Electrode for multilayer capacitor and manufacturing method of the same

Abstract

To provide a long-life, high-performance, and practical electrode for multilayer capacitor.SOLUTION: In an electrode for multilayer capacitor comprising multilayer carbon nanotubes vertically oriented on both surfaces of a Cu substrate and in a manufacturing method of the same, Fe fine particles are coded on both surfaces of a Cu substrate, the Cu substrate is provided in a thermal CVD device in an upright state in the gas supply direction, and in the thermal CVD device, multilayer carbon nanotubes vertically oriented on both surfaces of a conductive metal substrate are formed at a temperature of 750 to 850°C in a mist atmosphere generated by atomizing an Fe / ethanol mixed liquid.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an electrode for a multilayer capacitor and a method for manufacturing the same. [Background technology]

[0002] Multilayer capacitors are attracting attention as devices that can be charged and discharged rapidly, have little deterioration, and have a long life. Currently, large-capacity capacitors are being developed (for electric vehicles, lifting equipment, automated factories), and small capacitors are also needed for applications such as home appliances, mobile phones, and mobile communications.

[0003] Conventional activated carbon is used as the electrode for multilayer capacitors. However, when powdered activated carbon is formed into an electrode, a conductive adhesive is required. This adhesive can deteriorate due to impurities and dirt on the surface of the adhesive or activated carbon, which has led to a problem of shortening the lifespan of the electrode. Therefore, there is a demand for the development of a long-life, high-performance, and practical multilayer capacitor electrode that can replace activated carbon electrodes. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2012-136362 [Patent Document 2] Patent Publication No. 2005-286247 [Patent Document 3] Re-table 2004 / 084244 [Non-patent literature]

[0005] [Non-Patent Document 1] Jianhui Zhang, Wei Li, Tetsuo Soga, Takashi Jimbo and Takayoshi Tanji, “Synthesis of High-Density Vertically Aligned Carbon Nanotubes Using Ultrasonic Nebulizer”, Materials Sciences and Applications, Volume 2012, 3, 213-217 Summary of the Invention [Problem to be solved by the invention]

[0006] According to the inventor's research, multi-walled carbon nanotubes (MWNTs), which grow vertically aligned, are a material in which six-membered ring networks (graphene sheets) made of carbon are arranged in the form of multiple coaxial tubes. They have high density, high heat resistance, electrical conductivity, high acid resistance and chemical stability. Furthermore, because they have a fibrous structure, they are electrically conductive, do not require adhesives, have few impurities on their surface, and have an extremely large specific surface area. There are large amounts of "gaps" between the nanotubes, which makes it possible to store large amounts of electrons and protons therein. These make them ideal for use as electrodes for multilayer capacitors, and multi-walled carbon nanotubes (MWNTs) are expected to be used in applications such as multilayer capacitors.

[0007] However, conventional multi-walled carbon nanotube (MWNTs) synthesis methods have not been able to confirm sufficient performance as a multilayer capacitor electrode due to the presence of substances such as impurities and dirt on the adhesive or activated carbon surface. As a result of trial and error research, the inventors have developed a synthesis method for vertically aligned multi-walled carbon nanotubes (MWNTs) made of pure carbon containing no impurities, thereby expanding the range of applications for multilayer capacitor electrodes. [Means for solving the problem]

[0008] The present invention proposes an electrode for a multilayer capacitor, the electrode being a conductive metal substrate having vertically oriented multi-layer carbon nanotubes on both sides thereof.

[0009] Furthermore, the present invention proposes a method for manufacturing an electrode for a multilayer capacitor, in which iron-based metal fine particles are coated on both sides of a conductive metal substrate, the conductive metal substrate is arranged upright in a thermal CVD apparatus in the gas supply direction, and multi-layered carbon nanotubes oriented vertically are provided on both sides of the conductive metal substrate at a temperature of 600 to 900°C in a mist atmosphere in which an iron-based metal / alcohol mixed liquid is atomized in the thermal CVD apparatus.

[0010] Here, examples of the conductive metal substrate include substrates made of Cu, aluminum, titanium, and the like.

[0011] Examples of iron-based metals include Fe, Co, and Ni, with a representative example being Fe. A representative example of an iron-based metal / alcohol mixed liquid is an Fe / ethanol mixed liquid.

[0012] Furthermore, the temperature range is 600 to 900°C, and preferably 750 to 850°C. Effect of the Invention

[0013] That is, according to the present invention, a large amount of electrons can be stored in the gaps between the multi-walled carbon nanotubes, making it possible to provide a long-life, high-performance electrode for a multilayer capacitor. [Brief description of the drawings]

[0014] [Figure 1] Multilayer capacitor diagram [Diagram 2] Schematic diagram of a thermal CVD apparatus equipped with a nebulizer [Diagram 3] SEM images of synthesized vertically aligned multi-walled carbon nanotubes (MWNTs) [Figure 4] SEM images of vertically aligned multi-walled carbon nanotubes (MWNTs) synthesized at different temperatures [Diagram 5] TEM images of differently synthesized vertically aligned multi-walled carbon nanotubes (MWNTs) [Figure 6] EDS spectra of synthesized vertically aligned multi-walled carbon nanotubes (MWNTs) [Figure 7] Diagram of the manufacturing method of multilayer capacitors DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] An electrode for a multilayer capacitor having multi-walled carbon nanotubes aligned vertically on both sides of a Cu substrate and a method for manufacturing the electrode include coating both sides of a Cu substrate with Fe fine particles, placing the Cu substrate upright in a thermal CVD apparatus in the gas supply direction, and providing multi-walled carbon nanotubes aligned vertically on both sides of a conductive metal substrate at a temperature of 750 to 850°C in a mist atmosphere of atomized Fe / ethanol mixed liquid within the thermal CVD apparatus. EXAMPLES

[0016] The present invention will be described below based on the illustrated embodiments. Fig. 1 is a schematic diagram of a multilayer capacitor incorporating electrodes according to the present invention. The capacitor is made up of four Cu substrates (1), and heat-resistant insulating resin (3) is inserted into the Cu substrates (1) on which CNTs were placed, and vertically oriented multi-walled carbon nanotubes (2) are synthesized on the Cu substrates (1) using a thermal CVD device, and finally wired (12).

[0017] The manufacturing process of the multilayer capacitor will be described with reference to FIG. Steps shown in Figure 7A Four Cu substrates (1) are being cleaned. <Step shown in Figure 7B> Four Cu substrates (1) are coated on both sides with Fe particles (5) by vacuum deposition. <Step shown in FIG. 7C> The four Cu substrates (1) are placed in a thermal CVD apparatus, and multi-walled carbon nanotubes (MWNTs) (2) are vertically aligned on both sides of the four Cu substrates (1) to form stacked capacitor electrodes. <Step shown in Figure 7D> The two Cu(1) substrates on the right side, the two Cu(1) substrates on the left side, and the heat-resistant insulating resin (3) are arranged separately to assemble the multilayer capacitor, and the solder terminals (4) are attached. <Step shown in FIG. 7E> The multilayer capacitor is wired (12).

[0018] Method for manufacturing electrodes for multilayer capacitors 2 is a schematic diagram of an apparatus used in the method of the present invention. The method of the present invention will be described with reference to the apparatus of FIG. The thermal CVD apparatus has three main parts: an electric furnace (6), a nebulizer device (9), and a nitrogen gas canister (8). In Fig. 2, the electric furnace (6), the nebulizer device (9), and the nitrogen gas canister (8) are arranged in that order from left to right. However, the apparatus used in the method of the present invention is not limited to this.

[0019] Next, a manufacturing procedure using the apparatus shown in FIG. 2 will be described. (1) Using an ultrasonic cleaning device, the Cu substrate (1) is first washed in order with acetone, a methanol solution, and ultrapure water, and then the remaining ultrapure water on the Cu substrate (1) is removed with a nitrogen gun.

[0020] (2) Place the cleaned Cu substrate (1) in the electric furnace (6) of the thermal CVD equipment, open the nitrogen valve (7), set the nitrogen flow rate to 0.1 L / min, and allow it to flow for about 10 minutes. Turn on the electric furnace (6) of the thermal CVD equipment and allow it to heat for about 600 to 800 o Heat to C, wait another 10 minutes, and then turn on the nebulizer device (9).

[0021] The nebulizer device (9) (1.65 MHz, Atom Medical Corp., Model 303) described in (3)(2) is a key device of the thermal CVD device in the present invention, which can atomize the Fe / ethanol mixed liquid and deliver the raw material gas to the surface of the Cu substrate (1) in the thermal CVD device via nitrogen gas for synthesis.

[0022] (4) The proportions of the Fe / ethanol mixed liquid described in (1) are 10 wt% and 100 ml, respectively.

[0023] (5) The reaction time was about 1 hour. After the experiment was completed, the power to the electric furnace (6) of the thermal CVD apparatus was turned off, and the temperature of the electric furnace (6) was allowed to drop to room temperature before removing the Cu substrate (2).

[0024] (6) A heat-resistant insulating resin material (4) is applied or inserted onto the Al substrate (1).

[0025] FIG. 3 shows a typical SEM image of high-density vertically aligned multi-walled carbon nanotubes (MWNTs) synthesized at a synthesis temperature of about 800° C., where high-density nanotubes with lengths of 10 μm are observed.

[0026] As shown in Fig. 4(a), the SEM image shows that the nanotubes can form a dense vertical state with a length of about 3 μm at a synthesis temperature of 750°C. The SEM image in Fig. 4(b) shows that the nanotubes can form a dense vertical state with a length of about 10 μm at a synthesis temperature of 850°C.

[0027] As shown in Figure 5(a) and (b), it can be clearly observed that the carbon nanotubes have straight morphology, smooth walls, closed ends, and clean surfaces. The outer diameter of the carbon nanotubes ranges from 10 to 30 nm, and the inner diameter of the carbon nanotubes is usually about 2 to 5 nm.

[0028] Figure 6 shows the EDS spectrum showing three strong peaks representing Cu, Fe, and C. This suggests that the growth of vertically aligned multi-walled carbon nanotubes (MWNTs) originates from Fe or Fe carbide particles on the Cu substrate. [Industrial Applicability]

[0029] The present invention can provide a practical multilayer capacitor electrode that has a long life and high performance. [Explanation of symbols]

[0030] 1………………Cu substrate 2. Vertically aligned multi-walled carbon nanotubes (MWNTs) 3. Heat-resistant insulating resin 4………………Solder terminal 5………………Fe fine particles 6………………Electric furnace 7………………Nitrogen valve 8………………Nitrogen gas canister 9. Nebulizer device 10... Gas supply port 11………………Exhaust port 12………………Wiring

Claims

1. An electrode for a multilayer capacitor, in which multi-layer carbon nanotubes are vertically oriented on both sides of a conductive metal substrate.

2. A manufacturing method for electrodes for multilayer capacitors in which iron-based metal particles are coated on both sides of a conductive metal substrate, the conductive metal substrate is placed upright in a thermal CVD apparatus in the gas supply direction, and multi-layer carbon nanotubes are provided that are vertically oriented on both sides of the conductive metal substrate at a temperature of 600-900°C in a mist atmosphere of an iron-based metal / alcohol mixture liquid.

3. 3. The method according to claim 2, wherein the iron-based metal is Fe, and the iron-based metal / alcohol mixed liquid is an Fe / ethanol mixed liquid.

4. The method according to claim 2, wherein the temperature is in the range of 750 to 850°C.

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