JP5303235B2 - Electrode for electric double layer capacitor and method for manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrode for electric double layer capacitor excellent in capacitance characteristics, and to provide a method for manufacturing the same. <P>SOLUTION: The electrode for electric double layer capacitor is prepared by integrating a sheet 2, in which carbon nano tube (SGCNT) whose specific surface area is 600 to 2,600 m<SP>2</SP>/g is paper-formed, with an etching foil 1 through an irregular section 1a formed on a surface of the foil 1 composing a collector; or the electrode for electric double layer capacitor is prepared by integrating SGCNT 4, grown with a catalyst particle as a nucleus on a substrate 3, with the foil 1 through the section 1a formed on the surface of the foil 1. In order to manufacture these electrodes, the sheet 2 of the SGCNT or the substrate 3 on which the sheet 2 of the SGCNT is grown is superposed on the section 1a on the surface of the foil 1 and these are pressurized at a pressure of 0.01 to 100 t/cm<SP>2</SP>, thereby integrating the SGCNT with the etching foil. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to an electrode for an electric double layer capacitor that has been improved so as to obtain excellent capacitance characteristics, and a method for manufacturing the same.

  The electric double layer capacitor uses a polarizable electrode such as activated carbon as positive and negative electrodes, and an electrolytic solution obtained by dissolving quaternary onium salt of boron tetrafluoride or phosphorus hexafluoride in an organic solvent such as propylene carbonate. In such an electric double layer capacitor, the electric double layer generated at the interface between the electrode surface and the electrolyte has an electrostatic capacity, and there is no reaction involving ions like a battery. There is an advantage that the capacity deterioration due to the discharge cycle is small.

  For this reason, the electric double layer capacitor is indispensable for, for example, a power storage system of a fuel cell vehicle or a hybrid vehicle, particularly a regenerative energy storage system that recovers energy dissipated during deceleration. However, since the energy density due to the double layer capacity is lower than that of the battery and it is significantly insufficient as a power source for electric vehicles, it is essential to further improve the storage capacity density.

  This electric double layer capacitor includes an electrode on which an electric double layer is formed, that is, a polarizable electrode, an electrolytic solution, a separator that allows only ions of the electrolytic solution to pass through, and a collector electrode that collects and extracts charges from the polarizable electrode. And a pair of polarizable electrodes having a collector electrode on the back surface, and a structure in which an electrolytic solution is sealed in a structure opposed to each other with a separator interposed therebetween.

  For such an electric double layer capacitor, various proposals have been made for the purpose of providing an electric double layer capacitor having a large storage capacity. For example, there is an attempt to use a carbon nanotube as a polarizable material for an electric double layer capacitor (see Patent Document 1).

  However, in the invention described in Patent Document 1 as described above, there is a problem that an electrode having good capacity characteristics cannot be obtained because a binder which is a resin component is used.

In order to improve this, as shown in Patent Document 2, a conductive fiber or a conductive tube is bonded and joined to the electrode substrate in a substantially parallel manner without using a material such as a binder or a conductive auxiliary material. Proposals have also been made. However, the invention of Patent Document 2 is such that a conductive fiber or a conductive tube is adhered and bonded to an electrode substrate using an electrodeposition method such as electrophoresis, and the conductive fiber is bonded to the electrode substrate. Or it was complicated and time-consuming, for example, a solution obtained by dispersing a conductive tube in an organic solvent while stirring with ultrasonic waves.
JP 2005-136020 A JP 2006-222175 A Science Vol.306, p.1362-1364 (2004) Chemical Physics Letters 403, p.320-323 (2005) Journal of Physical Chemistry B2004,108, p.18395-18397

  The present invention has been proposed to solve the conventional problems as described above, and the object thereof can be manufactured by a simple process compared to the invention of Patent Document 2, An object of the present invention is to provide an electrode for an electric double layer capacitor having excellent capacity characteristics and a method for producing the same.

In order to solve the above-mentioned problems, the present inventors have repeatedly investigated an electrode for an electric double layer capacitor capable of obtaining excellent capacity characteristics when carbon nanotubes are used as a polarizable material for an electric double layer capacitor. As a result, the present invention has been completed. In particular, conventional carbon nanotubes having a specific surface area of 500 m ² / g or less form bundles (bundles) due to strong van der Waals forces and are micro-aggregated, so that it is difficult to achieve high dispersion. Carbon nanotubes having a large surface area of 600 to 2600 m ² / g are focused on the point that high dispersion can be expected because they have almost no bundle formation or micro-aggregation due to van der Waals force. In the present specification, a carbon nanotube having a specific surface area of 600 to 2600 m ² / g is referred to as SGCNT.

That is, in the electrode for an electric double layer capacitor of the present invention, a sheet obtained by paper- making carbon nanotubes having a specific surface area of 600 to 2600 m ² / g without using a binder constitutes a current collector and pressure is applied to the surface. A base material having a convex portion that is bent and bites into the sheet is integrated with the convex portion without using an adhesive . Further, an electrode for an electric double layer capacitor using a porous metal body as the substrate, and an electrode for an electric double layer capacitor using foamed nickel or aluminum as the substrate are also one embodiment of the present invention.

The electrode for an electric double layer capacitor according to the present invention is a sheet in which SGCNT is paper-molded without using a binder, is formed on the surface of an etching foil constituting a current collector and is bent under pressure. It is characterized in that it is integrated with the etching foil and the adhesive without using an adhesive by the convex portion that bites into the surface. In addition, an electrode for an electric double layer capacitor in which SGCNT grown using catalyst particles on a substrate as a nucleus is integrated with the etching foil without using an adhesive by a convex portion formed on the surface of the etching foil is also provided. It is one embodiment of the invention.

Furthermore, in order to form these electrodes, a sheet obtained by papermaking without using a binder or a substrate on which SGCNT has been grown is superposed on the concave and convex portions on the surface of the etching foil, and these are pressed to apply SGCNT and the etching foil. Is also an embodiment of the present invention, in which an electrode for an electric double layer capacitor is manufactured without using an adhesive .

  Note that when SGCNT is formed by paper making, it is also an aspect of the present invention to use a small amount of a resin or other material such as a binder or a conductive auxiliary material in order to prevent the SGCNTs from being dissipated. Even in this case, the amount of the binder used can be greatly reduced compared to the case where the SGCNT and the current collector are integrated using the binder, and the capacity characteristics can be improved accordingly.

  Further, an electrode for an electric double layer capacitor in which aluminum is sputtered on at least a current collector side surface of the sheet prior to the integration is also an aspect of the present invention.

Further, a sheet formed by papermaking SGCNT is a carbon nanotube aggregate (SGCNT) having a specific surface area of 600 to 2600 m ² / g and a density of 0.5 to 1.5 g / cm ³ , in which the SGCNT is highly dispersed and deposited. An electrode for an electric double layer capacitor which is an aggregate) is also one embodiment of the present invention.

Such a high-density carbon nanotube aggregate (high-density SGCNT aggregate) can be obtained as follows. That is, a predetermined amount of CNT (single layer SGCNT) having a specific surface area of 600 to 2600 m ² / g is mixed in a predetermined amount of isopropyl alcohol and stirred with a homogenizer to obtain a dispersion solution. This dispersion solution is introduced into a predetermined metal chamber, and an ultrahigh pressure of 100 to 280 MPa is applied. The highly dispersed solution obtained by this ultra-high pressure treatment is filtered under reduced pressure using PTFE filter paper (diameter: 35 mm, average pore 0.2 μm) to obtain a paper-molded sheet. This sheet is further rolled at a press pressure of 0.01 to 100 t / cm ² to obtain a densified sheet (high density SGCNT sheet).

Then, the high density SGCNT sheet obtained as described above is superposed on the protrusions on the surface of the etching foil, and these are pressed to integrate the SGCNT and the etching foil, thereby forming the electrode for the electric double layer capacitor. Can be obtained. In addition, the paper-molded sheet as described above is superimposed on the protrusions on the surface of the etching foil without being rolled, and these are pressed to integrate the CNT and the etching foil, thereby increasing the density and integration. Can be performed simultaneously.

In the present specification, the “high density SGCNT aggregate” means that SGCNT is highly dispersed and deposited, the specific surface area is 600 to 2600 m ² / g, and the density is 0.5 to 1.5 g / cm ³ . The SGCNT aggregate is referred to, and the “high density SGCNT sheet” refers to a sheet formed from the high density SGCNT aggregate. The “high density SGCNT sheet” is also referred to as “high density SGCNT paper”.

According to the present invention having the above-described configuration, since the SGCNT and the etching foil are integrated in a state where the convex portion of the etching foil constituting the current collector bites into the SGCNT, a resin-based binder or other binder There is no need to use a material such as a conductive auxiliary material, and the conductive material is in direct contact with the current collector, so that the electrical resistance can be reduced and an electrode for an electric double layer capacitor having excellent capacitance characteristics can be obtained. Can do.

The same applies not only to the etching foil, but also to the case where a base material having a convex portion on the surface constituting the current collector, particularly a porous metal body typified by foamed nickel, is used. If it is used, the apparent density is lowered due to the presence of vacancies inside the metal body, so that it becomes a lighter current collector and an electrode for an electric double layer capacitor having excellent capacity characteristics can be obtained. In particular, when nickel foam is used, the electric double layer has an apparent density of 0.2 g / cc (porosity 98%) and is lighter than an etching foil (at least about 1.0 g / cc with an Al etching foil) and has excellent capacity characteristics. A capacitor electrode can be obtained.

In addition, SGCNT bundles and macro-aggregation are loosened by performing ultra-high pressure treatment as a sheet obtained by paper-molding SGCNT, SGCNT is highly dispersed and deposited, and the specific surface area is 600-2600 m ² / g and the density By using an SGCNT aggregate (high density SGCNT aggregate) of 0.5 to 1.5 g / cm ³ , an electrode for an electric double layer capacitor having better electrical characteristics can be obtained.

(1) Electrode double layer capacitor electrode manufacturing method (1-1) First method FIG.
The outline of this method is that a carbon nanotube (SGCNT) having a specific surface area of 600-2600 m ² / g is formed by paper making (paper making) without using a binder to form an SGCNT sheet (also called paper). The SGCNT sheet 2 is pressed against a foil of a current collector such as an aluminum foil 1 (hereinafter also referred to as an etching foil 1) that has been subjected to an etching process, and the SGCNT sheet 2 and the etching foil 1 are integrated to produce an electrode. Is. The SGCNT used in the present invention will be described later.

  More specifically, a predetermined amount of SGCNT is measured, mixed with a predetermined amount of methanol, and stirred for about 30 seconds with a general-purpose mixer to prepare an SGCNT / methanol dispersion. The dispersion is filtered under reduced pressure using PTFE filter paper (diameter: 35 mm, average pore size 0.2 μm) to obtain a paper-molded SGCNT sheet. The thickness of the SGCNT sheet 2 is such that the thickness of the SGCNT layer formed after pressing is about 1 to 60 μm (more specifically, the thickness of the carbon nanotube layer required for the electrode of the electric double layer capacitor). As such, the deformation due to the press is taken into consideration beforehand.

The SGCNT sheet 2 is cut to the same size as the current collector and placed on the etched aluminum foil 1 which is the current collector, and an aluminum foil having a flat surface that is not subjected to the etching treatment separately prepared from the top (see FIG. (Not shown) and pressed from the top and bottom of the foil at a pressure of 10 t / cm ² for 1 minute.

The pressure to be pressed is preferably 0.01 to 100 t / cm ² , and the pressure is applied to the enlarged uneven portion 1a of the etched aluminum foil 1 by this pressing. As a result, as shown in FIG. As a result of the pressure being applied to the bent sheet and the convex portion biting into the paper-molded SGCNT sheet 2, excellent bondability can be imparted.

(1-2) Second Method ... FIG.
The outline of this method is that the metal fine particles such as iron fine particles and cobalt fine particles are placed on the surface of the base material 3 such as a silicon base material as a catalyst, SGCNT is generated from the catalyst, and the SGCNT structure 4 is formed. The SGCNT structure 4 is pressed against a predetermined etching foil 1 to produce an electrode.

More specifically, on the SGCNT structure 4 grown on the substrate 3 by a known CVD method (chemical vapor deposition method), an etched aluminum foil 1 that is a current collector of the same size as the substrate 3 is used. Are sandwiched between separately prepared aluminum foils (not shown) having a smooth surface, and pressed for 1 minute at a pressure of 10 t / cm ² from the vertical direction of the foils. After pressing, the smooth aluminum foil that has been sandwiched is removed, and the current collector (etching foil 1) attached to the substrate 3 is peeled off by the pressing process, whereby the SGCNT structure 4 is transferred to the surface of the current collector.

In the second method as well, the pressing pressure is preferably 0.01 to 100 t / cm ² , and this pressing applies pressure to the enlarged uneven portion 1a of the etched aluminum foil. It is considered that excellent bonding properties can be imparted by applying a pressure to the part and bending the convex part into the SGCNT structure 4.

(1-3) Pressing method As a pressing method, as long as a pressure of 0.01 to 100 t / cm ² can be applied, in addition to a flat press, other methods such as a roll press can be used. it can.

(1-4) Carbon nanotube The carbon nanotube used for the electrode material of the present invention preferably has a specific surface area of 600 to 2600 m ² / g. Such a large specific surface area is desirable in order to make the capacitance of the electrochemical capacitor higher and to increase the energy density. The carbon nanotubes may be single-walled, double-walled, multi-walled with three or more layers, and may be mixed.

Conventionally, the specific surface area of the carbon nanotube used for the electrode of the electrochemical capacitor has been about 500 m ² / g at most, but the electrochemical capacitor of the present invention has a specific surface area of 600 m in order to achieve the intended purpose. ^Use very large carbon nanotubes of ² / g or more. Such a large specific surface area of the carbon nanotubes can be achieved by using those in which bundles are not formed between the carbon nanotubes, or by selectively using very few carbon nanotubes even if they are formed.

In this case, carbon nanotubes with no bundle or very few bundles can be obtained by using, for example, the methods described in Non-Patent Document 1, Non-Patent Document 2, and the like. Further, for a commercially available HiPco (registered trademark, manufactured by Carbon Nanotechnologies) having a specific surface area of several hundred m ² / g, for example, a bundle structure as described in Non-Patent Document 3 is released. It can also be obtained by using a method of applying various means. In the case of a single layer, the SGCNT used in the present invention preferably has a diameter of 2 to 4 nm, a length of 0.1 to 10 mm, and a purity of 80 to 99.98%. In the case of two or more layers, those having a diameter of 4 to 10 nm, a length of 0.1 to 10 mm, and a purity of 80 to 99.98% are preferable.

  Moreover, as SGCNT used for the electrochemical capacitor of this invention, it is preferable to use what has semiconducting property in addition to providing the above large specific surface areas. The reason is that, when a capacitor using SGCNT for both electrodes is manufactured, a high capacitance can be obtained when a high voltage is applied to the capacitor.

Moreover, as SGCNT used for the electrochemical capacitor of this invention, a density of 0.2-1.5 g / cm < ³ > is preferable. This is because if the density is too lower than this range, the material becomes mechanically brittle and sufficient mechanical strength cannot be obtained, and the capacity density per volume becomes low. On the other hand, if it is higher than this range, there is no space for the electrolytic solution to enter, resulting in a decrease in capacity density.

(2) Etching foil As the etching foil 1, a current collector of a metal foil such as an aluminum foil whose surface is enlarged by a chemical etching or an electrochemical etching method is used. In this case, the thickness of the etching foil as the current collector is desirably 10 μm to 100 μm. If the thickness is 10 μm or less, it is difficult to construct a capacitor cell due to insufficient strength of the current collector, and if it is too thick, the capacity density (or energy density) per cell decreases.

  Further, the shape of the uneven portion 1a formed on the etching foil 1 is preferably such that the tip of the convex portion bites into the sheet at the time of pressing, or the convex portion tip is deformed and entangled with the fibers constituting the sheet. A pointed rod-like (needle-like) shape is preferable to the portion 1a having a gentle hill-like shape.

  Further, the height of the concavo-convex portion 1a (the distance from the tip of the convex portion to the bottom portion of the concave portion) is lower than the thickness of the SGCNT layer (for example, about 1 to 60 μm), and the current collecting layer is pressed It sets so that it may coat | cover reliably with the SGCNT layer formed later. In addition, it is necessary to consider the thickness (about 10 μm to 100 μm) of the etching foil that is a current collector. In the case of a thin etching foil, the thickness of the etching foil is maintained within 2/3 of the thickness. Preferred above.

(3) Ultra-high pressure treatment A predetermined amount of CNT (single layer SGCNT) having a specific surface area of 600 to 2600 m ² / g is mixed in a predetermined amount of isopropyl alcohol, and stirred with a homogenizer to obtain a dispersion solution. This dispersion solution is introduced into a predetermined metal chamber, and an ultrahigh pressure of 100 to 280 MPa is applied. The highly dispersed solution obtained by this ultra-high pressure treatment is filtered under reduced pressure using PTFE filter paper (diameter: 35 mm, average pore 0.2 μm) to obtain a paper-molded sheet. This sheet is further rolled at a press pressure of 0.01 to 100 t / cm ² to obtain a densified sheet (high density SGCNT sheet).

  Then, the high density SGCNT sheet obtained as described above is overlaid on the concavo-convex portions on the surface of the etching foil, and these are pressed to integrate the SGCNT and the etching foil, thereby forming the electrode for the electric double layer capacitor. Can be obtained. In addition, the paper-molded sheet as described above is overlaid on the concavo-convex portions on the surface of the etching foil without rolling, and these are pressed to integrate the CNT and the etching foil, thereby increasing the density and integration. Can be performed simultaneously.

(3-1) Ultra High Pressure Treatment In the ultra high pressure treatment, the dispersion solution obtained as described above is introduced into a predetermined metal chamber, and an ultra high pressure of 100 to 280 MPa is applied. As the metal chamber, a slit chamber, a ball collision chamber, or the like can be used.

  By applying an ultra-high pressure as described above, the dispersion solution and the walls of the metal chamber, the slits installed in the dispersion solution and the metal chamber, or the balls introduced into the dispersion solution and the metal chamber, etc. have high energy. This causes the carbon nanotube bundles and macroaggregation to be loosened and more highly dispersed. Further, by applying an ultra-high pressure, the solutions are also mixed with high energy, so that the bundles and macro-aggregation of the carbon nanotubes are also loosened and more highly dispersed.

(3-2) Sheeting treatment In the sheeting treatment, the high-dispersion solution obtained by the above ultra-high pressure treatment is filtered under reduced pressure using PTFE filter paper (diameter: 35 mm, average pore size 0.2 μm), and papermaking molding Then, after obtaining a sheet, this sheet is dried under reduced pressure at 60 ° C. for 3 hours.

(3-3) Rolling process The rolling process is performed using a roll press that rolls between two rolls, a vertical press that applies pressure from above and below in parallel, and the pressing pressure is 0.01 to 100 t / cm. ² is preferred. The reason is that if the pressure is too weak, densification is not sufficient, and if it is too high, the CNT sheet is defective.

[1. Example using etching foil)
Example 1
About 50 mg of SGCNT was weighed, mixed with 50 ml of methanol, and stirred with a general-purpose mixer for about 30 seconds to prepare an SGCNT / methanol dispersion. This dispersion was filtered under reduced pressure using PTFE filter paper (diameter: 35 mm, average pore size 0.2 μm) to obtain a paper-molded SGCNT sheet. Cut this to the same size as the current collector and place it on the etched aluminum foil, unetched aluminum foil, copper foil, and platinum foil as the current collector. It pressed from the direction at a pressure of 10 t / cm ² for 1 minute.

(Example 2)
Each of the etched aluminum foil, unetched aluminum foil, copper foil, and platinum foil was placed on the SGCNT structure grown on the substrate by CVD as a current collector of the same size as the substrate. A high pressure press was performed under the same conditions as in Example 1. After pressing, the sandwiched aluminum foil was removed, the current collector attached to the substrate was removed by pressing, and the SGCNT structure was transferred to the surface of the current collector.

(Comparative Example 1)
About 50 mg of SGCNT was weighed, mixed with about 10 mg of binder (PTFE) dispersion and about 10 mg of ketjen black as a conductive auxiliary material, and kneaded in a mortar. Then, the SGCNT sheet was obtained by stretching with a biaxial roller.

(Test results)
About said Example 1-2, when the adhesion state immediately after a high pressure press process and the adhesion state after being immersed in methanol after a high pressure press process were observed, the result as shown in Table 1 was obtained. As is apparent from Table 1, it was found that when the etching foil according to the present invention was used, the adhesion state was better than when other current collectors were used.

  Moreover, about the said Examples 1-2 and the comparative example 1, when the capacity density of the electrode which adhere | attached the etching foil which concerns on this invention as a collector by the high voltage | pressure press process was measured, the electrodes of Examples 1-2 were compared. Compared to Example 1, a capacity density about 20-30% higher was obtained. This is presumed that the binder material in Comparative Example 1 hinders improvement in capacity density.

[2. Example using nickel foam)
Up to this point, an example in which an etching foil is used as a base material that constitutes a current collector and has an uneven portion on the surface has been shown. Well, the knowledge about the example and some other ideas and effects will be described below.

(Example 3)
SGCNT sheet formed by papermaking in the same manner as in Example 1, and nickel foam as a current collector with a porosity of 98% and a density of 0.18 g / cm ³ (here, manufactured by Sumitomo Electric Industries, Ltd.) Pressing was performed in the same manner as in Example 1 using Celmet (trademark).

Example 4
Further, the same SGCNT structure as in Example 2 and the above-mentioned Celmet having a porosity of 98% and a density of 0.18 g / cm ³ were used as the current collector and transferred in the same manner as in Example 2.

(Test results)
About Examples 3-4, when the adhesion state immediately after high-pressure press processing and the adhesion state after being immersed in methanol after high-pressure press processing were observed, the result as shown in Table 2 was obtained.

  As is clear from Table 2, it was found that even when the metal foam was used in the present invention, the adhesion state was good as in the case of using the etching foil shown in Table 1.

[3. (Reducing resistance)
Moreover, about the contact resistance value after joining, both the SGCNT paper electrode (Example 1) obtained by press joining to the etching aluminum foil and the SGCNT structure electrode (Example 2) are used for the same kind of etching aluminum foil and carbon paste. It was found that a lower contact resistance can be obtained than the activated carbon electrode adhered. In addition, in the state which has not applied the voltage, the activated carbon electrode and resistance were comparable. Details will be described below.

(Comparative Example 2)
The SGCNT sheet formed by the same method as in Example 1 was sandwiched between aluminum foils without placing a current collector and pressed at a pressure of 10 t / cm ² from the top and bottom of the foil for 1 minute, and the same size as the current collector Cut out. Then, using the etched aluminum foil similar to that of Example 1 as a current collector, a carbon paste was applied to the adhesion surface of the cut SGCNT sheet, and a high-pressure pressed SGCNT sheet was adhered thereon, The electrode was dried at 120 ° C. for 1 hour under pressure to obtain an electrode (SGCNT paper paste adhesive electrode).

(Test results)
When the electrical resistance of the electrodes of Example 1 and Comparative Example 2 was measured by the AC impedance method, the results shown in Table 3 were obtained. Moreover, about the comparison of Example 2 and Comparative Example 2, the same numerical value as the comparison result with Example 1 was obtained.

  As can be seen from Table 3, the electrode of Example 1 manufactured by the high-pressure press method according to the present invention exhibits a resistance that is 1/10 lower than the electrode bonded with the carbon paste of Comparative Example 2. It became clear. This is presumably because, unlike the electrode of Comparative Example 2, the electrode of Example 1 does not have the resistance component of the carbon paste layer and the interface contact resistance component of the carbon paste and SGCNT.

[4. (Improvement of power density)
Moreover, when the energy density and power density of the laminated cell using the electrode of Example 1 were evaluated, it was found that the contact resistance was low and a high power density was obtained. In the state where voltage was applied, the resistance was lower than that of the activated carbon electrode. Details will be described below.

(Example 5)
The electrode (SGCNT paper electrode) produced in Example 1 was used for both electrodes, and an electric double layer capacitor element was produced via a cellulose separator (electrode area: 2.1 cm ² ). Then, after impregnating the element as an electrolyte with a propylene carbonate solution containing 1M (= 1 mol / dm ³ ) tetraethylammonium tetrafluoroborate as an electrolytic solution, the element was heat sealed using a laminate film, and an evaluation cell (SGCNT paper). Cell).

(Comparative Example 3)
About 50 mg of activated carbon for electric double layer capacitor activated with water vapor was weighed, mixed with about 10 mg of binder (PTFE) dispersion and about 10 mg of ketjen black as a conductive auxiliary material, and kneaded in a mortar. Then, it extended with the biaxial roller and obtained the activated carbon sheet. The sheet thus obtained was bonded to the etched aluminum foil used in Example 1 with a general-purpose carbon paste to produce an activated carbon electrode. This activated carbon electrode was cut into the same area as the SGCNT paper electrode of Example 5, and an evaluation cell (activated carbon cell) was produced in the same manner as in Example 5.

(Test results)
When the contact resistance, the electron transfer resistance, and the ion diffusion resistance were measured for the cells of Example 5 and Comparative Example 3 by the electrochemical alternating current impedance method, the results shown in Table 4 were obtained.

  As is apparent from Table 4, the SGCNT paper cell using the etching foil according to the present invention has smaller resistance components than the activated carbon cell, namely, contact resistance, electron transfer resistance, and ion diffusion resistance. The resistance was reduced by about 60% compared to the activated carbon cell.

  Moreover, when the energy density and power density were measured about the cell of said Example 5 and the comparative example 3, the result as shown in FIG. 3 was obtained. As is clear from FIG. 3, the cell of Example 5 has a smaller slope of the plot than that of the cell of Comparative Example 3, and thus it became clear that a high energy density can be maintained even in a high power density region. This is presumed to be due to the fact that the capacity retention of the cell was increased because the three resistance components of the cell of Example 5 were smaller than the resistance component of Comparative Example 3 as shown in Table 4.

[5. (Improvement of energy density)
Moreover, when the energy density and power density of the cell of Example 5 were evaluated, it was found that the capacity density was high and a high energy density was obtained.

(Comparative Example 4)
Single-walled carbon nanotubes (SWCNT) grown by the HiPco method were pressed in the same manner as in Example 1 to obtain an electrode (SWCNT paper electrode). Using this electrode for both electrodes, an evaluation cell (SWCNT paper cell) was produced in the same manner as in Example 5.

(Test results)
When the energy density and power density of the cells of Example 5 and Comparative Example 4 were measured, the results shown in FIG. 3 were obtained. As can be seen from FIG. 3, the cell of Example 5 was found to have a higher energy density in a wider power density region than the cell of Comparative Example 4. This is presumably because SGCNT used in Example 5 has a higher capacity density than SWCNT used in Comparative Example 4.

[6. Resistance reduction by sputtering)
Further, it was found that the resistance value of the obtained electrode is reduced by sputtering a metal such as Al, Au, Pt on the SGCNT paper or structure before performing the press bonding of the present invention. Details will be described below.

(Example 6)
Aluminum was sputtered on one side of the SGCNT sheet formed by papermaking in the same manner as in Example 1 by magnetron sputtering. Using the sputtered surface as the contact surface with the current collector and using the aluminum foil etched in the same manner as in Example 1 as the current collector, pressing was performed in the same manner as in Example 1, and the electrode (SGCNT paper Al sputter electrode) ) Using this electrode for both electrodes, an evaluation cell (SGCNT paper Al sputter cell) was produced in the same manner as in Example 5.

(Test results)
When the contact resistance, the electron transfer resistance, and the ion diffusion resistance were measured for the cells of Example 5 and Example 6 by the electrochemical alternating current impedance method, the results shown in Table 5 were obtained.
As is clear from Table 5, the contact resistance of the cell of Example 6 was greatly reduced.

  Moreover, when the energy density and power density were measured about the cell of Example 5 and Example 6, the result as shown in FIG. 4 was obtained. As can be seen from FIG. 4, the cell of Example 6 was able to maintain a higher energy density even in the high power density region than the cell of Example 5. This is presumed to be due to the fact that the cell's capacity retention was increased because the contact resistance of the cell of Example 6 shown in Table 5 was smaller than that of the cell of Example 5.

[7. (Improvement of power density)
Subsequently, when the energy density and power density of the laminate-type cell using the electrode of Example 2 were evaluated, all of contact resistance, electron transfer resistance and ion diffusion resistance were lower than in Example 5 and high power. It was found that density was obtained. Details will be described below.

(Example 7)
Using the same SGCNT structure as in Example 2 and the aluminum foil etched in the same manner as in Example 2 as a current collector, transfer was performed in the same manner as in Example 2 to obtain an electrode (SGCNT structure electrode). It was. Using this electrode for both electrodes, an evaluation cell (SGCNT structure cell) was produced in the same manner as in Example 5.

(Test results)
When the contact resistance, the electron transfer resistance, and the ion diffusion resistance were measured by the electrochemical alternating current impedance method for the cells of Example 5 and Example 7, the results shown in Table 6 were obtained.

  As is apparent from Table 6, in the cell of Example 7, all three resistance values of contact resistance, electron transfer resistance, and ion diffusion resistance are further reduced as compared with Example 5, and particularly about contact resistance, about 50 % Reduction.

  The SGCNT structure used in the cell of Example 7 has a structure in which the surface in contact with the current collector is smoother than the SGCNT paper used in the cell of Example 5, and the SGCNTs are regularly arranged in the same direction ( High orientation). It is presumed that the contact resistance is reduced due to the good smoothness of the SGCNT structure, and the electron transfer resistance is reduced due to the large number of contact points between SGCNTs due to the high orientation of the SGCNT structure. Furthermore, since this high orientation improves the ion diffusivity, it is presumed that the ion diffusion resistance is also reduced.

  Moreover, when the energy density and power density were measured about the cell of Example 5 and Example 7, the result as shown in FIG. 5 was obtained. As can be seen from FIG. 5, the cell of Example 7 was able to maintain a higher energy density even in the high power density region than the cell of Example 5. This is presumed to be because the capacity retention of the cell was increased because the three types of resistance of the cell of Example 7 shown in Table 6 were smaller than those of the cell of Example 5.

[8. Example using high-density SGCNT sheet]
A carbon nanotube electrode obtained by press-bonding a high-density carbon nanotube sheet (high-density SGCNT sheet) obtained by ultra-high pressure treatment of carbon nanotubes (SGCNT) and then paper-molding to an etched aluminum foil has a high energy density. And have a power density. Details will be described below.

(Example 8)
100 mg of the same SGCNT as in Example 1 was taken and mixed in 1 L of isopropyl alcohol, and stirred for about 2 minutes with a general-purpose mixer to obtain a dispersion solution. This dispersion solution was introduced into a predetermined metal chamber, an ultrahigh pressure of 200 MPa was applied, and the resulting high dispersion solution was filtered under reduced pressure using PTFE filter paper (diameter: 35 mm, average pore size: 0.2 μm). A molded sheet was obtained. This sheet was dried under reduced pressure at 60 ° C. for 3 hours. The obtained sheet was press-bonded to the same aluminum foil (high density SGCNT paper electrode) in the same manner as in Example 1.

(Test results)
When the sheet density, the sheet density after press bonding and the electrolyte solution impregnation were examined for the high density SGCNT sheet produced in Example 8 and the SGCNT sheet produced in Example 1, the results shown in Table 7 were obtained. Obtained. As is clear from Table 7, the high-density SGCNT sheet obtained in Example 8 shows a higher sheet density than the SGCNT sheet obtained in Example 1. In addition, the sheet density after press bonding and electrolytic solution impregnation was extremely high as compared with Example 1, indicating that a high-density SGCNT sheet was obtained.

Example 9
Using the high-density SGCNT paper electrode produced in Example 8, a laminate-type cell for evaluation (high-density SGCNT paper cell) was produced in the same manner as in Example 5.

(Test results)
When the energy density and the power density were measured for each of the cells of Example 8, Example 5, Comparative Example 3, and Comparative Example 4, results as shown in FIG. 6 were obtained. As is clear from FIG. 6, the cell of Example 8 was found to have greatly improved energy density and power density per unit volume as compared with the cell of Example 5. This is presumably because SGCNT is densified.

(Example 10)
Using the high-density SGCNT sheet produced by the method of Example 8, aluminum was sputtered after aluminum sputtering by the same method as in Example 6 to obtain an electrode (high-density SGCNT paper Al sputter electrode). Using this electrode for both electrodes, an evaluation cell (high density SGCNT paper Al sputter cell) was produced in the same manner as in Example 5.

(Test results)
When the energy density and the power density were measured for each of the cells of Example 10, Example 9, Example 5, and Example 6, results as shown in FIG. 7 were obtained. As is clear from FIG. 7, the cell of Example 10 was found to have greatly improved energy density and power density per unit volume compared to the cell of Example 6. Thus, it was found that a larger power density can be obtained by press bonding the densified SGCNT after aluminum sputtering.

[9. Others]
In the case of an SGCNT structure, it can be controlled to have an arbitrary length and thickness by patterning the catalyst at the time of production, and by using an SGCNT structure produced by patterning the catalyst in a predetermined shape, a predetermined shrinkage can be achieved. It is possible to obtain an SGCNT electrode patterned in a predetermined shape by contracting at a rate.

  Moreover, about SGCNT on the SGCNT electrode produced by the press bonding method of the present invention, it was confirmed by Raman spectroscopy that the SGCNT was not damaged before and after bonding. That is, it was confirmed that there was no change in the G / D ratio calculated from the Raman spectrum before and after bonding.

Sectional drawing which shows typically an example of the manufacturing method of the electrode for electric double layer capacitors of this invention. Sectional drawing which shows typically the other example of the manufacturing method of the electrode for electric double layer capacitors of this invention. In the Example of this invention, the figure which shows the relationship between the energy density of Example 5, Comparative Example 3, and Comparative Example 4 and power density. In the Example of this invention, the figure which shows the relationship between the energy density of Example 5 and Example 6, and a power density. In the Example of this invention, the figure which shows the relationship between the energy density of Example 5 and Example 7, and a power density. In the Example of this invention, the figure which shows the relationship between the energy density of Example 9 and Example 5, Comparative Example 3, and Comparative Example 4 and power density. In the Example of this invention, the figure which shows the relationship between the energy density of Example 9, Example 10, Example 5, and Example 6 and power density.

Claims (15)

A sheet formed by papermaking carbon nanotubes having a specific surface area of 600-2600 m ² / g without using a binder has a convex portion that forms a current collector and is bent due to pressure applied to the surface. An electrode for an electric double layer capacitor, which is integrated without using an adhesive by a base material and a convex portion thereof.   The electrode for an electric double layer capacitor according to claim 1, wherein a porous metal body is used as the substrate.   The electric double layer capacitor electrode according to claim 1, wherein foamed nickel is used as the substrate.   The electrode for an electric double layer capacitor according to claim 1, wherein the substrate is made of aluminum. A sheet obtained by paper- making carbon nanotubes having a specific surface area of 600-2600 m ² / g without using a binder is formed on the surface of the etching foil constituting the current collector and is bent under pressure. An electrode for an electric double layer capacitor, characterized in that the electrode is integrated with the etching foil without using an adhesive via a protruding protrusion. A sheet obtained by papermaking the carbon nanotubes having a specific surface area of 600-2600 m ² / g without using a binder is deposited with the carbon nanotubes being highly dispersed and having a density of 0.5-1.5 g / cm ³ . The electrode for an electric double layer capacitor according to any one of claims 1 to 5 , wherein the electrode is an aggregate of carbon nanotubes. Carbon nanotubes having a specific surface area of 600 to 2600 m ² / g grown using catalyst particles on the substrate as a nucleus are formed on the surface of the etching foil constituting the current collector and are bent under pressure. An electrode for an electric double layer capacitor, characterized in that the electrode is integrated with the etching foil without using an adhesive by a convex portion that bites into the nanotube. The electrode for an electric double layer capacitor according to any one of claims 1 to 7 , wherein aluminum is sputtered on at least a current collector-side surface of the sheet or substrate. The electrode for an electric double layer capacitor according to any one of claims 1 to 8 , wherein the carbon nanotube contains a semiconducting carbon nanotube. The density of the carbon nanotubes, 0.2 to 1.5 g / cm ³ according to claim 1 to an electric double layer capacitor electrode according to any one of claims 9, characterized in that. A sheet formed by papermaking carbon nanotubes having a specific surface area of 600 to 2600 m ² / g without using a binder is formed on the surface of the etching foil constituting the current collector and is bent under pressure to form the sheet. A method for producing an electrode for an electric double layer capacitor, wherein the carbon nanotube and the etching foil are integrated without using an adhesive by pressing against a projecting portion. A sheet obtained by papermaking the carbon nanotubes having a specific surface area of 600-2600 m ² / g without using a binder is deposited with the carbon nanotubes being highly dispersed and having a density of 0.5-1.5 g / cm ³ . method for producing an electric double layer capacitor electrode according to claim 1 1, characterized in that a certain aggregate of carbon nanotubes. A substrate on which carbon nanotubes having a specific surface area of 600 to 2600 m ² / g with catalyst particles as nuclei is grown on the surface is formed on the convex portion of the etching foil surface constituting the current collector so that the carbon nanotubes face each other. overlay, integrated without using an adhesive and the carbon nanotubes and etched foil by convex portions become them to pressurize a bent state under pressure to said convex portion biting into the carbon nanotubes And then peeling the substrate from the etching foil. A method for producing an electrode for an electric double layer capacitor, comprising: Prior to the integration, the surface of at least the collector side of the sheet or substrate, an electric double layer capacitor according to any one of claims 1 1 to claim 1 3, characterized in that sputtering of aluminum For manufacturing an electrode. Pressing pressure to integrate with the carbon nanotube and the etching foil, 0.01~100t / wherein the cm is ² claims 1 1 to an electric double layer according to any one of claims 1 4 A method for manufacturing a capacitor electrode.