polarizable electrode is used for the positive electrode and the negative electrode, moisture contained in the electrolyte or the like is electrolyzed at the negative electrode during aging to generate an alkali component. In addition, since the oxide film existing on the surface of the current collector dissolves by the alkali component, and the negative electrode becomes a negative potential than the aluminum electrolytic potential during discharge, a reaction as shown in Reaction Formula 1 occurs inside the aluminum current collector. This reaction is especially the anion BF ₄ used for the ^electrolyte and the like even if there is acceleration, at the same time compounds such as Scheme 2, the negative electrode ^formed-F of hydrolysis products.

[Scheme 1]

Al → Al ³⁺ + 3e ^-

[Scheme 2]

Al ³⁺ + 3F ^- → AlF ₃

Since the process of the substrate is more reactive at high temperature, the integration of the product is deepened and acts as a cause of increasing the internal resistance.

As a method for suppressing the surface corrosion of aluminum, Japanese Patent Application No. 10-2014-207619 (Patent Document 1) shows an aluminum etching foil manufacturing method of forming a film containing phosphorus (P) by anodic oxidation Did. This patent is a chemically inert phosphoric acid compound Al (PO ₄ ), Al ₂ (HPO ₄ ) ₃ , Al (H ₂ PO ₄ ) ₃ by depositing an aluminum current collector in a solution containing a phosphoric acid compound and anodizing it. It provides a method of forming.

However, since it is easy to have a film thickness of about 100 μm or more of these phosphoric acid compounds, there is a problem in that the cell internal resistance increases due to a decrease in electrical conductivity.

On the other hand, Japanese Patent Application No. 10-2013-0216596 (Patent Document 2) has a research case of forming a conductive resin layer to reduce the contact resistance between the aluminum foil current collector and the electrode layer containing the active material. In the literature, a conductive resin layer solution containing a polymer, a conductive material, a crosslinking agent, and a dispersant having a group bonded with an active hydrogen group for the purpose of suppressing the peeling of the conductive resin layer and suppressing the deterioration of the charging device properties, and preparing an aluminum foil current collector. It is shown to be applied to the surface.

However, the method for preventing the surface corrosion of the metal foil current collector or the conductive resin layer shown in the patent documents has an effect of suppressing an increase in resistance due to long-term use of a supercapacitor to which these methods are applied, but the metal foil current collector and an active material There is a limit to reduce the contact resistance with the electrode layer comprising a.

In particular, the conductive resin layer such as Patent Document 2 includes a polymer binder for the purpose of improving the applicability and binding properties, but these polymer binders cover the surface of a carbon material such as carbon black or graphite included in the conductive resin layer. There are limits to improving contact resistance.

Therefore, a method for solving such a problem is required.

Japanese Patent Application 10-2014-207619 Japanese Patent Application 10-2013-0216596

The technical problem of the present invention is to solve the problems mentioned in the background art, and more specifically, a conductive layer containing activated carbon having an average particle diameter of 2 μm or less is applied to at least one surface of one or both surfaces of a metal foil current collector. And by pressing at a predetermined pressure to produce a conductive layer having excellent binding power and excellent electrical conductivity, and forming an electrode layer containing an active material on the surface of the conductive layer, an electrode having excellent output characteristics, a method for manufacturing the same, and a supercapacitor using the same It aims to provide.

The technical problems to be achieved by the present invention are not limited to the technical problems mentioned above, and other technical problems not mentioned can be clearly understood by those skilled in the art from the following description. There will be.

A method for manufacturing an electrode for a supercapacitor according to the present invention devised to solve a technical problem, a conductive layer coating step of applying a conductive layer containing fine activated carbon having a thickness of 2 μm or less to a single or double-sided surface of a metal foil current collector and the conductive layer It may include an electrode layer application step of applying an electrode layer containing an active material on the surface.

The metal foil current collector may be selected from the group consisting of aluminum (Al), copper (Cu), nickel (Ni), stainless steel, tantalum (Ta), platinum (Pt), and mixtures thereof.

The fine activated carbon of the conductive layer has a specific surface area in the range of 500 to 4,000 m ² / g, and can be obtained by selecting and grinding any one of a rotary mill, a planetary mill, an atrium mill, a rod mill, and a jet mill.

The conductive layer may further include a conductive material.

The conductive material may be selected from the group consisting of carbon black, carbon nanotubes, carbon nanofibers, graphite, graphene and mixtures thereof.

The conductive layer is a slurry of the fine activated carbon, the conductive material and the binder together with a solvent, the weight ratio of the fine activated carbon is 75 to 95% based on the solid content, the weight ratio of the conductive material is 3 to 20%, and the binder is 2 to It may be desirable to be 5%.

The conductive layer may preferably have a thickness of 2 μm or less after being pressed.

On the other hand, the electrode for a supercapacitor according to the present invention is applied to a metal foil current collector, one or both surfaces of the metal foil current collector, and is formed on a conductive layer containing fine activated carbon and the surface of the conductive layer, and includes an active material. It may be configured to include an electrode layer.

Meanwhile, the supercapacitor according to the present invention may include a supercapacitor electrode manufactured according to a method for manufacturing an electrode for a supercapacitor.

According to the above-described configuration of the present invention, the conductive layer may have an effect of reducing the contact resistance between the metal foil current collector and the electrode layer, and may have an effect of improving charge / discharge output characteristics and long-term reliability of the supercapacitor using the same. have.

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

Hereinafter, embodiments of the present invention will be described in detail. However, this is provided as an example, and the present invention is not limited thereby, and the present invention is only defined by the scope of claims to be described later. In addition, in describing the present invention, descriptions of already known functions or configurations will be omitted to clarify the gist of the present invention.

In general, the metal foil current collector is selected according to the electrochemical mechanism of the supercapacitor and the electrolytic solution, and the metal foil current collector for an electric double layer capacitor or hybrid capacitor using an organic solution has an aluminum (Al) current collector at the anode and aluminum at the cathode. Alternatively, a copper (Cu) current collector is used, and aluminum is mainly used for etching aluminum. As a pseudo capacitor, an electric double layer capacitor, or a hybrid capacitor using an alkaline or acidic aqueous solution, nickel (Ni), stainless (Stainless steel), tantalum (Ta) or platinum (Pt) current collectors may be used.

The electrode layer containing the active material on one or both surfaces of the metal foil current collector is generally prepared by slurry coating. In the case of the polarizable electrode, the aluminum foil current collector is used for etching to improve the binding force and electrical conductivity between the metal foil current collector and the electrode layer. The etching feet generated during the etching process of the aluminum foil current collector improve the binding force with the electrode layer, and the water-repellent film formed on the surface serves to maintain electrical conductivity with the electrode layer.

On the other hand, in order to improve the binding force between the aluminum foil current collector and the electrode layer, a conductive layer made of a conductive material and a binder is applied to the surface of the metal foil current collector.

The above-described conductive layer generally uses an additive such as a crosslinking agent and one or more polymer binders and dispersants with a large number of molecules to improve the coatability and adhesion, and as a conductive material, graphite, graphene, carbon nanotubes and carbon having a shape aspect ratio of 0.1 or more Nanofibers or carbon blacks having an average particle size of 0.1 μm or less have been mixed and used.

However, the aforementioned conductive layer has a disadvantage in that the manufacturing cost is high because the process involves a complicated process such as melting, polymerization, or mixing, and the coated conductive layer improves the binding strength with the electrode layer but the binder coats the conductive material. Accordingly, there is a limit in improving conductivity between the metal foil current collector and the electrode layer.

Accordingly, the present invention, to improve the output characteristics of the electrode for a supercapacitor using a metal foil current collector, a slurry comprising fine activated carbon having an average particle diameter of 2 μm or less on at least one surface of one or both surfaces of the metal foil current collector It is an object of the present invention to provide a conductive layer having excellent binding force by applying and pressing, and to provide an electrode forming an electrode layer containing an active material on the surface of the conductive layer, a method for manufacturing the same, and a supercapacitor using the same.

First, a method of manufacturing an electrode for a supercapacitor according to the present invention will be described in detail.

The electrode manufacturing method according to the present invention may include a conductive layer applying step and an electrode layer applying step.

The conductive layer coating step is a step of applying a conductive layer containing fine activated carbon having a thickness of 2 μm or less on one or both surfaces of the metal foil current collector.

The metal foil current collector may be preferably selected from the group consisting of aluminum (Al), copper (Cu), nickel (Ni), stainless steel, tantalum (Ta), platinum (Pt), and mixtures thereof. .

In addition, the fine activated carbon of the conductive layer has a specific surface area in the range of 500 to 4,000 m ² / g, and it is preferable to pulverize by selecting any one of a rotary mill, a planet mill, an atrium mill, a rod mill, and a jet mill.

In general, activated carbon is obtained through an activation process of petroleum, coal-based by-products obtained from the steelmaking and steelmaking processes, or wood-based raw materials obtained from nature, and has pores developed in the activation process. And the specific surface area of the activated carbon is in the range of 500 to 4,000 m ² / g, and the larger the specific surface area, the easier the crushing.

Activated carbon can generally be pulverized by using a rotary mill, a planetary mill, an atrium mill, a rod mill and a jet mill with an average particle diameter in the range of 5 to 200 μm, and the pulverization is a dry method in which only activated carbon powder is charged and milled. Or, it may be done by selecting the wet method of loading the powder with the solution into the container. Activated carbon has an average particle size that varies depending on the grinding time and conditions, but it is generally possible to control the average particle size in the range of 0.1 to 2 μm. Activated carbon having an average particle diameter of 0.1 μm or less has a small effect of being pressed into the surface of a metal foil current collector during the pressing process, and activated carbon having an average particle diameter of 2 μm or more has a problem in that coating is not uniform, so that the activated carbon of the fine activated carbon according to the present invention The average particle size is preferably in the range of 0.1 to 2 μm.

On the other hand, activated carbon can be obtained from bi-graphitizable carbon and non-graphitizable carbon, respectively. These graphitizable carbons include petroleum coke, coal pitch coke, polyvinyl chloride charcoal, and 3.5 dimethyl phenol rhodium aldehyde resin charcoal, and carbon black, polyvinylidene chloride, sugar charcoal, cellulose, etc. There may be coal, phenol formaldehyde resin charcoal, and the like.

The harder the degree of hard carbon is, the greater the number of non-graphitizable raw materials, or the larger the specific surface area of activated carbon activated with these non-graphitizable raw materials, the easier the crushing and the sharper the crushing surface. Graphite, graphene, nano-carbon tubes, and nano-carbon fibers with mostly SP ₂ structure on carbon black and exposed surfaces have mostly round or plate-like surfaces, so these materials have little effect of being pressed into the metal foil current collector during the pressing process. .

However, the fine activated carbon used in the present invention is hard and has a sharp crushed surface to form a conductive layer on the surface of the metal foil current collector, and thus has an excellent indentation effect in the press process described later, and some are formed on the surface of the metal foil current collector. It may be pressed through the oxide film. In the case of aluminum, the oxide film is about 30 MPa in the state of natural oxidation, and thus the contact resistance can be improved by allowing the activated carbon to penetrate and press these oxide films.

Therefore, in the electrode manufacturing method according to the present invention, the conductive layer application step may include a pressing process of applying the conductive layer to the metal foil current collector and pressing the fine activated carbon by press. It may be formed to press the current collector surface. At this time, it is preferable that the thickness of the conductive layer is 2 μm or less after pressing.

Meanwhile, the conductive layer of the electrode according to the present invention may be further formed of a conductive material.

At this time, the conductive material is preferably selected from the group consisting of carbon black, carbon nanotubes, carbon nanofibers, graphite, graphene and mixtures thereof.

In this case, the conductive layer is a slurry of a fine activated carbon, a conductive material and a binder together with a solvent, and the weight ratio of the fine activated carbon is 75 to 95%, the weight ratio of the conductive material is 3 to 20%, and the binder is 2 to 5 based on solid content. %.

More specifically, in order to impart more conductivity to the conductive layer composed of the fine activated carbon and the binder in the present invention, some conductive carbon may be added in place of the fine activated carbon. At this time, as the conductive material, one or more conductive materials of carbon black having an average particle diameter of 0.1 μm or less, or graphite, graphene, carbon nanotubes, and carbon nanofibers having a shape aspect ratio of 0.1 or more may be used.

Here, the binder is usually applied to electrodes for supercapacitors, such as PTFE (Polytetrafluoroethylene), CMC (Carboxymethylcellulose), PVA (Polyvinyl alcohol), PVDF (Polyvinyliene fluoride), PVP (Polyvinylpyrrolidone), MC (methyl cellulose), and latex series. Ethylene-vinyl chloride copolymer resin, vinylidene chloride latex, chlorinated resin, vinyl acetate resin, polyvinyl butyral, polyvinyl formal, bisphenol-based epoxy resin and Styrene Butadiene Rubber (SBR) series butadiene rubber, isoprene rubber, nitrile butadiene It may include one or more of rubber, urethane rubber, silicone rubber, and acrylic rubber.

When manufacturing a slurry composed of fine activated carbon, a conductive material and a binder, the binder serves to control the viscosity and dispersion degree of the slurry composed of a fine activated carbon and a conductive material, and aims to improve the applicability to the surface of the metal foil current collector. Have However, in the slurry of the base material, the fine activated carbon is physically bound to the metal foil current collector in the press process, and the surface of the conductive layer containing the fine activated carbon has a roughness, so that the binding force with the electrode layer is also improved. Therefore, the binder included in the conductive layer according to the present invention has a simpler component and process than the conventional commercial conductive layer slurry, and a binder applied to an electrode for a supercapacitor can be commonly used.

The slurry is a mixture of a fine activated carbon powder and a conductive material dissolved in a solvent, and the viscosity can be adjusted to 200 to 1,000 cp or less during the stirring process. As described above, it is preferable that the weight ratio of the fine activated carbon is 75 to 95%, the weight ratio of the conductive material is 3 to 20%, and the binder is 2 to 5%, based on the solid content, as described above.

In order to improve the degree of dispersion during mixing or when the slurry is left, a dispersant may be used for the isopropyl alcohol, and a weight ratio of 2 to 10% may be substituted for the solvent.

The conductive layer can be adjusted to a thickness of 2 μm or less by applying the slurry to one or both sides of the metal foil current collector through a gravure coating machine, drying it at a temperature of 100 ° C. or less in the atmosphere, and pressing it. The press can be used by selecting a hot press or cold press of 120 ° C or less.

Meanwhile, in the electrode manufacturing method according to the present invention, the electrode layer application step is a step of applying an electrode layer containing an active material on the surface of the conductive layer.

More specifically, on the surface of the conductive layer, a lithium metal oxide, activated carbon, and graphite powder, which are electrode materials of a supercapacitor, are coated with a slurry with a conductive material and a binder to apply an electrode layer, and after drying, press with a predetermined pressure to form an electrode. Can be.

In the case of an electric double layer capacitor using a polarizable electrode for an anode and a cathode, a conductive layer containing fine activated carbon is applied to the surface of an aluminum current collector, and then an electrode layer containing activated carbon is applied to form an electrode, and presses each conductive layer. It may be carried out after application of the over-electrode layer, or may be carried out after successive application of the conductive layer and the electrode layer.

The electrode layer may include activated carbon, and the activated carbon of the electrode layer is commercially available. The average particle diameter is in the range of 5 to 20 μm, and the specific surface area can be used in the range of 1,500 to 4,000 m ² / g. The electrode layer containing activated carbon constitutes an electrode slurry using a conductive material and a binder, and is applied to the surface of the conductive layer containing fine activated carbon.

The conductive material composed of the electrode layer can be used including one or more of carbon black, graphite, graphene, nanocarbon tubes, and nanocarbon fibers, but has a large dispersion effect in the electrode slurry, and carbon to increase the filling density of the applied electrode layer. It is preferred to use black.

The binder composed of the electrode layer is typically applied to electrodes for supercapacitors, such as PTFE (Polytetrafluoroethylene), CMC (Carboxymethylcellulose), PVA (Polyvinyl alcohol), PVDF (Polyvinyliene fluoride), PVP (Polyvinylpyrrolidone), MC (methyl cellulose), and latex. A series of ethylene-vinyl chloride copolymer resins, vinylidene chloride latex, chlorinated resin, vinyl acetate resin, polyvinyl butyral, polyvinyl formal, bisphenol-based epoxy resin and Styrene Butadiene Rubber (SBR) series butadiene rubber, isoprene rubber, Nitrile butadiene rubber, urethane rubber, silicone rubber, and acrylic rubber.

The component ratio of the electrode slurry can be selected from 76 to 95% by weight of activated carbon, 2 to 7% by weight of conductive material, and 3 to 7% by weight of binder based on solid content, and the slurry is activated carbon and conductive material in a binder dissolved in a solvent. It is prepared by adding and stirring. The viscosity can be adjusted in the range of 700 to 2,000 cp.

The electrode layer can be adjusted to a thickness of 100 μm or less by applying the slurry to the surface of the conductive layer through a coating machine, drying it at a temperature of 100 ° C. or less in the atmosphere, and pressing it. As the thickness of the electrode layer decreases, the ion diffusion resistance of the electrode decreases, but the filling capacity of the cell decreases. In the case of a commercial electric double layer capacitor, the thickness of the electrode layer is adjusted and used in a range of 60 to 90 μm.

In the above-described configuration, the electrode according to the present invention increases the contact area by pressurizing the hard fine activated carbon contained in the conductive layer on the surface of the current collector, and in the press-fitting process, the contact surface can exclude the binder component, thereby metal foil collection It is possible to reduce the contact resistance between the whole and hard fine activated carbon.

In addition, the surface of the conductive layer including the fine activated carbon pressed into the surface of the metal foil current collector in the pressing process has a roughness, and the electrode layer coated on the surface of the conductive layer improves the degree of binding with the conductive layer and also improves conductivity. It has the effect of being.

Hereinafter, preferred embodiments of the present invention will be described. However, the following examples are only preferred embodiments of the present invention, and the invention is not limited to the following examples.

<Example>

In the Examples and Comparative Examples of the present invention, a method of manufacturing a conductive layer, an electrode layer, and an electric double layer capacitor using the same, and an electrical or electrochemical evaluation method formed on the surface of the metal foil current collector are as follows.

(Method of manufacturing a conductive layer)

(a) Activated carbon crushing: Using a coconut shell as a raw material, activated carbon having a specific surface area of 1,700 m ² / g and an average particle size of 8 μm was pulverized with a rotary ball mill together with a ZrO ₂ ball having a diameter of 10 mm Φ. The ball and the activated carbon powder were charged to a stainless steel container of about 2 L in a weight ratio of 30: 1, respectively, and milling was performed in an atmosphere.

(b) Slurry for the conductive layer: 3 g of isopropyl alcohol was added to a solution in which 2 g of CMC (Carboxymethylcellulose) was dissolved in 95 g of distilled water and dispersed for 30 minutes with ultrasonic waves. 5.25 g of activated carbon powder having an average particle diameter of 1 μm and carbon black in a mixed solution 1.75 g was added and stirred at 1800 rpm for 10 minutes in a mixer (Thinky mixser) and defoamed to prepare a slurry.

(c) Preparation of the conductive layer: The slurry for the conductive layer was continuously applied to a surface of an aluminum foil current collector having a thickness of 20 μm with a gravure coater and dried with hot air at 50 ° C. The dried conductive layer was pressed to a final thickness of 1.0 μm by a 3 ton roll press.

(Method of manufacturing the electrode layer)

(a) Slurry for the electrode layer: 37.5 g of CMC and 0.5 g of SBR dispersed in a 2% weight ratio of distilled water were added to the reactor, followed by stirring at 1800 rpm for 10 minutes with a thin mixer. 1.75 g of carbon black, a conductive material, was added to the reactor, followed by 10 minutes of sonication, followed by stirring with a thinky mixer (1800 rpm) for 10 minutes. Finally, 22 g of activated carbon powder having a specific surface area of 1,700 m ² / g and an average particle diameter of 8 μm was mixed in a reactor, stirred at 1800 rpm for 10 minutes in a mixer and defoamed for 5 minutes to prepare a slurry.

(b) Preparation of electrode layer: The electrode layer slurry was coated with a doctor blade on the surface of the aluminum foil current collector or the aluminum foil coated with the conductive layer. The coated electrode was vacuum dried at a temperature of 150 ° C. for 24 hours, and then pressed with a roll press (120 ° C.) until the electrode thickness was 80 μm and the electrode density was 0.6 g / cc to prepare an electrode layer.

(Electric double layer capacitor cell manufacturing method)

The electrode was cut to 2.5 x 2.5 cm2, and one end surface of the current collector to which the electrode was not attached was cut long in the longitudinal direction to be used as a terminal. The electrode is vacuum dried at 120 ° C. for 12 hours and then laminated in the order of 'single-carbon electrode / isolation film / single-carbon electrode' using a separator (Seperator, TF4035, Japan High Purity Industry Co., Ltd.) and a laminated polymer pouch with three sides sealed. Then, it was inserted into a polymer pouch. After that, in an electrolyte injector capable of vacuum decompression and pressure, an electrolyte solution in which 1.2 M quaternary ammonium salt (Et ₄ NBF ₄ ) was dissolved in acetonitrile (AcN) was impregnated and vacuum sealed to prepare a pouch type electric double layer capacitor cell. .

<Measurement method>

(Electric resistivity)

Cylindrical terminals made of gold (Au) were pressed on the top and bottom of the electrode and evaluated by a 4-terminal resistance measurement method, and the electrical resistivity of the electrode was calculated by Equation 1 below.

[Equation 1]

In Equation 1, V is voltage, I is current, A is cylindrical terminal area, and l is electrode thickness.

(Average particle size)

The pulverized activated carbon particles were evaluated for particle size through a particle size analyzer, and the particle size of D50 was expressed as an average particle size.

(Discharge capacity)

The electric double layer capacitor cell was charged and discharged in a charge / discharge tester (Maccor, model name Series 4000). The driving voltage was in the range of 0 to 2.7 V, and the applied current density was a constant current charging and discharging experiment with a current density of ² mA / cm ² . The discharge specific capacity was calculated by dividing the capacity (F) obtained by Equation 2 below by the weight (g) of the activated carbon in the time-voltage curve at the tenth constant current discharge.

[Equation 2]

In Equation 2, I is current, dt is time, and dV is a voltage section.

(AC resistance)

The AC resistance of the cell was measured in the range of 100 to 0.01 kHz using an AC impedance tester (Zahner IM6), and the equivalent series resistance (ESR) of the cell was expressed as 1 kHz resistance.

(Capacity retention rate)

To proceed with accelerated deterioration, the electric double layer capacitor cell, which was repeatedly charged and discharged 5 times in the range of 0 to 2.7 V at room temperature, maintains 50 hours after charging 3.5 V at 60 ° C., discharges to 0 V and then discharges to 0 V at room temperature. Charging and discharging were repeated 5 times in the 2.7V range. The capacity retention rate was expressed as the retention rate (%) of the fifth discharge capacity after accelerated deterioration compared to the initial fifth discharge capacity.

<Example 1>

On the surface of the 20 μm thick aluminum foil current collector, a slurry containing activated carbon having an average particle diameter of 1 μm and carbon black having an average particle diameter of 50 nm was applied and dried to form a conductive layer having a thickness of 1.5 μm. An electrode layer containing activated carbon having an average particle diameter of 8 μm was applied to the surface of the conductive layer, dried and roll-pressed to prepare an electrode, and the specific resistance of the electrode was measured. Electrical double-layer capacitors having these electrodes disposed on positive and negative electrodes were prepared, and cell resistance, discharge capacity, and capacity retention were measured and are shown in Table 1.

<Example 2>

On the surface of the aluminum foil current collector having a thickness of 20 μm, a slurry containing activated carbon having an average particle diameter of 1 μm and carbon black having an average particle diameter of 50 nm was applied, dried, and then roll-pressed to form a conductive layer having a thickness of 1 μm. An electrode layer containing activated carbon having an average particle diameter of 8 μm was applied to the surface of the conductive layer, dried and roll-pressed to prepare an electrode, and the specific resistance of the electrode was measured. Electrical double-layer capacitors having these electrodes disposed on positive and negative electrodes were prepared, and cell resistance, discharge capacity, and capacity retention were measured and are shown in Table 1.

<Example 3>

On the surface of the aluminum foil current collector having a thickness of 20 μm, a slurry containing carbon black having an average particle diameter of 50 nm was applied and dried to form a conductive layer having a thickness of 0.6 μm. An electrode layer containing activated carbon having an average particle diameter of 8 μm was applied to the surface of the conductive layer, dried and roll-pressed to prepare an electrode, and the specific resistance of the electrode was measured. Electrical double-layer capacitors having these electrodes disposed on positive and negative electrodes were prepared, and cell resistance, discharge capacity, and capacity retention were measured and are shown in Table 1.

<Example 4>

A slurry containing carbon black having an average particle diameter of 50 nm was applied to the surface of an aluminum foil current collector having a thickness of 20 μm, dried, and roll-pressed to form a conductive layer having a thickness of 0.5 μm. An electrode layer containing activated carbon having an average particle diameter of 8 μm was applied to the surface of the conductive layer, dried and roll-pressed to prepare an electrode, and the specific resistance of the electrode was measured. Electrical double-layer capacitors having these electrodes disposed on positive and negative electrodes were prepared, and cell resistance, discharge capacity, and capacity retention were measured and are shown in Table 1.

<Comparative Example 1>

An electrode layer containing activated carbon having an average particle diameter of 8 μm was applied to a surface of an aluminum foil current collector having a thickness of 20 μm, dried and roll-pressed to prepare an electrode, and the specific resistance of the electrode was measured. Electrical double-layer capacitors having these electrodes disposed on positive and negative electrodes were prepared, and cell resistance, discharge capacity, and capacity retention were measured and are shown in Table 1.

<Comparative Example 2>

An electrode layer containing activated carbon having an average particle diameter of 8 μm was applied to a surface of an etching aluminum foil current collector having a thickness of 20 μm, dried, and roll-pressed to prepare an electrode, and the specific resistance of the electrode was measured. Electrical double-layer capacitors having these electrodes disposed on positive and negative electrodes were prepared, and cell resistance, discharge capacity, and capacity retention were measured and are shown in Table 1.

Table 1 shows electrode resistivity (Ωcm), cell resistance (mΩ), discharge specific capacity (F / g), and capacity retention rate (%), respectively, of the comparative example and the embodiment according to the present invention.

Electrical resistivity
(Ωcm)
Cell resistance @ 1kHz
(mΩ)
Discharge specific capacity @ 10th
(F / g)
Capacity retention rate
(%)
Example 1
48
71
30
80
Example 2
38
60
31
90
Example 3
42
65
30
82
Example 4
41
65
32
83
Comparative Example 1
55
75
30
52
Comparative Example 2
40
75
32
85

Table 1 shows the electrode resistivity (Ωcm), cell resistance (mΩ), discharge specific capacity (F / g), and capacity retention rate (%) of the comparative example and the embodiment according to the present invention, respectively.

Compared to Example 1, the electrical resistivity of Example 2 was reduced by about 21%, and the cell resistance and capacity retention rate were improved. This is judged to be due to pressurization of the fine activated carbon on the surface of the aluminum foil current collector in the process of roll pressing the conductive layer in Example 2. Fine activated carbon with a sharp crushing surface may tear and enter the oxide film of some aluminum foil current collectors during roll pressing. These contact surfaces are excellent in adhesion and also serve to reduce electrical resistivity by increasing the total contact area, but the contact surfaces block contact with the solution to suppress corrosion of the aluminum foil current collector.

Examples 3 and 4 were coated with a conductive layer containing carbon black having an average particle diameter of 50 nm, and exhibited similar electrical resistivity and electrochemical properties regardless of whether the conductive layer was roll pressed or not. When only carbon black was included in the conductive layer, the effect of the roll press of the conductive layer was not confirmed.

Comparative Example 1 and Comparative Example 2 is a method of manufacturing an electrode that does not include a conductive layer, and Comparative Example 2 using etched aluminum is a method of manufacturing an electrode applied in a commercial electric double layer capacitor manufacturing method. The comparative example shows high electrical resistivity and low electrochemical properties compared to Example 2.

From the above results, it can be seen that when the conductive layer containing hard fine activated carbon is applied and pressed, the contact resistance of the electrode is reduced by the indentation effect of the fine activated carbon, and electrochemical properties such as cell resistance and capacity retention are improved. .

The electrode manufacturing method according to the present invention has been described above in detail, and the electrode according to the present invention will be described below. Here, since the configuration of the electrode to be described later is as described above, detailed description thereof will be omitted.

The electrode according to the present invention is manufactured by the above-described electrode manufacturing method, and may include a metal foil current collector, a conductive layer, and an electrode layer.

The metal foil current collector is preferably selected from the group consisting of aluminum (Al), copper (Cu), nickel (Ni), stainless steel, tantalum (Ta), platinum (Pt), and mixtures thereof.

In addition, the conductive layer is applied to one or both surfaces of the metal foil current collector, and may include fine activated carbon.

In this case, the conductive layer may further include a conductive material, and the conductive material is preferably selected from the group consisting of carbon black, carbon nanotubes, carbon nanofibers, graphite, graphene, and mixtures thereof.

On the other hand, the conductive layer is a slurry of a fine activated carbon, a conductive material and a binder together with a solvent, based on solid content, the weight ratio of the fine activated carbon is 75 to 95%, the weight ratio of the conductive material is 3 to 20%, and the binder is 2 to 5 %.

Here, the binder is PTFE (Polytetrafluoroethylene), CMC (Carboxymethylcellulose), PVA (Polyvinyl alcohol), PVDF (Polyvinyliene fluoride), PVP (Polyvinylpyrrolidone), MC (methyl cellulose), ethylene-vinyl chloride copolymer resin, vinylidene chloride latex, chlorinated It is preferable to include at least one of resin, vinyl acetate resin, polyvinyl butyral, polyvinyl formal, bisphenol-based epoxy resin, butadiene rubber, isoprene rubber, nitrile butadiene rubber, urethane rubber, silicone rubber and acrylic rubber.

Then, the conductive layer and the metal foil current collector are pressed, whereby the fine activated carbon of the conductive layer may be configured to be pressed into the surface of the metal foil current collector.

In such a configuration, the contact area is widened by the pressurization of the fine activated carbon on the surface of the current collector, and the binder component is excluded from the contact surface, whereby an effect of reducing the contact resistance between the metal foil current collector and the fine activated carbon can be obtained.

And, the electrode layer is formed on the surface of the conductive layer, and is composed of an active material.

Since the surface of the conductive layer including the fine activated carbon pressed into the surface of the metal foil current collector has a roughness, the electrode layer coated on the surface of the conductive layer may have an effect of improving the degree of binding with the conductive layer and also improving the conductivity. have.

Meanwhile, the supercapacitor according to the present invention can be formed to use the electrode according to the present invention. Therefore, the conductive layer may have an effect of reducing the contact resistance between the metal foil current collector and the electrode layer, and improving the charge and discharge output characteristics and long-term reliability of the supercapacitor using the same.

As described above, the preferred embodiments according to the present invention have been examined, and the fact that the present invention may be embodied in other specific forms without departing from the spirit or scope of the embodiments described above has ordinary knowledge in the art. It is obvious to them. Therefore, the above-described embodiments should be regarded as illustrative rather than restrictive, and accordingly, the present invention is not limited to the above description and may be changed within the scope of the appended claims and their equivalents.

Claims (9)

A conductive layer coating step of applying a conductive layer containing fine activated carbon having a thickness of 2 μm or less on one or both surfaces of the metal foil current collector; And
An electrode layer applying step of applying an electrode layer containing an active material on the surface of the conductive layer;
Supercapacitor electrode manufacturing method comprising a. According to claim 1,
The metal foil current collector,
Aluminum (Al), copper (Cu), nickel (Ni), stainless steel (Stainless steel), tantalum (Ta), platinum (Pt), and a method for manufacturing an electrode for a supercapacitor electrode, characterized in that selected from the group consisting of a mixture thereof . According to claim 1,
The fine activated carbon of the conductive layer,
Specific surface area in the range of 500 to 4,000 m ² / g,
A method for manufacturing an electrode for a supercapacitor, comprising grinding by selecting one of a rotary mill, a planetary mill, an atrium mill, a rod mill and a jet mill. According to claim 1,
The conductive layer,
A method for manufacturing an electrode for a supercapacitor, further comprising a conductive material. The method of claim 4,
The conductive material is carbon black, carbon nanotubes, carbon nanofibers, graphite, graphene, and a method for manufacturing an electrode for a supercapacitor, characterized in that is selected from the group consisting of a mixture thereof. The method of claim 4,
The conductive layer is a slurry of the fine activated carbon, the conductive material and a binder together with a solvent,
A method for manufacturing an electrode for a supercapacitor, wherein the weight ratio of the fine activated carbon is 75 to 95%, the weight ratio of the conductive material is 3 to 20%, and the binder is 2 to 5% based on solid content. According to claim 1,
After the conductive layer is pressed, the method for manufacturing an electrode for a supercapacitor is characterized in that the thickness is 2μm or less. The electrode for a supercapacitor manufactured according to the method for manufacturing an electrode for a supercapacitor according to any one of claims 1 to 7,
Metal foil current collector;
A conductive layer coated on one or both surfaces of the metal foil current collector and comprising fine activated carbon; And
An electrode layer formed on the surface of the conductive layer and including an active material;
Electrode for a supercapacitor comprising a. A supercapacitor using an electrode for a supercapacitor manufactured according to the method for manufacturing an electrode for a supercapacitor according to any one of claims 1 to 7.