JP2011171400A - Electrode member using carbon nanotube, electric double layer capacitor using electrode member, and method of manufacturing electrode member - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrode member using a carbon nanotube of large capacitance and long life. <P>SOLUTION: Relating to an electrode member 4, at least a double-wall carbon nanotube and a multi-wall carbon nanotube are arranged in multiple numbers on the surface of a manufacturing electrode 11 comprising a silicon substrate. On the surface of the manufacturing electrode 11, a catalyst layer 13 and a film-forming layer 12 comprising aluminum oxide are sequentially formed. Then, on the surface of the catalyst layer 13, a number of double-wall carbon nanotubes and multi-wall carbon nanotubes (14) are vertically arranged. A rate of the double-wall carbon nanotube to the entire carbon nanotubes comes into the range of 1/3 to 2/3. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an electrode member using carbon nanotubes, an electric double layer capacitor using the electrode member, and a method for manufacturing the electrode member.

  Conventionally, in an electric double layer capacitor, a separator such as a nonwoven fabric made of polypropylene is sandwiched between a pair of polarizable electrodes in which a polarizable electrode layer mainly composed of activated carbon is formed on a current collector, and the element An element obtained by impregnating an electrode layer with an electrolytic solution was housed in a metal container, and the metal container was sealed with a sealing plate and a gasket.

  However, activated carbon has a large specific surface area, and generally has low electrical conductivity, and the activated carbon alone increases the internal resistance of the polarizable electrode, so that a large current cannot be taken out. Attempts have been made to increase the capacity by increasing the electrical conductivity by containing carbon nanotube groups in the electrode.

  For example, for carbon nanotubes, single-walled (single-walled carbon nanotubes: SWNT), multi-walled (double-walled carbon nanotubes: DWNT) and multi-walled (multi-walled carbon nanotubes: MWNT) are known. A capacitor having a large capacity by using carbon nanotubes is known (for example, see Patent Document 1).

WO2006 / 088004

  However, according to the configuration of the capacitor, since a long single carbon nanotube can be generated, there is an advantage that a large capacity can be realized, but there is a problem that durability is inferior and life is short.

  As for the double carbon nanotubes, the number density per unit area can be increased, so that there is an advantage that a large capacity can be realized and the crystallinity is high and the life is long. There is a problem that the surface area is small compared to the above.

  Furthermore, the multi-carbon nanotube has a problem that although the surface area per one is high, the number density per unit area is low and the capacity is inferior to that of the double carbon nanotube.

  Accordingly, an object of the present invention is to provide an electrode member using carbon nanotubes capable of increasing the capacity and extending the life, an electric double layer capacitor using the electrode member, and a method for manufacturing the electrode member.

In order to solve the above-mentioned problems, an electrode member using carbon nanotubes according to claim 1 of the present invention has a large number of at least double wall carbon nanotubes and multiwall carbon nanotubes arranged vertically on the surface of the electrode substrate. An electrode member,
The ratio of the double wall carbon nanotubes to the total carbon nanotubes is in the range of 1/3 to 2/3.

An electrode member using carbon nanotubes according to claim 2 is an electrode member in which a large number of at least double wall carbon nanotubes and multiwall carbon nanotubes are arranged vertically on the surface of the electrode substrate,
At least an aluminum oxide layer and a catalyst layer are sequentially disposed on the surface of the electrode substrate,
Further, a large number of the double-walled carbon nanotubes and multi-walled carbon nanotubes are arranged vertically on the surface of the catalyst layer so that the ratio of the double-walled carbon nanotubes to the total carbon nanotubes is in the range of 1/3 to 2/3. It is a thing.

Further, in the electrode member using the carbon nanotube according to claim 3, the formation density of the multi-wall carbon nanotube in the electrode member according to claim 1 or 2 is set to 10 ¹⁰ to 10 ¹³ pieces / cm ² . Is.

  According to a fourth aspect of the present invention, there is provided an electric double layer capacitor in which an electrode member using the carbon nanotube according to any one of the first to third aspects is disposed in a container so that the carbon nanotubes face each other. In addition, a separator is disposed between the two electrode members and an electrolyte is filled therein.

Further, the method for producing an electrode member according to claim 5 of the present invention is a method for producing an electrode member in which a large number of double wall carbon nanotubes and multiwall carbon nanotubes are arranged,
After at least an aluminum oxide layer and a catalyst layer are sequentially formed on the surface of the production substrate, a large number of the double wall carbon nanotubes and multi-wall carbon nanotubes are vertically formed on the surface of the catalyst layer, and the double wall for the carbon nanotubes. Formed so that the proportion of carbon nanotubes is in the range of 1/3 to 2/3,
Next, there is a method for obtaining an electrode member by transferring carbon nanotubes formed on the surface of the production substrate to an electrode substrate.

Furthermore, the manufacturing method of the electrode member using the carbon nanotube which concerns on Claim 6 is a manufacturing method of the electrode member of Claim 5, The formation density of a multi-wall carbon nanotube is ¹⁰ <10> -10 < ¹³ > piece / cm < ² >. It is a method.

  According to each of the above configurations, the double-walled carbon nanotubes and the multi-walled carbon nanotubes are formed vertically on the substrate surface, and the formation ratio of the double-walled carbon nanotubes is in the range of 1/3 to 2/3. Therefore, for example, when an electrode member is used for a capacitor, its capacity and life can be increased.

It is sectional drawing which shows the basic composition of the electrode member and electric double layer capacitor which concern on embodiment of this invention. It is sectional drawing which shows schematic structure of the electrical double layer capacitor which concerns on embodiment of this invention. It is principal part sectional drawing explaining the manufacturing method of the electrical double layer capacitor which concerns on embodiment of this invention.

Hereinafter, an electrode member using carbon nanotubes according to an embodiment of the present invention, an electric double layer capacitor using the electrode member, and a method for manufacturing the electrode member will be described.
First, an electric double layer capacitor using an electrode member having carbon nanotubes will be briefly described.

  This electric double layer capacitor has a pair of electrode members (also referred to as power storage elements) made of a current collector and a polarizable electrode disposed in a container, a separator disposed between the pair of electrode members, and the container. It is comprised from the electrolyte solution (a solid electrolyte may be sufficient) as electrolyte filled.

  More specifically, as shown in FIG. 1, a large number of carbon nanotubes 3 that are polarizable electrodes are formed by thermal CVD on the surface (one side) of an electrode substrate 2 that is a current collector in a metal container 1. A pair of electrode members 4 formed vertically by the method (so-called vertically aligned) are disposed with the carbon nanotubes 3 facing each other with a separator 5 interposed therebetween, and an electrolyte solution in the container 1. In addition, at least double-wall carbon nanotubes and multi-wall carbon nanotubes are arranged (formed) as carbon nanotubes, and the ratio (formation ratio) of the double-wall carbon nanotubes is the entire carbon nanotube (of course) Or may contain single wall carbon nanotubes) It is to be in the range of 3 to 2/3.

In addition, although the basic structure of the electric double layer capacitor is shown in FIG. 1, normally, as shown in FIG. 2, a structure in which the basic structure is arranged in multiple layers is used.
In this case, an internal electrode member 4 (4B) in which a large number of carbon nanotubes 3 are arranged on the upper and lower surfaces is arranged in layers between the upper and lower end electrode members 4 (4A, 4A) via the separator 5. In addition, the container 1 is filled with the electrolytic solution.

Next, the manufacturing method of the electrode member 4 using the carbon nanotube 3 is demonstrated.
As shown in FIG. 3, first, the film formation layer 12 is formed on the surface of the production substrate 11, then the catalyst layer 13 is formed on the surface of the film formation layer 12, and then the surface of the catalyst layer 13 is formed. In this method, carbon nanotubes (carbon nanotube group) 14 are formed vertically. As described above, the carbon nanotube 14 is composed of at least a double-wall carbon nanotube and a multi-wall carbon nanotube, and the formation ratio of the double-wall carbon nanotube is an all-carbon nanotube (the entire carbon nanotube is a single-wall carbon nanotube. May be included in the range of 1/3 to 2/3.

A silicon substrate (Si substrate) is used as the production substrate 11, aluminum oxide (Al ₂ O ₃ ) is used as the film formation layer 12, and a metal is used as the catalyst layer 13. , Iron (Fe), cobalt (Co), nickel (Ni), molybdenum (Mo), or any combination thereof. The manufacturing substrate 11 may not be a silicon substrate, and may be a silicon foil, for example. In short, any material can be used as long as it can withstand a temperature of 600 to 1000 ° C. during CVD.

Furthermore, the thickness of the film formation layer 12 is in the range of 5 to 50 nm, and the thickness of the catalyst layer 13 is in the range of 1 to 5 nm.
The density of the double wall carbon nanotube is set to be in the range of 0.01 to 0.2 g / cc.

Here, the reason why the film formation layer 12 of aluminum oxide (Al ₂ O ₃ ) is formed on the surface of the manufacturing substrate 11 which is a silicon substrate will be described.
In general, aluminum oxide (Al ₂ O ₃ ) has an α-alumina structure at a high temperature and a γ-alumina structure when heated at a low temperature (about 600 to 1000 ° C.). This γ-alumina has a spinel structure (square lattice). ), And there are defects in the structure. Therefore, when the catalyst particles are heated, if there is a defect, the catalyst particles are easily selectively fixed at the position, and aggregation of the catalyst particles is prevented, so that carbon nanotubes having an appropriate thickness can be generated.

Specifically, aluminum oxide (Al ₂ O ₃ ) has nano-sized bores (cavities), and iron, which is a catalyst that has been granulated during heating, does not get stuck in the bore and cause aggregation of particles. Therefore, coarsening of the catalyst particles is prevented. That is, it is possible to form catalyst particles having an appropriate size. Therefore, the aluminum oxide layer is provided in order to form carbon nanotubes having an appropriate thickness.

  Further, the thickness of the aluminum oxide layer will be described. When the thickness is smaller than 5 nm, since the depth of the bore is shallow, the particles overflow from the bore and adhere to and aggregate with adjacent particles. On the contrary, when the film thickness of aluminum oxide is thicker than 50 nm, the bore is too deep and the iron particles sink into the back, and the source gas such as ethylene and acetylene cannot reach. Therefore, the thickness of the film-forming layer 12 made of aluminum oxide is set to a thickness that does not bury the catalyst particles (for example, about 2 nm or more for iron), that is, in the range of 5 to 50 nm, preferably several tens. The range is ˜50 nm.

Here, the arrangement in the case of forming the carbon nanotube will be considered.
When the catalyst particles are aligned, an arrangement in which the density is highest (for example, a state in which the catalyst particles are positioned in a triangular lattice point) is preferable.

  By the way, in the group of carbon nanotubes, the total surface area becomes larger when partially including multi-wall carbon nanotubes than when all of them are double-wall carbon nanotubes. However, if all are multi-wall carbon nanotubes, the multi-wall carbon nanotubes have a short lifetime, so in order to include a double-wall carbon nanotube with a long lifetime and a large surface area, double-wall carbon nanotubes and multi-wall carbon nanotubes It is preferable to include carbon nanotubes. In this case, it is preferable that 1/3 to 2/3 of the triangular lattice points are double wall carbon nanotubes and the rest are multiwall carbon nanotubes.

Here, a specific method for manufacturing the electrode member will be described.
First, an aluminum oxide layer (Al ₂ O ₃ ) having a thickness of 20 nm is formed on the surface of a silicon substrate (Si) as a manufacturing substrate by vacuum deposition, and then an iron (Fe) catalyst layer is formed by vacuum deposition to 2 nm. It is formed with the thickness of

  Next, carbon nanotubes are formed perpendicularly to the surface of the catalyst layer by using a carbon gas (raw material gas) such as ethylene or acetylene by a thermal CVD method. Hydrogen gas is used to increase the activity of the catalyst.

Water is added to the carbon gas.
When water is added, if there is a part with low crystallinity on the carbon surface grown from the catalyst layer (precisely, metal particles which are catalyst particles), the part reacts with water, and as a result, the crystallinity is high. This is because things (that is, fewer defects in the graphene sheet on the tube surface) are likely to remain. When the crystallinity of the tube is high, a side reaction (decomposition reaction or the like) with the electrolytic solution is unlikely to occur, and therefore the life is extended.

Moreover, the temperature at the time of CVD is about 600-1000 degreeC, and the density | concentration of carbon gas shall be 20% or less.
Next, the production substrate is placed so that the orientation surface of the carbon nanotube faces the surface of the electrode substrate, and is pressed (pressed) at a predetermined pressure and for a predetermined time, and then the production substrate is peeled off from the carbon nanotube. As a result, the carbon nanotubes are transferred to the electrode substrate.

In addition, the structure of the said electrode member is demonstrated roughly.
That is, this electrode member is an electrode member in which a large number of at least double wall carbon nanotubes and multiwall carbon nanotubes are arranged vertically on the surface of the electrode substrate,
The ratio of the double wall carbon nanotubes to the total carbon nanotubes is in the range of 1/3 to 2/3,
Moreover, the formation density of the said multi-wall carbon nanotube shall be ¹⁰ <10> -10 < ¹³ > pieces / cm < ² >.

  By the way, when the electrode member is applied to an electric double layer capacitor, an aluminum foil having a thickness of about 50 μm is used as the electrode substrate, and the carbon nanotube is a metal foil made of aluminum, copper, nickel, stainless steel, or the like. The one transcribed into is the current collector.

  That is, after a resin paste having adhesiveness and conductivity is applied to the surface of an aluminum foil having a thickness of about 50 μm, the production substrate is placed so that the orientation surfaces of the carbon nanotubes face each other. Pressurization is performed while heating at a temperature of about 200 ° C. (so-called hot press). Then, the carbon nanotubes are transferred by peeling off the production substrate 11 from the aluminum foil.

  The configuration of the electric double layer capacitor will be schematically described. The electrode members using the carbon nanotubes described above are arranged in a container so that the carbon nanotubes face each other, and between the two electrode members. In addition, a separator is disposed and an electrolytic solution (electrolyte) is filled.

  Moreover, the electrode substrate for transferring the carbon nanotubes is not limited to the metal foil described above, and for example, a sheet-like member such as a conductive resin film or resin sheet can be used.

  For example, in the transfer to the resin film, the substrate for production is placed so that the orientation surfaces of the carbon nanotubes face each other in a state where the temperature of the resin film is heated to a range not lower than the softening temperature and not higher than the melting temperature, and predetermined Pressurize (press) the pressure and for a predetermined time. Thereafter, the temperature of the resin film is cooled to the softening temperature or lower, and the transfer is performed by peeling the production substrate from the resin film. In addition, the resin film can use what is generally marketed, for example, PET / ITO (Indium Tin Oxide) / Pd.

By the way, although the ratio of the double-walled carbon nanotubes is in the range of 1/3 to 2/3 of the entire carbon nanotubes, for example, it may be 25 to 75%.
Here, the advantage of using the double wall carbon nanotube for the electrode member will be described.

  That is, a capacitor using double-walled carbon nanotubes has a larger capacitance and a longer life compared to a capacitor using multi-walled carbon nanotubes. High performance. As described above, when the crystallinity of the tube is increased, side reaction (decomposition reaction or the like) with the electrolytic solution is less likely to occur, and thus the life is increased and the withstand voltage performance is increased. As the withstand voltage performance increases, the upper limit voltage at which operation is possible also increases.

  In other words, by making the ratio of the double-walled carbon nanotubes in the range of 1/3 to 2/3 of the entire carbon nanotubes, the single carbon nanotubes can overcome the disadvantage of low durability and short lifetime, The disadvantage that multi-carbon nanotubes have a low number density per unit area and inferior capacity can be overcome. Briefly, the double wall carbon nanotubes are formed at a ratio of 1/3 to 2/3, thereby increasing the number density per unit area (when the formation ratio is 2/3, the number density is 2 And the surface area of the carbon nanotube per area increases), the electrode member can have a higher capacity, that is, the capacity of the capacitor can be increased, and the crystallinity becomes higher, resulting in a longer life.

  In the above embodiment, a non-conductive and heat-resistant silicon substrate is used as the production substrate. For example, when a conductive metal foil (or metal plate) is used, the metal foil Since carbon nanotubes cannot be directly generated on the surface, an intermediate layer or a buffer layer made of an insulating member is formed between the production substrate and the film formation layer. For example, as the intermediate layer, a heat-resistant nonionic conductive material such as silicon dioxide, zirconium oxide, or titanium oxide is used.

DESCRIPTION OF SYMBOLS 1 Container 2 Electrode substrate 3 Carbon nanotube 4 Electrode member 5 Separator 11 Manufacturing substrate 12 Film-forming layer 13 Catalyst layer 14 Carbon nanotube

Claims (6)

An electrode member in which a plurality of at least double wall carbon nanotubes and multiwall carbon nanotubes are arranged vertically on the surface of the electrode substrate,
An electrode member using carbon nanotubes, wherein the ratio of the double wall carbon nanotubes to the total carbon nanotubes is in the range of 1/3 to 2/3. An electrode member in which a plurality of at least double wall carbon nanotubes and multiwall carbon nanotubes are arranged vertically on the surface of the electrode substrate,
At least an aluminum oxide layer and a catalyst layer are sequentially disposed on the surface of the electrode substrate,
Further, a large number of the double-walled carbon nanotubes and multi-walled carbon nanotubes are arranged vertically on the surface of the catalyst layer so that the ratio of the double-walled carbon nanotubes to the total carbon nanotubes is in the range of 1/3 to 2/3. The electrode member using the carbon nanotube characterized by having performed. The electrode member using carbon nanotubes according to claim 1 or 2, wherein the formation density of multi-wall carbon nanotubes is 10 ¹⁰ to 10 ¹³ pieces / cm ² .   An electrode member using the carbon nanotube according to any one of claims 1 to 3 is disposed in a container so that the carbon nanotubes face each other, and a separator is disposed between the two electrode members. An electric double layer capacitor filled with an electrolyte. A method for producing an electrode member in which a plurality of at least double-wall carbon nanotubes and multi-wall carbon nanotubes are arranged,
After at least an aluminum oxide layer and a catalyst layer are sequentially formed on the surface of the production substrate, a large number of the double wall carbon nanotubes and multi-wall carbon nanotubes are vertically formed on the surface of the catalyst layer, and the double wall for the carbon nanotubes. Formed so that the proportion of carbon nanotubes is in the range of 1/3 to 2/3,
Next, a carbon nanotube formed on the surface of the production substrate is transferred to an electrode substrate to obtain an electrode member. The method for producing an electrode member using carbon nanotubes according to claim 5, wherein the formation density of the multi-wall carbon nanotubes is 10 ¹⁰ to 10 ¹³ pieces / cm ² .

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