KR102157384B1 - Electrical double layer capacitor including granular activated carbon-carbon nanotube composite - Google Patents

Abstract

Disclosed is an electrical double layer capacitor including a granular activated carbon-carbon nanotube composite, which improves conductivity and ESR properties and improves energy density by applying the granular activated carbon-carbon nanotube composite as an electrode active material. According to the present invention, the electrical double layer capacitor including the granular activated carbon-carbon nanotube composite includes: a case with open-top which is impregnated with an electrolyte solution; a winding element inserted and disposed into the case and having a cathode, an anode, and a separator which is disposed between the cathode and anode and electrically separates the cathode and anode; and a sealing rubber coupled to the top of the case to seal inside the case. As the active material of each of the anode and cathode, the granular activated carbon-carbon nanotube composite having an average particle diameter of 10 to 50 um is used.

Description

Electric double layer capacitor including granular activated carbon-carbon nanotube composite {ELECTRICAL DOUBLE LAYER CAPACITOR INCLUDING GRANULAR ACTIVATED CARBON-CARBON NANOTUBE COMPOSITE}

The present invention relates to an electric double layer capacitor comprising a granular activated carbon-carbon nanotube composite, and more particularly, by applying a granular activated carbon-carbon nanotube composite as an electrode active material, improving conductivity and ESR characteristics, and energy It relates to an electric double layer capacitor comprising a granular activated carbon-carbon nanotube composite capable of improving the density.

Electric Double Layer Capacitor (EDLC) has a separator (separator, separator or separator), and the anode and cathode are arranged opposite to each other, so that a pair of charge layers (electric double layers) with different codes are created on the opposite surface. As an energy storage medium using the device, it is a device capable of continuous charging/discharging.

Such electric double layer capacitors are mainly used as auxiliary power supplies for various electric and electronic devices, and IC backup power supplies. Recently, electric double layer capacitors have been widely applied to toys, industrial power supplies, uninterrupted power supply (UPS), solar energy storage, HEV/EV sub power, and the like.

In the electric double layer capacitor, a material with a large surface area such as activated carbon is used as an active material of an electrode to form an electric double layer on the surface of the electrode material and the contact surface of the electrolyte. Electric double layer capacitors store electric charges in the electric double layer formed at the interface of the electrolyte, unlike storage batteries that use chemical reactions in the mechanism of storing electricity, i.e., due to the use of a storage phenomenon due to the accumulation of physical charges, deterioration due to repeated use No phenomenon, high reversibility and long service life.

Activated carbon is commonly used as an electrode active material for electric double-layer capacitors. This is a method of manufacturing activated carbon for electric double-layer capacitors. A carbon material that can be easily graphitized is used, and the starting material is fired in an atmosphere of oxidizing gas to produce the carbon material. Then, the particle size of the carbon material is adjusted, and then activated carbon is manufactured through an activation process.

As a related prior document, there is Korean Laid-Open Patent Publication No. 10-2016-0039537 (published on April 11, 2016), which describes a sheet electrode for an electric double layer capacitor and a method of manufacturing the same.

An object of the present invention is an electric double layer capacitor comprising a granular activated carbon-carbon nanotube composite capable of improving conductivity and ESR characteristics and improving energy density by applying a granular activated carbon-carbon nanotube composite as an electrode active material Is to provide.

An electric double layer capacitor including a granular activated carbon-carbon nanotube composite according to an embodiment of the present invention for achieving the above object is a case in which an upper portion is opened and an electrolyte solution is impregnated therein; A winding element inserted into the case, disposed between a cathode and an anode, and between the cathode and anode, and having a separator electrically separating the cathode and anode; And a sealing rubber bonded to the upper side of the case to seal the inside of the case, wherein the active material of each of the negative electrode and the positive electrode includes a granular activated carbon-carbon nanotube composite having an average particle diameter of 10 to 50 μm. It is characterized by being used.

The active material of each of the negative and positive electrodes is the granular activated carbon-carbon nanotube composite: 60 to 90% by weight; 1 to 15% by weight of a conductive material; And 1 to 10% by weight of a binder; it is preferable to include.

Here, the granular activated carbon-carbon nanotube composite includes activated carbon and carbon nanotubes, and the carbon nanotubes are more preferably added in an amount of 1 to 10% by weight of the total weight of the granular activated carbon-carbon nanotube composite.

The carbon nanotubes have an average diameter of 5 to 30 nm and an average length of 10 to 40 μm.

In addition, in the granular activated carbon-carbon nanotube composite, carbon nanotubes are bonded to primary particles made of activated carbon having an average particle diameter of 1 to 10 μm to form secondary particles having an average particle diameter of 10 to 50 μm.

The negative electrode includes a negative electrode current collector and a negative electrode active material layer formed on the negative electrode current collector, the positive electrode includes a positive electrode current collector and a positive electrode active material layer formed on the positive electrode current collector, and each of the negative electrode and the positive electrode active material layer It is preferable to use the granular activated carbon-carbon nanotube composite.

The electric double layer capacitor including the granular activated carbon-carbon nanotube composite according to the present invention can secure uniform dispersibility by applying the granular activated carbon-carbon nanotube as an electrode active material, and secure excellent conductive properties. Can improve ESR characteristics.

In addition, the electric double layer capacitor including the granular activated carbon-carbon nanotube composite according to the present invention is applied to the granular activated carbon-carbon nanotube composite as an electrode active material to improve the tap density of the powder and the carbon nanotubes. As an applied effect, it is possible to improve the electrode density while reducing the use of the conductive material, so that the energy density can be improved accordingly.

1 is a front view showing an electric double layer capacitor including a granular activated carbon-carbon nanotube composite according to an embodiment of the present invention.
Figure 2 is an exploded perspective view showing an enlarged winding element of Figure 1;
3 is a cross-sectional view taken along line Ⅲ-Ⅲ' of FIG. 2;
4 is a graph showing a result of measuring a change in capacity of an electric double layer capacitor manufactured according to Examples 1 to 2 and Comparative Examples 1 to 2;
5 is a graph showing a result of measuring a change in resistance for an electric double layer capacitor manufactured according to Examples 1 to 2 and Comparative Examples 1 to 2;

Advantages and features of the present invention, and a method of achieving them will become apparent with reference to the embodiments described below in detail together with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but will be implemented in a variety of different forms, only this embodiment is intended to complete the disclosure of the present invention, and the general knowledge in the technical field to which the present invention pertains. It is provided to completely inform the scope of the invention to those who have it, and the invention is only defined by the scope of the claims. The same reference numerals refer to the same elements throughout the specification.

Hereinafter, an electric double layer capacitor including a granular activated carbon-carbon nanotube composite according to a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings.

1 is a front view showing an electric double layer capacitor including a granular activated carbon-carbon nanotube composite according to an exemplary embodiment of the present invention, and FIG. 2 is an exploded perspective view showing an enlarged winding element of FIG. 1.

1 and 2, the electric double layer capacitor 100 including a granular activated carbon-carbon nanotube composite according to an embodiment of the present invention includes a case 110, a winding element 120, and a sealing rubber 130. Includes. In addition, the electric double layer capacitor 100 including the granular activated carbon-carbon nanotube composite according to an embodiment of the present invention may further include a negative external terminal 142 and a positive external terminal 144.

The upper part of the case 110 is opened, and an electrolyte solution is impregnated therein. In this case, the case 110 may have a cylindrical shape in which the upper side is opened, or may be designed in a rectangular shape such as a rectangular parallelepiped or a hexagonal column. Stainless steel may be used as the material of the case 110, but is not limited thereto.

The winding element 120 is inserted into the case 110. The winding element 120 may be of a cylindrical type, but is not limited thereto. That is, the winding element 120 may be applied in various forms such as a laminate type and a coin type. Therefore, the winding element 120 is not particularly limited in shape either.

This winding element 120 has a cathode 122, an anode 124, and a separator 126. At this time, the winding element 120 may be manufactured by winding the cathode 124, the separator 126, and the anode 124 with a winder to form a roll, and then attaching an adhesive tape or the like around the roll.

A pair of negative external terminals 142 and positive external terminals 144 are respectively negative (122)? It is connected to the anode 124. As a material of the negative external terminal 142 and the positive external terminal 144, a material such as a metal having excellent electrical conductivity such as nickel (Ni), copper (Cu), aluminum (Al), or an alloy containing them may be used. have.

The negative external terminal 142 and the positive external terminal 144 are connected to the outside through a sealing rubber 130. At this time, the cathode 122, the anode 124, and the separator 126 enclosed in the case 110 are impregnated with the electrolyte.

The sealing rubber 130 is coupled to the upper side of the case 110 to seal the inside of the case 110. The sealing rubber 130 is coupled to the negative external terminal 142 and the positive external terminal 144 in a form of fitting to prevent leakage of the electrolyte inside the case 110 to seal the case 110.

FIG. 3 is a cross-sectional view taken along line III-III' of FIG. 2, and will be described in connection with FIG. 2.

As shown in FIGS. 2 and 3, the negative electrode 122 includes a negative electrode current collector 122a and negative electrode material layers 122b and 122c formed on the negative electrode current collector 122a. In addition, the positive electrode 124 includes a positive electrode current collector 124a and positive electrode material layers 124b and 124c formed on the positive electrode current collector 124a.

3 shows that the negative electrode material layers 122b and 122c and the positive electrode material layers 124b and 124c are respectively disposed on both surfaces of the negative electrode current collector 122a and the positive electrode current collector 124a, but are limited thereto. It is not.

Here, each of the negative electrode 122 and the positive electrode 124 forms an electrode slurry by mixing an active material including a granular activated carbon-carbon nanotube composite, a conductive material, and a binder together with a solvent using a mixer to form an electrode slurry. The electrode slurry is applied thinly to the negative electrode and positive electrode current collectors 122a, 124a using a coating equipment such as a comma coater, and then convectively dried to evaporate the solvent to adhere to the positive electrode and negative electrode current collectors 122a, 124a. Can be formed.

At this time, in the present invention, the active material used for the negative electrode material layers 122b and 122c and the positive electrode material layers 124b and 124c is a granular activated carbon-carbon nanotube composite. This granular activated carbon-carbon nanotube composite is prepared by mixing activated carbon powder and a carbon nanotube dispersion using a stirring tank and then drying using a spray drying method to obtain a granular powder.

Here, it is preferable to use activated carbon powder having an average particle diameter of 1 to 10 μm.

In addition, the granular activated carbon-carbon nanotube composite includes activated carbon and carbon nanotubes, but the carbon nanotubes are more preferably added in an amount of 1 to 10% by weight of the total weight of the granular activated carbon-carbon nanotube composite. When the amount of carbon nanotubes added is less than 1% by weight of the total weight of the granular activated carbon-carbon nanotube composite, it is difficult to properly exhibit the effect of improving conductivity. Conversely, when the amount of carbon nanotubes is added in a large amount exceeding 10% by weight of the total weight of the granular activated carbon-carbon nanotube composite, it is not economical because only the manufacturing cost can be increased without further increase in effect.

In addition, it is preferable to use a granular activated carbon-carbon nanotube composite having an average particle diameter of 10 to 50 μm. When the average particle diameter of the granular activated carbon-carbon nanotube composite is less than 10 μm, it is difficult to properly exhibit the energy density improvement effect. Conversely, when the average particle diameter of the granular activated carbon-carbon nanotube composite exceeds 50 μm, immiscibility may occur.

Here, the active material of each of the negative electrode and the positive electrode is more preferably a granular activated carbon-carbon nanotube composite: 60 to 90% by weight, 1 to 15% by weight of a conductive material, and 1 to 10% by weight of a binder.

At this time, it is more preferable to use carbon nanotubes having an average diameter of 5 to 30 nm and an average length of 10 to 40 μm.

As the activated carbon added to the granular activated carbon-carbon nanotube composite, at least one selected from wood powder, palm tree, coconut, petroleum pitch, and phenol may be used.

The conductive material may include conductive powder such as Super-P, Ketjen black, acetylene black, carbon black, graphite, etc., but is not limited thereto.

It is preferable to use a different type of binder as the binder. Specifically, it is preferable to use the binder added together with polytetrafluoroethylene (PTFE), rubber-based resin, and acrylic resin. In addition, as a secondary binder of the binder, a cellulose resin, a fluorine resin including polyvinylidene fluoride (PVDF), a thermoplastic resin including polyimide, polyamide, polyethylene and polypropylene, and a carboxymethylcellulose (CMC) And it may further include one or more selected from a mixture thereof.

The separator 126 prevents the cathode 122 and the anode 124 from physically contacting each other. In addition, the separator 126 is preferably porous, and a conductive path between the cathode 122 and the anode 124 is formed by maintaining the electrolyte in the pores. The material of the separator 126 is not particularly limited. For example, the material of the separator 126 may be selected from porous cellulose, polypropylene, polyethylene, and fluorine-based resin.

In addition, a conductive adhesive and a conductive coating layer may be further formed on the surfaces of the negative electrode current collector 122a and the positive electrode current collector 124a made of metal foil, respectively, as necessary.

The metal foil used for the anode and cathode current collectors 122a and 124a may be made of a metal exhibiting conductivity, but is not necessarily limited thereto, and aluminum or copper is preferred. Dimensions such as the size and thickness of the metal foil are not particularly limited.

The electric double layer capacitor including the granular activated carbon-carbon nanotube composite according to the above-described embodiment of the present invention can secure uniform dispersibility by applying the granular activated carbon-carbon nanotube as an electrode active material. Conductive properties can be secured, and ESR properties can be improved.

In addition, the electric double layer capacitor including the granular activated carbon-carbon nanotube composite according to an embodiment of the present invention uses the granular activated carbon-carbon nanotube composite in the form of granules as an electrode active material to improve the tap density and carbon The application effect of the nanotubes can improve the electrode density while reducing the use of the conductive material, and thus the energy density can be improved.

Example

Hereinafter, the configuration and operation of the present invention will be described in more detail through preferred embodiments and comparative examples of the present invention. However, this is presented as a preferred example of the present invention and cannot be construed as limiting the present invention in any sense.

Contents not described herein can be sufficiently technically inferred by those skilled in the art, and thus description thereof will be omitted.

1. Active material manufacturing

Preparation of granular activated carbon-carbon nanotube composite

Carbon nanotubes having a diameter of 10 nm and a length of 25 μm were placed in an activated carbon powder having an average particle diameter of 5 μm in a stirring tank together with distilled water, followed by stirring for 2 hours. At this time, a small amount of an organic dispersant was added to improve dispersibility.

Next, the agitated slurry was finally mixed with activated carbon and carbon nanotubes using a milling facility, and then granulated by spray drying.

Next, heat treatment was performed at 700° C. in a nitrogen atmosphere to prepare a granular activated carbon-carbon nanotube composite having an average particle diameter of 30 μm.

2. Electric double layer capacitor manufacturing

Example 1

Electrode manufacturing

After preparing an electrode slurry by mixing and stirring a granular activated carbon-carbon nanotube composite having an average particle diameter of 30 μm, a conductive material, and a binder in pure water, coating and drying the aluminum foil current collector using a comma coater, the electrode slurry and In order to improve the contact characteristics of the current collector, an electrode was manufactured by performing a roll pressing process.

At this time, it was composed of 84 wt% of granular activated carbon-carbon nanotube composite, 10 wt% of conductive material and 6 wt% of binder, and Super-P as a conductive material, and polytetrafluoroethylene, methyl cellulose and styrene butyene rubber as a binder. A mixture of was used.

Cell manufacturing

After attaching the positive and negative external terminals to each of the positive and negative electrodes, a separator was disposed between the positive and negative electrodes, and wound in a roll shape to manufacture a winding element. Next, the winding element was dried in an oven at 150° C. for 24 hours.

Next, after the dried winding element was inserted into the cylindrical case, 1M tetraethylammonium tetrafluoroborate/acetonite was impregnated using a solvent (TEABF ₄ /ACN).

Next, after inserting the sealing rubber into the negative external terminal and the positive external terminal, the case was curled to prepare a cell having a size of 10 × 25 mm.

Example 2

When preparing the electrode, a cell was manufactured in the same manner as in Example 1, except that a composition of 88 wt% of a granular activated carbon-carbon nanotube composite, 6 wt% of a conductive material, and 6 wt% of a binder was used.

Comparative Example 1

When manufacturing the electrode, a cell was manufactured in the same manner as in Example 1, except that carbon nanotubes were not included and activated carbon having an average particle diameter of 15 μm was used instead of granular form.

Comparative Example 2

When manufacturing the electrode, a cell was manufactured in the same manner as in Example 1, except that carbon nanotubes were not included and granular activated carbon having an average particle diameter of 30 μm was used.

3. Evaluation method

Table 1 shows the results of measuring capacitance and internal resistance as initial characteristics of the electric double layer capacitors manufactured according to Examples 1 to 2 and Comparative Examples 1 to 2. At this time, the capacitance was calculated from the slope of the discharge curve when the electric double layer capacitor was charged from 100mA to 2.7V using a charge/discharge tester, maintained at a constant voltage for 30 minutes, and then discharged from 100mA to 0.1V. Here, the internal resistance was measured at 1 kHz AC resistance.

[Table 1]

As shown in Table 1, it can be seen that the electric double layer capacitors manufactured according to Examples 1 to 2 have a density of 0.58 to 0.59 g/cc and a capacity of 10.5 F or more, and an ESR of 18.5 mΩ or less.

On the other hand, the electric double layer capacitor manufactured according to Comparative Example 1 had a considerably low density and capacity, and the ESR was 19.6 mΩ, indicating poor conductivity.

In addition, the electric double layer capacitor manufactured according to Comparative Example 2 had a density similar to that of Example 1, but the capacity was measured as low as 10.2F, and in particular, the ESR was measured as 22.4mΩ, indicating very poor conductivity.

4. High temperature load test

4 is a graph showing the result of measuring the capacity change for the electric double layer capacitor manufactured according to Examples 1 to 2 and Comparative Examples 1 to 2, and FIG. 5 is a graph according to Examples 1 to 2 and Comparative Examples 1 to 2 It is a graph showing the result of measuring the resistance change for the manufactured electric double layer capacitor. At this time, it shows the results of performing a high-temperature test for 1,000 hours at 2.7V 65°C for the electric double layer capacitors manufactured according to Examples 1 to 2 and Comparative Examples 1 to 2.

4 and 5, the electric double charge capacitor manufactured according to Examples 1 to 2 changed the resistance and capacity at a high temperature (65°C) compared to the electric double layer capacitor manufactured according to Comparative Examples 1 to 2 You can see that is small.

As can be seen on the basis of the above experimental results, it is possible to significantly reduce the rate of change of resistance and capacity when applying the granular activated carbon-carbon nanotube composite as an electrode active material, such as the electric double layer capacitor manufactured according to Examples 1 to 2. Confirmed.

In the above, the embodiments of the present invention have been described mainly, but various changes or modifications can be made at the level of those of ordinary skill in the art to which the present invention pertains. Such changes and modifications can be said to belong to the present invention as long as they do not depart from the scope of the technical idea provided by the present invention. Therefore, the scope of the present invention should be determined by the claims set forth below.

100: electric double layer capacitor 110: case
120: winding element 122: cathode
124: anode 126: separator
130: sealing rubber 142: negative external terminal
144: positive external terminal

Claims (6)

A case in which the upper part is opened and the electrolyte is impregnated therein;
A winding element inserted into the case, disposed between a cathode and an anode, and between the cathode and anode, and having a separator electrically separating the cathode and anode; And
As an electric double layer capacitor comprising; a sealing rubber coupled to the upper side of the case to seal the inside of the case,
As the active material of each of the negative electrode and the positive electrode, a granular activated carbon-carbon nanotube composite having an average particle diameter of 10 to 50 μm is used,
The active material of each of the negative and positive electrodes is the granular activated carbon-carbon nanotube composite: 60 to 90% by weight; 1 to 15% by weight of a conductive material; And 1 to 10% by weight of a binder; and,
The granular activated carbon-carbon nanotube composite includes activated carbon and carbon nanotubes, wherein the carbon nanotubes are added in an amount of 1 to 10% by weight of the total weight of the granular activated carbon-carbon nanotube composite,
The electric double layer capacitor has a density of 0.58 to 0.59 g/cc, a capacity of 10.7 to 11.1 F, and an ESR of 16.3 to 18.1 mΩ. An electric double layer capacitor comprising a granular activated carbon-carbon nanotube composite.
delete delete The method of claim 1,
The carbon nanotubes are
Electric double-layer capacitor comprising a granular activated carbon-carbon nanotube composite, characterized in that it has an average diameter of 5 ~ 30nm and an average length of 10 ~ 40㎛.
The method of claim 1,
The granular activated carbon-carbon nanotube composite
A granular activated carbon-carbon nanotube composite characterized in that carbon nanotubes are bonded to primary particles made of activated carbon having an average particle diameter of 1 to 10 μm to form secondary particles having an average particle diameter of 10 to 50 μm. Electric double layer capacitor containing.
The method of claim 1,
The negative electrode includes a negative electrode current collector and a negative electrode active material layer formed on the negative electrode current collector, and the positive electrode includes a positive electrode current collector and a positive electrode active material layer formed on the positive electrode current collector,
Each of the anode and cathode active material layers is an electric double layer capacitor comprising a granular activated carbon-carbon nanotube composite, characterized in that the granular activated carbon-carbon nanotube composite is used.

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