WO2003077333A1

WO2003077333A1 - Power storing element-use electrode, power storing element, power storing method

Info

Publication number: WO2003077333A1
Application number: PCT/JP2003/002776
Authority: WO
Inventors: Akira Fujishima; Mikiko Yoshimura; Kensuke Honda
Original assignee: Akira Fujishima; Mikiko Yoshimura; Kensuke Honda
Priority date: 2002-03-08
Filing date: 2003-03-10
Publication date: 2003-09-18
Also published as: JP2005293850A; AU2003211869A1

Abstract

A negative electrode having both functions as a secondary battery and an electric double-layer capacitor, and permitting free settings of an output density and an energy density. The electrode comprises a conductive substrate, and a conductive material carried on the surface of the conductive substrate and having a gap allowing the intercalation of cations in an electrolyte and a gap allowing contact between the conductive substrate and the electrolyte, wherein no intercalation of cations occurs in the conductive substrate to allow charges to be stored even if a negative voltage that causes the intercalation of cations in the conductive material is applied to the electrode in the electrolyte.

Description

Description Electrode for power storage unit, power storage unit, and power storage method

[Background of the Invention]

Field of the invention

The present invention relates to a negative electrode for a power storage having both functions as a secondary battery and an electric double layer capacity, a power storage using the same, and a power storage method.

Profile technology

Lithium-ion secondary batteries are charged and discharged by the movement of lithium ions between the positive and negative electrodes, causing lithium ions to be charged and discharged at both electrodes. Next battery. Such a lithium ion secondary battery has advantages such as high energy density, long life, and high voltage. Graphite, amorphous carbon, metal oxides, metal sulfides, and the like are known as negative electrode materials for lithium ion secondary batteries.

In recent years, it has been reported that carbon nanotubes (CNT), which are attracting attention as a new material, are capable of lithium ion (Li ⁺ ) incorporation between tube and tube layers. The carbon nanotube interlayer is 3.4A, which is larger than the graphite interlayer (3.35A), but the carbon nanotube is a closed layer, Li + is hard to enter, and it has been thought that the hysteresis of charge / discharge becomes large. However, in recent years, it has been reported that lithium ion incineration progresses not only between interlayers but also between voids formed by carbon nanotubes, exceeding the theoretical capacity of graphite (372 mA hg ¹ ). It has been reported that high capacity is developed.

Japanese Patent Application Laid-Open No. 5-266690 discloses a lithium secondary battery having an improved initial capacity, using a carbon nanotube formed with a rubber-based adhesive as a negative electrode.

Electric double-layer capacitors have attracted attention in recent years as large-capacity and excellent small backup power supplies, replacing conventional battery power supplies. In the electric double layer capacity, the movement of electrolyte ions in the solution and the desorption on the electrode surface only occur with charge and discharge. This is different from a secondary battery that involves a chemical reaction. Activated carbon, polyacene, and other porous carbon materials are used as the negative electrode material for the electric double layer capacity. By the way, conventionally, when a porous carbon material such as activated carbon and polyacene is allowed to function as an electric double layer capacity, an electrolyte solution containing no lithium ions has been used. On the other hand, conventionally, when these porous carbon materials are used for a lithium ion secondary battery, a lithium ion-containing electrolyte is used. In other words, it was difficult for conventional porous carbon materials to simultaneously exhibit the function as an electric double layer capacity and the function as a lithium ion secondary battery in a common electrolyte called lithium ion-containing electrolyte. .

Diamond is inherently the resistivity is an insulating material of about ¹ 0 1 ³ Ω cm, obtaining conductivity by de one-flop traces impure product. This conductive diamond is expected to have various uses. One of them is utilization as an electrode for electrochemical use. When conductive diamond is viewed as an electrode for electrochemical use, it has the excellent features of having a wide potential window and extremely low background current. In addition, it is physically and chemically stable and has excellent durability. Electrodes having a conductive diamond (preferably a thin film thereof) have been commonly referred to as diamond electrodes.

Pioneering work on diamond electrodes was performed by Iwaki et al. (Iwaki et al., Nuclear Instruments and Methods, 209-210, 1129 (1983)). They studied the properties of single-crystal diamond with surface conductivity imparted by implanting argon-nitrogen ions as an electrically conductive material. At the same time, a cyclic voltammogram in the electrolyte solution was also shown. Subsequently, the characteristics of polycrystalline diamond electrodes synthesized by gas phase using hot filament have been reported (Pleskov et al., J. Electroanal. Chem., 228, 19 (1993)).

Some of the present inventors have previously reported the reduction of nitrogen oxides using a diamond electrode synthesized in a gas phase (Tenne et al., J. Electroanal. Chem., 347, 409 (1993)). In this study, a p-type semiconductor diamond doped with boron as a dopant was used as the electrode. Then, as a diamond electrode, a p-type semiconductor using boron as a dopant or a more conductive metal-like conductive diamond Usage has become mainstream. In the 1990s, diamond electrode research was conducted by several groups, and from 1995 onwards, plasma electrodeposition (PCVD) equipment was used to obtain larger diamond thin films. Research on diamond electrodes has also been seen in the electrochemical field.

[Summary of the Invention]

The present inventors have now found that a certain type of electrode can simultaneously function not only as a negative electrode of a secondary battery but also as an electric double layer capacity in the same electrolytic solution. More specifically, by constructing a secondary battery system using a carbon nanotube grown on a conductive diamond substrate as the negative electrode, it not only functions as the negative electrode of the secondary battery, but also the electric double layer capacity. It was found that the function of evening can be expressed simultaneously in the same electrolyte. We also found that the output density and energy density of the system can be arbitrarily set by changing the amount of carbon nanotubes supported. The present invention is based on these findings.

Therefore, the present invention provides a negative electrode for a power storage, which has both functions as a secondary battery and an electric double layer capacity, and whose output density and energy density can be arbitrarily set, and a power storage using the same. Its purpose is to provide power storage methods.

And the electrode for power storage according to the present invention,

A conductive substrate;

A gap which is supported on the surface of the conductive substrate and allows for the incorporation of cations in the electrolyte and a gap which allows contact between the conductive substrate and the electrolyte. Having a conductive material having

In the electrolytic solution, even when a negative voltage that causes the cation of the cation to be applied to the conductive material is applied to the electrode, the conductive substrate has a positive ion. The electric charge is accumulated without causing the evening curling. In addition, the pork storage according to the present invention comprises:

Said electrode as a negative electrode,

With the counter electrode as the positive electrode An electrolyte in which the negative electrode and the positive electrode are immersed;

Is provided.

Further, the power storage method according to the present invention includes:

Prepare the above electrode as a negative electrode and a counter electrode as a positive electrode,

Immersing the electrode and the counter electrode in an electrolytic solution,

On the negative electrode, the conductive material generates an in-charge of cations in an electrolytic solution, but the conductive base material does not generate an in-charge of cations. Applying a negative voltage

Comprising.

[Brief description of drawings]

FIG. 1 is a sectional view showing an example of the electrode of the present invention.

FIG. 2 is a cross-sectional view showing another example of the electrode of the present invention.

FIG. 3 is a cross-sectional view illustrating an example of the power storage unit of the present invention.

FIG. 4 is a scanning electron microscope (SEM) image of the surface of Sample 1 obtained in Example 1.

FIG. 5 is a cyclic voltammogram measured for samples 1 to 3 in Example 2.

FIG. 6 is a diagram showing the relationship between the output density and the energy density measured for samples 1 to 4 in Example 3.

FIG. 7 shows the relationship between the number of cycles and the discharge capacity measured for Sample 1 in Example 4.

[Specific description of the invention]

Electrodes for power storage

FIG. 1 shows an example of the electrode of the present invention. The electrode 1 according to the present invention includes a conductive substrate 2 and a conductive substance 3. A conductive wire 4 is connected to the conductive base material 2 so as to be electrically connectable. The conductive material 3 is carried on the surface of the conductive substrate 2. Conductive substance 3 is a lithium ion or other positive ion It has a possible gap, and by applying a negative voltage exceeding a certain level to the electrodes, the cations are accumulated in the gap by the in-situ curation. Thus, it functions as the negative electrode of the secondary battery. At this time, there is no generation of cation in the conductive substrate 2. The conductive base material 2 does not originally have a gap in which cations can be subjected to in-situ curing, or even if it has such a gap, no in-situ radiation occurs under the above-mentioned applied voltage. The conductive substance 3 is supported on the conductive substrate 2 so as to have a gap that allows contact between the conductive substrate 2 and the electrolytic solution. Therefore, the electrolyte ions in the electrolyte move and are arranged on the surface of the conductive substrate 2 to form a so-called electric double layer, and as a result, it also has a function as an electric double layer capacity.

As described above, the negative electrode for a power storage device of the present invention exhibits its function as a secondary battery and an electric double layer capacitor. The function as an electric double layer capacity by the conductive base material is considered to contribute particularly to the improvement of the power density of the power storage unit. In addition, the function as a secondary battery using a conductive substance is considered to particularly contribute to the improvement of the energy density of the power storage device. Therefore, by changing the amount of the conductive substance carried on the conductive substrate, the output density and the energy density of the power storage device can be freely set according to the application. That is, when the energy density is more important than the output density, the amount of the conductive substance carried on the conductive substrate can be increased, and more cations can be accumulated in the conductive substance. On the other hand, when the output density is more important than the energy density, the amount of the conductive substance carried on the conductive substrate is reduced, and the gap for ensuring the contact between the conductive substrate and the electrolyte is increased. As a result, more charges can be stored in the conductive substrate. In the present invention, the conductive base material has conductivity, and even if a negative voltage that causes in-situ curation of a cation such as lithium ion in the conductive material is applied to the electrode, the conductive base material may be a cation. The one which does not cause the above-mentioned currencies can be used. Preferred examples of the conductive substrate include conductive diamond, glassy carbon, conductive diamond-like carbon, and conductive amorphous carbon. According to a preferred embodiment of the present invention, conductive diamond is used as the conductive substrate. Diamond is inherently a good insulator. However, by adding a Group 3 or Group 5 impurity, the semiconductor or metal becomes conductive. In the present invention, diamond exhibiting semiconductor-metal-like conductivity is used as an electrode. Conductive diamond is a material that has a wide potential window with respect to other carbon and metal electrodes and exhibits a small residual current density, and has the advantage that lithium ion incineration does not progress.

In the present invention, the diamond electrode described in JP-A-2001-21521 can be used. The details are as follows.

Substances added to impart conductivity to diamond include Group 3 and 5 elements as described above, more preferably boron, nitrogen, and phosphorus, and most preferably boron or nitrogen. . Amount of substance to be added pressure to impart the conductivity, may be suitably determined within the range that can impart conductivity to diamond, for example, 1 X 10- ² ~ 10_ about ⁶ Omega cm conductivity Is preferably added in such an amount that gives Generally, the amount of the substance added to impart this conductivity is controlled by the amount added in the conductive diamond manufacturing process.

According to a preferred embodiment of the present invention, it is preferable that a conductive diamond thin film is formed on a support, and a conductive wire is further connected to the conductive diamond thin film to form a conductive substrate. As the support, S i (e.g., single crystal silicon), Mo, W, Nb, T i, F e, Au, N i, C o, A 1 2 0 3, S i C ;, S i 3 N _{_{4, Z r 0 2, MgO}} , graphite, single crystal diamond, cBN, quartz glass and the like, in particular monocrystalline silicon, Mo, W, Nb, T i, the use of S i C ;, single crystal diamond good Good.

The thickness of the conductive diamond thin film is not particularly limited, but is preferably about l to 100 m, more preferably about 5 to 50 // m.

According to a preferred embodiment of the present invention, the conductive diamond thin film is preferably produced by a chemical vapor deposition method. Chemical vapor deposition is a method of synthesizing a substance by chemically reacting gaseous raw materials in the gas phase, and is similar to CVD (Chemical Vapor Deposition). Commonly called. This method is widely used in the semiconductor manufacturing process, and can be used for the production of the conductive diamond thin film of the present invention with appropriate modification.

Chemical vapor synthesis of diamond is performed by using a mixture of hydrogen and a carbon-containing gas such as methane as a raw material gas, exciting it with an excitation source, supplying it to a support, and depositing it.

Excitation sources include hot filament, microwave, high frequency, DC glow discharge, DC arc discharge, and combustion flame. It is also possible to adjust the nucleation density by combining a plurality of them, and to enlarge and uniform the area.

As a raw material, many types that contain a carbon, decomposition by the excitation source is excited, C, activated carbon, such as C _2, and CH, such as _{_{_{CH 2, CH 3, C 2}}} H 2 Compounds that generate hydrocarbon radicals are available. Preferable specific examples include CH ₄ , C 2 H 2, C 2 H ₄ , CioHi ₆ CO, CF ₄ as a gas, CH ₃ OH, C ₂ H 5 OHS (CH ₃ ) ₂ CO as a liquid, and graphite and fullerene as a solid.

In the gas phase synthesis method, the addition of a substance that imparts conductivity to diamond is performed, for example, by placing a disk of the added substance in the system, exciting it in the same way as the carbon source material, and introducing the added substance into the carbon gas phase. The method can be carried out by adding an additive substance to a carbon source in advance, introducing the additive substance into the system together with the carbon source, exciting with an excitation source, and introducing the additive substance into the carbon gas phase. According to a preferred embodiment of the present invention, the latter method is preferred. Especially, when using acetone, a liquid such as methanol as a carbon source, a method of dissolving the boron oxide (B ₂ 0 ₃₎ and boron source thereto, it is easy to control the concentration of boron, which is either One convenient This is preferred. For example, in the case of adding boron to a carbon source in a gas phase synthesis method, the amount is generally about 10 to 12,000 ppm, and preferably about 1,000 to about L ppm.

According to a preferred embodiment of the present invention, the production of the conductive diamond thin film is preferably performed by a plasma chemical vapor deposition method. This plasma-enhanced chemical vapor synthesis method has the advantage that the activation energy for causing a chemical reaction is large and the reaction is fast. In addition, this method produces chemical species that do not exist at high thermodynamic temperatures. Thus, a reaction at a low temperature becomes possible. Several reports have already been made on the production of conductive diamond thin films by the plasma chemical vapor deposition method, including some of the present inventors (see, for example, Yano et al., J. Electrochem. Soc., 145 (1998). 1870), it is preferable to carry out according to the method described in these reports.

According to a preferred embodiment of the present invention, it is preferable that the conductive substrate is porous at least on its surface. When the substrate surface is porous, its specific surface area increases. Therefore, more charges can be collected, and as a result, the electric double layer capacity increases and the dischargeable time becomes longer. It is also considered that the marginal dischargeable current increases and the marginal output increases.

According to a preferred embodiment of the present invention, it is preferable that the surface of the base material be made porous by forming pores having the same arrangement as the mask by plasma etching using anodized alumina as a mask. According to this method, it is possible to obtain a conductive substrate in which pores are regularly formed in a honeycomb shape. Such a processing method can be performed, for example, based on the method disclosed in JP-A-2000-13993.

The electrode of this embodiment is shown in FIG. FIG. 2 is a sectional view of the electrode 11 of this embodiment. As shown in FIG. 2, the electrode 11 has a conductive substance 13 supported on a conductive base material 12 in which pores are regularly formed in a honeycomb shape. The conductive material 13 is formed regardless of the inside and outside of the pore, but the conductive material 13 can be supported only in the pore. A conductive wire 14 is connected to the conductive base material 12 via a coating, and is electrically connectable.

Further, according to another preferred embodiment of the present invention, a porous support can be coated with a conductive diamond or the like to form a conductive substrate having a porous surface. Preferred examples of the porous support in this case include a tungsten mesh, a molybdenum mesh, and a silicon substrate having a surface provided with pores.

Further, according to another preferred embodiment of the present invention, the conductive base material includes a conductive diamond powder and a binder, so that the conductive base material surface is made porous. preferable. Binders that can be used in the present invention include conductive diamond on a support without substantially affecting the electrical properties of the conductive diamond. The resin is not limited as long as it can be fixed and molded. Preferred examples include resin, and specific examples thereof include Nafion 66 (manufactured by DuPont), Nafion 77 (manufactured by DuPont), and Teflon 7 J (manufactured by DuPont) and the like. The preferable addition amount of the binder is 30% by weight or less, more preferably 20% by weight or less, and further preferably 5 to 15% by weight based on the whole conductive substrate. The conductive diamond powder has a preferable mass average particle diameter of 1 to 1000 nm, more preferably 5 to 50 Onm, and further preferably 10 to 10 Onm. The conductive electrode according to the above preferred embodiment can be obtained as a paste-like solid by kneading conductive diamond powder with a binder, for example.

According to a preferred embodiment of the present invention, the pore diameter on the porous substrate surface is preferably lnm-100 Onm, more preferably 400-50 Onm. The depth of the pores is preferably 1 to 5 m, more preferably 1 to 2 / m. The preferred interval between the holes is 1.2 nm to 12 ° 0 nm, more preferably 100 ηπ! ~ 500 nm. The conductive material in the present invention has conductivity, and ensures a gap capable of intercalating cations such as lithium ions in the electrolytic solution and a contact between the conductive substrate and the electrolytic solution. Can be used. Preferred examples of the conductive material include carbon nanotubes, graphite, activated carbon, carbon fiber, mesocarbon microbeads, and the like.

According to a preferred embodiment of the present invention, a carbon nanotube is used as the conductive substance. Carbon nanotubes are seamless coaxial cylinders of hexagonal mesh sheets of carbon atoms, and their diameters are on the order of nanometers, ranging from 1 to 50 nm. Carbon nanotubes produce lithium ion incursion at a constant negative voltage. It is thought that this intercalation occurs not only between the carbon nanotube layers but also in the voids formed by the carbon nanotubes. Therefore, according to this carbon nanotube, a high capacity far exceeding the theoretical capacity between the graphite layers (C ₆ Li; 372 mAhg ¹ ) can be realized. In addition, since carbon nanotubes have a cylindrical structure, a certain amount of Even if it is supported in a large amount, a sufficient gap can be provided on the surface of the conductive substrate for ensuring contact with the electrolytic solution. Therefore, the secondary battery function by the carbon nanotube can be exhibited while securing the electric double layer capacity function of the conductive base material.

The loading of carbon nanotubes on the conductive substrate can be carried out according to a known method, and is described in G. Che, BB Lakshmi, C. R. Martin, and ER Fisher, Chem. Mater., 10 (1998) 260 , And S. Huang, L. Dai, and AWH Mau, J. Phys.

Chem. B, 103 (1999) 4223 and the like. For example, it can be carried out by using iron fine particles as a catalyst and growing by phtalocyanine as a carbon source by gas phase synthesis. For example, to support iron fine particles on a conductive diamond substrate, the substrate is immersed in an iron nitrate solution to adhere the iron particles, and thermally reduced in a hydrogen atmosphere (eg, 580 ° C). C). Gas phase synthesis can be performed by decomposing phthalocyanine into carbon atoms at a temperature of about 900 ° C. and growing carbon nanotubes from fine iron particles on a conductive diamond substrate.

In the present invention, the amount of the conductive substance to be carried can be appropriately determined according to the output density and the energy density required for power storage applications. That is, when the energy density is more important than the output density, the amount of the conductive substance carried on the conductive substrate can be increased, and more cations can be accumulated in the conductive substance. On the other hand, when the output density is more important than the energy density, the amount of the conductive substance carried on the conductive substrate is reduced, and the gap for ensuring the contact between the conductive substrate and the electrolyte is increased. As a result, more charges can be stored in the conductive base material.

Power storage unit and power storage method

The power storage body used in the power storage method of the present invention may have a configuration of a general lithium ion secondary battery except that the electrode of the present invention is used as a negative electrode. That is, in the method according to the present invention, an electrode of the present invention as a negative electrode and a counter electrode as a positive electrode are prepared, and these electrodes are immersed in an electrolytic solution. Of the cation, but the conductive substrate has a cation Apply no negative voltage to the negative electrode. It is preferable to select such a voltage by considering the result of the cyclic voltammogram measurement of the negative electrode. Figure 3 shows a schematic representation of this system. That is, the power storage unit 21 according to the present invention includes the electrode 22 of the present invention as a negative electrode, the counter electrode 23 as a positive electrode, and an electrolytic solution 24 in which the negative electrode and the positive electrode are immersed.

The electrolytic solution used in the present invention comprises an electrolyte containing a cation capable of being converted into a conductive substance. Preferred cations are lithium ions, preferred examples of the electrolyte in the case of this, lithium perchlorate (L i C 1 0, L i CF 3 SOKL i PFL i A s F 6 , and the like. The present invention The solvent of the electrolytic solution used in the method may be any of an aqueous solvent and a non-aqueous solvent, but it is preferable to use a non-aqueous organic solvent. Solvents have a wider potential window than aqueous solvents, which can significantly improve both power density and energy density Examples of non-aqueous solvents include tetrahydrofuran, ethylene carbonate, propylene carbonate, oxolane, lactone lactone, and acetonitrile. And amide solvents such as dimethylformamide, and propylene carbonate. Masui.

According to a preferred embodiment of the present invention, it is preferable that a liquid in which lithium perchlorate is dissolved in propylene power is used as the electrolytic solution.

Preferable examples of the counter electrode (positive electrode) in the present invention include cobalt / nickel oxide, manganese oxide, transition metal oxide, and transition metal sulfide.

[Example]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples.

Example 1: Making electrodes

According to a known method, a diamond thin film in which boron is introduced at a high concentration (10,000 ppm, B / C ratio) is deposited on a conductive n-type silicon (111) surface by a microwave plasma CVD apparatus. (ASTeX Corp., Wobum, MA). Obtained da The surface of the diamond thin film was polished to a surface roughness of 1 nm or less. The surface of the diamond thin film was masked with anodized alumina, and holes were formed in a honeycomb shape by oxygen plasma etching. Anodized alumina was produced by holding the aluminum plate after electropolishing at a constant potential of 195 V in 0.5 M phosphoric acid for 5 minutes. Oxygen plasma etching was performed using a plasma etching apparatus (SAMC0, BP-1) at an oxygen pressure of 20 Pa and an output of 150 W for 30 minutes.

The resulting diamond film to _{_{24.8 mM Fe (N0 3) 3}} (Wako Pure Chemical Industr ies, Ltd.) and impregnated overnight I ethanol solution was deposited iron particles. This diamond thin film was placed downstream of an electric furnace (Ohkurariken Co., Ltd.), and phthalocyanine (Aldrich) as a carbon source was placed upstream of the electric furnace. In this electric furnace, under a hydrogen atmosphere (Takachiho Co., Ltd., 99.99 I, 30 _ra ), it is heated at 580 ° C for 3 hours to thermally reduce iron ions on the diamond thin film to fine iron particles. I let it. Then, argon (Takachiho Co., Ltd., 99.95% 21 _sra ) was added into the electric furnace. By heating the electric furnace and its upstream at 900 ° C for 2 hours, carbon nanotubes were grown on iron fine particles by gas phase synthesis. Thus, Sample 1 in which carbon nanotubes were supported on a conductive diamond thin film was obtained.

A sample 2 was obtained in the same manner as the sample 1 except that the surface polishing and the oxygen plasma etching were not performed.

For comparison, an untreated diamond thin film that had not been subjected to surface polishing, oxygen plasma etching, and carbon nanotube formation was used as Sample 3.

For comparison, Sample 4 was obtained in the same manner as in Sample 1, except that no carbon nanotube was formed.

The surface of the obtained sample 1 was observed using a scanning electron microscope (SEM, JE0L Model JSM-5400 LV). The result was as shown in FIG.

Example 2: Measuring cyclic voltammograms

For the samples 1 to 3 obtained in Example 1, cyclic voltammograms were measured using a potentiometer (Hokuto Denko Research, model HZ-3000). Cyclic voltammograms were measured under the following conditions. Potential scanning speed: 0.3 mV s " ¹

Measurement temperature: room temperature

Working electrode: Samples 1-3 (fixed to the bottom of the glass cell using the 0 ring as a joint)

Counter electrode: Glassy force-bon electrode

Reference electrode: Ag / Ag ⁺ (BAS Co., Ltd.)

Non-aqueous electrolyte: 1 M LiC10 ₍ / PC (Kishida Chemistry Co., Ltd.)

Glass containers such as cells and flasks used in the above measurements were washed with Milli-Q water (Millipore) and dried overnight in a dryer before use.

The results obtained were as shown in FIG. As shown in FIG. 5, in sample 3 in which carbon nanotubes were not supported, lithium indium was charged at a potential of _3.3 to -0.2 V (vs. Ag / Ag +). No reduction current due to curry was observed. On the other hand, in Sample 2 in which a carbon nanotube was carried on an unprocessed diamond electrode, a reduction current due to lithium in-carnation was confirmed. Furthermore, in Sample 1 in which carbon nanotubes are supported on a honeycomb-processed diamond electrode, the reduction current due to lithium incineration is increased to about twice that in Sample 2. Was confirmed.

Example 3: Power density and energy density measurement

The constant current discharge characteristics of the samples 1 to 4 obtained in Example 1 were measured using a potentiometer (Hokuto Denko Research, model HZ-3000). This measurement was performed under the following conditions.

Measurement temperature: room temperature

Counter electrode: Glass electrode

Reference electrode: Ag / Ag ⁺ (BAS Co., Ltd.)

Non-aqueous electrolyte: 1 M LiC10 ₍ / PC (Kishida Chemistry Co., Ltd.)

The glass containers such as cells and flasks used in the above measurements were washed with Milli-Q water (Mil lipore) and then dried overnight in a dryer before use. From the results of the obtained discharge characteristics, the output P a »e and the energy density E are calculated using P.» E = average (V) * I and E = ∑ (V * I * Δt) "

The results obtained were as shown in FIG. As shown in Fig. 6, it was confirmed that Samples 1 and 2 carrying carbon nanotubes had significantly higher energy density and power density than Samples 3 and 4 not carrying carbon nanotubes. . Sample 1 in which carbon nanotubes are supported on a honeycomb-processed diamond electrode has a two-fold increase in output and 4.9 times higher than Sample 2 in which carbon nanotubes are supported on an unprocessed diamond electrode. A two-fold increase in energy density was observed.

Example 4: Durability test by continuous use

Using sample 1, a constant current charge / discharge cycle was performed at a charge current of 24 / A and a discharge current of 24A, and the transition of dischargeable capacity with respect to the number of cycles was observed. The results obtained were as shown in FIG. In Fig. 7, the horizontal axis is the number of cycles (1 cycle: about 4 hours, 6 cycles per day are possible), and the vertical axis is the dischargeable capacity. The following can be seen from these results. In other words, after the start of discharge, the dischargeable capacity increased until about 10 cycles, and thereafter maintained a constant value of about 89.4 mA hg- ¹ . The increase in capacity immediately after the start of discharge is considered familiar to the electrolyte of the electrode. No electrode deterioration was observed in the measurement up to 85 cycles (corresponding to 2 hours during continuous measurement). Therefore, it was confirmed that an electrode having excellent durability for continuous use and high reliability for long-term operation was obtained.

Claims

The scope of the claims

1. An electrode for a power storage body,

A conductive substrate;

A gap which is supported on the surface of the conductive base material and allows the cations in the electrolytic solution to be absorbed and a gap which enables the conductive base material to come into contact with the electrolytic solution are formed. Having a conductive material having

In the electrolytic solution, even when a negative voltage that causes in-situ cation of the cation to the conductive material is applied to the electrode, the conductive base material is applied to the conductive substrate. An electrode where charge is stored without curtailment.

2. The electrode according to claim 1, wherein the conductive substrate is selected from the group consisting of conductive diamond, glassy carbon, conductive diamond-like carbon, and conductive amorphous carbon.

3. The electrode according to claim 1, wherein the conductive substrate is a conductive diamond.

4. The method according to any one of claims 1 to 3, wherein the conductive substance is selected from the group consisting of carbon nanotubes, graphite, activated carbon, carbon fiber, and meso-carbon microbeads. Electrodes.

5. The electrode according to any one of claims 1 to 3, wherein the conductive substance is a carbon nanotube.

6. The electrode according to any one of claims 1 to 5, wherein the cation in the electrolyte is a lithium ion.

7. The electrode according to claim 1, wherein the conductive substrate is a conductive diamond, the conductive substance is a carbon nanotube, and a cation in the electrolyte is a lithium ion.

8. The electrode according to any one of claims 1 to 7, wherein the conductive substrate has a porous surface.

9. The electrode according to claim 8, wherein the conductive material is carried at least in pores of the porous surface.

10. The conductive base material includes a conductive diamond powder and a binder. The electrode according to claim 8, wherein the electrode comprises:

11. The electrode according to any one of claims 1 to 10 as a negative electrode, and a counter electrode as a positive electrode.

An electrolyte in which the negative electrode and the positive electrode are immersed;

A power store comprising: ,

12. The electrolyte is a _{L i C IO Li CF 3 S0} 3, L iPF 5, and a solution prepared by dissolving one or more electrolytes in a non-aqueous solvent selected from the group consisting of Li A s, claim 11. The power storage device according to item 1.

13. The electric power according to claim 12, wherein the non-aqueous solvent is at least one selected from the group consisting of tetrahydrofuran, ethylene carbonate, propylene carbonate, oxolane, ptirolactone, nitrile solvent and amide solvent. Storage.

14. The power storage unit according to claim 11, wherein the electrolyte is a solution of lithium perchlorate in propylene carbonate.

15. Prepare an electrode according to any one of claims 1 to 10 as a negative electrode, and a counter electrode as a positive electrode,

Immersing the electrode and the counter electrode in an electrolytic solution,

On the negative electrode, the conductive material causes cation migration in the electrolytic solution, but the conductive base material does not generate cation migration. , Applying a negative voltage

A power storage method.

16. Conductive diamond with carbon nanotubes supported on its surface.

17. The conductive diamond according to claim 16, wherein the conductive diamond has a porous surface.

18. The conductive diamond according to claim 16, wherein the carbon nanotube is supported on at least the pores of the porous surface.