JP2014130980A - Method of manufacturing cobalt nanostructure and capacitor using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of manufacturing a capacitor which allow for high energy and high output.SOLUTION: In a method of manufacturing a capacitor, a pair of electrodes are immersed in an electrolyte containing a cobalt complex, a cobalt nano structure is precipitated on one of the pair of electrodes by electrolysis of the electrolyte in a magnetic field, and then the electrode on which the cobalt nano structure is precipitated is arranged to face a counter electrode via the electrolyte layer for capacitor. The structure is further miniaturized by MHD effect and micro MHD effect, by applying a magnetic field when precipitating the cobalt nano structure, and the actual surface area can be increased and high speed ion transport can be realized.

Description

  The present invention relates to a method for producing a cobalt nanostructure and a capacitor using the same. More specifically, the present invention relates to a method for producing a cobalt nanostructure by electrolysis in a magnetic field and an electrochemical capacitor using the same.

  In recent years, efforts for environmental problems have become important, and there has been a demand for an efficient power source with a lighter burden on the environment. One technology that is expected to contribute to this demand is an electrochemical capacitor. The electrochemical capacitor is a device for accumulating and outputting electric charges by using an electrochemical action, and representative examples include an electrochemical double layer capacitor and a redox capacitor.

  The electrochemical double layer capacitor has a pair of electrodes and an electrolyte disposed between the pair of electrodes, and is formed by adsorption (non-Faraday reaction) of ions generated at the interface between the electrolyte and the electrodes. It is a capacitor that can store electric charge by using a carbon material that has a very large specific surface area as an electrode, and can be increased in capacity, such as an auxiliary power source for vehicles such as buses and trucks, It has been used as a power source for mobile devices such as smartphones.

  On the other hand, a redox capacitor is a capacitor capable of accumulating charges by using a pseudo-capacitance expressed by a plurality of continuous redox (oxidation-reduction) reactions of an active material, and has a larger capacity than the above electric double layer capacitor. In addition, there is an advantage that the instantaneous charge / discharge characteristics are superior to those of the battery, which is expected more.

  As a known technique related to an electrochemical capacitor, for example, in Patent Document 1 below, an electrochemical having a pair of electrodes having a cobalt nanostructure formed at least on one side and an electrolyte filled between the pair of electrodes. A capacitor is disclosed.

JP 2009-200449 A

  Certainly, the technique described in Patent Document 1 is considered to be a useful technique for realizing a high energy and high output electrochemical capacitor.

  However, there is no upper limit for increasing the energy and output of the capacitor, and it is very important to further increase the energy and output.

  Then, in view of the above, an object of the present invention is to provide a method for manufacturing a cobalt nanostructure capable of achieving higher energy and higher output, and a capacitor using the cobalt nanostructure.

  The inventors of the present invention have been diligently studying the above problems. When a magnetic field is applied when depositing a cobalt nanostructure, the structure is refined by the MHD effect and the micro MHD effect, the actual surface area is large, and fast ions are formed. Cobalt nanostructures having nanostructures that can be transported have been created, and it has been found that electrical characteristics can be greatly improved, and the present invention has been completed. Here, the “MHD effect” is an effect in which when a magnetic field is applied parallel to the electrode surface during the electrolytic deposition of the structure, a vortex-like convection is caused on the electrode surface and the form of the deposited structure is changed. “Micro MHD effect” means that by applying a magnetic field perpendicular to the electrode surface, several small vortex-like convections are generated in a minute region of the electrode surface, and the structure of the deposit The effect that changes.

  That is, in the method for producing a cobalt nanostructure according to the first aspect of the present invention, a pair of electrodes is immersed in an electrolytic solution containing a cobalt complex, and the electrolytic solution is electrolyzed in a magnetic field to one of the pair of electrodes. Cobalt nanostructures are deposited.

  In addition, a capacitor according to another aspect of the present invention is obtained by immersing a pair of electrodes in a material electrolyte containing a cobalt complex, electrolyzing the electrolyte in a magnetic field, and placing a cobalt nanostructure on one of the pair of electrodes. It is manufactured by depositing and disposing the electrode on which the cobalt nanostructure is deposited facing the counter electrode via the capacitor electrolyte layer.

  A capacitor according to another aspect of the present invention is such that an electrode on which oriented cobalt nanostructures are arranged is arranged to face a counter electrode through an electrolyte layer for a capacitor.

  As described above, according to the present invention, it is possible to provide a method for producing a cobalt nanostructure capable of achieving higher energy and higher output, and a capacitor using the cobalt nanostructure.

It is a figure which shows the outline of the process of the manufacturing method of the capacitor which concerns on embodiment. It is a figure showing the outline of the section of the capacitor concerning an embodiment. It is a figure which shows the outline of the apparatus used in the electrolysis which concerns on an Example. It is a figure which shows the result of the cyclic voltammetry of the example using the electrode which concerns on an Example. It is a figure which shows the result of the cyclic voltammetry of the example using the electrode which concerns on an Example. It is a figure which shows the result of the charging / discharging characteristic of the example using the electrode which concerns on an Example. It is a figure which shows the result of the charging / discharging characteristic of the example using the electrode which concerns on an Example. It is a figure which shows the result of the charging / discharging characteristic of the example using the electrode which concerns on an Example. It is a figure which shows the result of the charging / discharging characteristic of the example using the electrode which concerns on an Example. It is a figure which shows the dependence with respect to the electricity supply of the specific capacity Cm of the example using the electrode which concerns on an Example. It is a figure which shows the dependence with respect to the electricity supply of the specific capacity Cm of the example using the electrode which concerns on an Example. It is a figure which shows the dependence with respect to the electricity supply of the specific capacity Cm of the example using the electrode which concerns on an Example. It is a figure which shows the roughness factor of the example using the electrode which concerns on an Example. It is a figure which shows the roughness factor of the example using the electrode which concerns on an Example. It is a figure which shows the example of the SEM image of the electrode which concerns on an Example. It is a figure which shows the example of the SEM image of the electrode which concerns on an Example. It is a figure which shows the example of the SEM image of the electrode which concerns on an Example. It is a figure which shows the example of the SEM image of the electrode which concerns on an Example. It is a figure which shows the example of the SEM image of the electrode which concerns on an Example.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. However, the present invention can be implemented in many different forms, and is not limited to the following embodiments and examples.

  FIG. 1 is a diagram showing an outline of the steps of a method for manufacturing a capacitor (hereinafter referred to as “the present capacitor”) according to the present embodiment (hereinafter referred to as “the present method”). As shown in the figure, this method is (1) immersing a pair of electrodes in an electrolytic solution containing a cobalt complex, electrolyzing the electrolytic solution in a magnetic field, and depositing cobalt nanostructures on one of the pair of electrodes. And (2) a step (S2) in which the electrode on which the cobalt nanostructure is deposited is disposed to face the counter electrode via the capacitor electrolyte layer.

  The step of (1) immersing a pair of electrodes in an electrolytic solution containing a cobalt complex and electrolyzing in a magnetic field to deposit a cobalt nanostructure on one of the pair of electrodes in the present method produces the cobalt nanostructure. This method is used as an electrode for a capacitor in this embodiment.

  The pair of electrodes in this step has conductivity and can hold cobalt nanostructures deposited from the electrolyte, and is not limited to this, but a conductive plate, An example is one in which a conductive film is disposed on an insulating plate.

  As an example of an electrode including a conductive plate, a metal plate and a carbon plate can be exemplified. Examples of the conductive film disposed on the insulating plate include ITO (indium tin oxide) and IZO (indium zinc oxide) on the insulating plate such as glass, polyester film, and polycarbonate film. Conductive films such as metal oxide films such as FTO (fluorine-doped tin oxide), ATO (aluminum-doped tin oxide) and GTO (gallium-doped tin oxide), and polymer films such as polyacetylene, polypyrrole, polythiophene and polyaniline What has been arranged can be exemplified. In addition, from the viewpoint of productivity, mechanical strength, price, and lightness, it is preferable that ITO is formed on a metal plate or a glass substrate. Note that the plate of the electrode may be flexible enough to be bent, and the volume can be reduced by bending the conductive film and the plate with flexibility.

  In this step, the electrolytic solution is a substance through which an electric current flows through ionic conduction, and includes, but is not limited to, at least a solvent, a cobalt complex, and a supporting electrolyte.

  As a solvent in the electrolytic solution of this step, while holding a cobalt complex and a supporting electrolyte, these can be dissociated into ions. It can be illustrated. In the case of an organic solvent, it is not limited as long as it can be electrolyzed, but acetonitrile, propylene carbonate, N-methylpyrrolidone, γ-butyrolactone, benzonitrile, methylene chloride, tetrahydrofuran / propylene carbonate, dimethylformamide, dimethyl sulfoxide, methanol Ethanol, and a mixed solvent of water and a solvent that dissolves in water among these solvents can be exemplified.

The cobalt complex in this step is not limited as long as it can be reduced by electrolysis and deposited as a cobalt nanostructure on the electrode. For example, hexaamminecobalt (III) chloride ([ Co (NH ₃ ) ₆ ] Cl ₃ ), pentaamminecobalt (III) chloride ([Co (NH ₃ ) ₅ Cl] Cl ₂ ), cobalt chloride (CoCl ₂ ), cobalt sulfate (CoSO ₄ ), and cobalt nitrate ( Co (NO ₃ ) ₃ ).

  The amount of the cobalt complex contained in the electrolytic solution in this step is not limited as long as the cobalt nanostructure can be deposited on the electrode, but is 0.001 weight per 100 weight parts of the solvent. Part to 50 parts by weight and more preferably 0.02 part to 10 parts by weight. When the amount is 0.001 part by weight or more, the actual electrode surface area can be increased by forming the nanostructure, and when the amount is 50 parts by weight or less, it is possible to suppress a decrease in the actual surface area due to the denseness of the nanostructure.

Further, the supporting electrolyte in this step is not limited as long as it does not prevent the electrolytic deposition of cobalt metal, but when the solvent is water, for example, LiCl, LiBr, Li ₂ SO ₄ , LiOH, LiClO ₄ , NaCl, NaBr, Na ₂ SO ₄ , NaOH, NaClO ₄ , KCl, KBr, K ₂ SO ₄ , KOH, KClO ₄ , and (C ₂ H ₅ ) ₄ NOH, (C ₂ H ₅ ) ₄ NCl, (C ₂ H ₅ ) ₄ NBr, (CH ₃ ) ₄ NOH, (CH ₃ ) ₄ NCl, (CH ₃ ) ₄ NBr, and their hydrates can be mentioned to form cobalt nanostructures with a large real surface area From this viewpoint, lithium sulfate monohydrate is more preferable. When the solvent is an organic solvent, for example, (C ₂ H ₅ ) ₄ NClO ₄ , (C ₂ H ₅ ) ₄ NF ₄ , (C ₂ H ₅ ) ₄ NPF ₆ , (C ₄ H ₉ ) ₄ NClO ₄ , (C ₄ H ₉ ) ₄ NF ₄ , (C ₄ H ₉ ) ₄ NPF ₆ , LiClO ₄ , NaClO ₄ , KClO ₄ , and (C ₄ H ₉ ) ₄ NOH. From the viewpoint that there is no possibility of adsorption to cobalt metal, LiClO ₄ , NaClO ₄ , and KClO ₄ are more preferable.

  The amount of the supporting electrolyte contained in the electrolyte in this step is not limited as long as the cobalt nanostructure can be deposited on the electrode, but when the weight of the solvent is 100 parts by weight, The amount is preferably 0.01 parts by weight or more and 300 parts by weight or less, and more preferably 0.1 parts by weight or more and 40 parts by weight or less. When the amount is 0.01 parts by weight or more, sufficient electric conduction of the electrolytic solution can be secured, and when the amount is 300 parts by weight or less, an excessive increase in the viscosity of the solution can be suppressed. The effect of not significantly lowering the ejection speed is exhibited.

In this step, the electrolysis is not limited as long as the cobalt complex can be electrolytically reduced to form a cobalt nanostructure on the electrode. It is preferable. Electrolytic reduction can be carried out either by electrolysis using a two-electrode cell using only two electrodes, or by electrolytic reduction using a three-electrode cell using a reference electrode. Therefore, it is preferable to use a three-electrode cell, and a two-electrode cell is preferable from the viewpoint of commercialization by mass production. In addition, when a three-electrode cell is used, the reference electrode can be any general-purpose reference electrode. For example, a saturated calomel electrode (SCE), a silver / silver chloride electrode, a standard hydrogen electrode (SHE) Etc. are preferably used. Further, as the potential at this time, for example, when SCE is used for the reference electrode, −0.5V to −2V is applied to the electrode.
vs. It is preferable to apply a potential of SCE, more preferably -0.8V to -1.5V.
vs. This is the potential range of SCE. The time for performing the electrolytic reduction is not limited, but it is preferably 0.1 seconds or longer and 10 hours or shorter, more preferably 1 second or longer and 1 hour or shorter, within the above desired electrolysis range. The temperature is not limited, but is preferably in the range of −10 ° C. to 100 ° C., more preferably 0 ° C. to 40 ° C.

Further, in this step, the energization amount of the electrolysis is preferably in the 0.01 C / cm ² or more 10.0c / cm ² or less, more preferably in the range of from in the range of less than 3.0C / cm ^2. 0.01 C / cm is effective such it is possible to have a practical charge and discharge capacity at ² or more to be, also that cause a decrease in the capacity by the 10.0c / cm ² or less structure The effect is that changes can be avoided. Moreover, there exists an effect that a structure which has big charging / discharging capacity | capacitance can be maintained by setting it as less than 3.0 C / cm < ² >.

  In this step, a pair of electrodes is immersed and electrolyzed in a magnetic field. By doing in this way, the cobalt nanostructure to precipitate can be made into the form which has a big real surface area and can perform high-speed ion transport. More specifically, compared to a structure formed without applying a magnetic field, a finer and more complicated cobalt nanostructure can be deposited.

  The magnetic field applied in this step may be a static magnetic field or an alternating magnetic field, but is preferably a static magnetic field from the viewpoint of promoting the fine structure of the cobalt nanostructure. When a static magnetic field is applied, for example, a permanent magnet is used, and the pair of electrodes can be easily arranged between the N pole and the S pole of the permanent magnet. In the case of an AC magnetic field, an AC magnet can be generated by using an electromagnet, specifically a coil made of a conductive wire, arranging a pair of electrodes inside the coil, and passing an AC current through the coil.

  The direction of the applied magnetic field is preferably substantially parallel or substantially perpendicular to the opposing surfaces of the pair of electrodes. The term “substantially parallel” as used herein includes, of course, being completely parallel, but includes the case where the orientation of the surfaces of the pair of electrodes facing each other is not completely parallel, An error range of about several degrees is included with respect to the direction, for example, an error of ± 5 degrees is included. Here, “substantially perpendicular” includes not only completely perpendicular, but also includes the direction of the surface of the electrode and the static magnetic field, including the case where the orientation of the surfaces of the pair of electrodes facing each other is not completely parallel. An error range of about several degrees is included, and an error of ± 5 degrees is included, for example.

  In this step, the magnetic field strength is preferably in the range of 1 mT to 100 mT, more preferably in the range of 5 mT to 1 T. By setting it to 1 mT or more, there is an effect that the nanostructure of the cobalt nanostructure can be expressed. By setting it to 10 T or less, the influence on the installation of the electrode substrate and the wiring due to the magnetic field strength being too large is achieved. There is an effect that the suppressed electrolysis operation becomes possible.

  In this step, cobalt nanostructures can be deposited on one of the pair of electrodes by the above treatment.

  In this embodiment, the cobalt nanostructure formed on the electrode is formed so that the actual electrode area can be expanded, and the cobalt nanostructure is limited as long as the electrode area can be expanded. Although not necessarily mentioned, cobalt nanowires, cobalt nanodendrites, porous cobalt, cobalt nano-microbeads and the like can be exemplified, and cobalt nanowires are preferable from the viewpoint of forming a larger actual surface area.

The amount of cobalt nanostructures deposited on the electrode in this step is not limited, but is preferably in the range of ² μg / cm ^{2 to} 2000 μg / cm ² . By making it 2 μg / cm ² or more, there is an effect that it becomes possible to have a practical charge / discharge capacity, and by making it 2000 μg / cm ² or less, avoiding structural changes that cause a decrease in capacity. There is an effect that can be done.

  In addition, the method includes the step of (2) preparing a counter electrode, disposing it facing the electrode on which the cobalt nanostructure is formed, and filling the capacitor electrolyte layer therebetween. In this step, a capacitor is specifically manufactured using the electrode manufactured in the step (1).

  First, a counter electrode is prepared. The counter electrode is paired with the electrode manufactured in the step (1), and a voltage can be applied between the pair of electrodes to accumulate charges.

  The counter electrode is not limited as long as it has conductivity, but examples thereof include a conductive plate and a conductive film disposed on an insulating plate. As an example of what includes a conductive plate, for example, a metal plate and a carbon plate can be exemplified, and as a conductive film disposed on an insulating plate, for example, glass, polyester film, On an insulating plate such as a polycarbonate film, ITO (indium tin oxide), IZO (indium zinc oxide), FTO (fluorine-doped tin oxide), ATO (aluminum-doped tin oxide), GTO (gallium-doped tin oxide), etc. The thing which has arrange | positioned the electroconductive film | membrane can be illustrated. In addition, from the viewpoint of productivity, mechanical strength, price, and lightness, it is preferable that ITO is formed on a metal plate or a glass substrate.

  In addition, although the thing of the example shown above can be used as it is for the counter electrode, the electrode produced in the step (1) can of course be adopted, and both of the pair of electrodes can be used in the step (1). From the viewpoint of increasing the amount of accumulated charge, it is more preferable to use the electrode fabricated in (1).

  In this step, the distance between the counter electrode and the electrode prepared in the above (1) is not limited, but is preferably 10 μm or more and 5 cm or less, and more preferably 100 μm or more and 1 cm or less. By setting the thickness to 10 μm or less, it is possible to cause sufficient growth of the electric double layer for causing the electrochemical reaction of charge / discharge, and by setting the thickness to 100 μm or more, this effect becomes remarkable. On the other hand, if it is 5 cm or less, it is possible to reduce the weight and size, and if it is 1 cm or less, this effect becomes remarkable.

  In this step, a capacitor electrolyte layer is filled between the pair of electrodes. By doing in this way, it becomes possible to flow the electric current by ionic conduction, and it becomes possible to increase the amount of electrical storage. In this step, the capacitor electrolyte may be filled with the surface tension after the pair of electrodes are arranged, or the pair of electrodes are made to face each other by inserting the pair of electrodes into the capacitor electrolyte. Alternatively, a porous insulating spacer containing an electrolyte may be arranged between them.

  In this step, the capacitor electrolyte layer is a layer containing an electrolyte, and may be an electrolytic solution having a solvent containing a supporting electrolyte, a gel electrolyte, or a solid electrolyte. Also good.

  In the present embodiment, when the capacitor electrolyte layer is an electrolytic solution, the solvent is not limited as long as the electrolyte can be retained, but water or an organic solvent can be employed, and the operating voltage can be reduced. From the viewpoint of expansion and improvement of energy density, an organic solvent may be used. In the case of an organic solvent, although not limited, acetonitrile, propylene carbonate, N-methylpyrrolidone, γ-butyrolactone, benzonitrile, methylene chloride, tetrahydrofuran / propylene carbonate, dimethylformamide, dimethyl sulfoxide, methanol, ethanol, and Examples of these solvents include those that dissolve in water but are mixed with water.

In the present embodiment, when the capacitor electrolyte layer is an electrolytic solution, the supporting electrolyte is not limited, but when the solvent is water, for example, LiCl, LiBr, Li ₂ SO ₄ , LiOH, LiClO ₄ , Mention may be made of NaCl, NaBr, Na ₂ SO ₄ , NaOH, NaClO ₄ , KCl, KBr, K ₂ SO ₄ , KOH, KClO ₄ , and (C ₂ H ₅ ) ₄ NOH, and their hydrates, From the viewpoint of forming a cobalt nanostructure having a large actual surface area, lithium sulfate monohydrate is more preferable. When the solvent is an organic solvent, for example, (C ₂ H ₅ ) ₄ NClO ₄ , (C ₂ H ₅ ) ₄ NF ₄ , (C ₂ H ₅ ) ₄ NPF ₆ , (C ₄ H ₉ ) ₄ NClO ₄ , (C ₄ H ₉ ) ₄ NF ₄ , (C ₄ H ₉ ) ₄ NPF ₆ , LiClO ₄ , NaClO ₄ , KClO ₄ , and (C ₄ H ₉ ) ₄ NOH. Moreover, when forming the capacitor which combined the cobalt nanowire or the cobalt oxide nanowire, and the water free solvent, from the viewpoint of the scientific stability of cobalt and cobalt oxide, LiOH, NaOH, KOH, (C ₂ H ₅ ) ₄ NOH and (C ₄ H ₉ ) NOH are preferred.

  The amount of the supporting electrolyte contained in the electrolyte in this step is not limited, but is preferably 0.01 parts by weight or more and 300 parts by weight or less when the weight of the solvent is 100 parts by weight. More preferably, it is 0.1 parts by weight or more and 40 parts by weight or less. When the amount is 0.01 parts by weight or more, sufficient electric conduction of the electrolytic solution can be ensured, and when the amount is 300 parts by weight or less, an excessive increase in the viscosity of the electrolytic solution can be suppressed, and charging and discharging are involved. It has the effect of not inhibiting ion transport.

  In addition, as a method of filling the electrolyte solution between the pair of electrodes, a method of injecting the electrolyte solution using surface tension between the pair of electrodes can be adopted, or a porous insulating property containing the electrolyte can be adopted. It is also possible to arrange the spacers in between.

  In this step, an example of using a gel electrolyte as the electrolyte is not limited, but for example, a gel polymer electrolyte is preferable. Examples of the gel polymer electrolyte include, but are not limited to, polyethylene oxide, polyacrylonitrile, poly (vinylidene fluoride), and polymethyl methacrylate.

  In this step, examples of using a solid electrolyte as the electrolyte include, but are not limited to, zirconia, zinc oxide, magnesium oxide, organic polymers, and conductive polymers.

  In this step, a counter electrode is prepared and arranged to face the electrode on which the cobalt nanostructure is formed and the capacitor electrolyte layer is filled between them. The procedure for filling the layers may be simultaneous. FIG. 2 shows an outline of the structure of a capacitor manufactured by this method.

  As shown in the figure, the capacitor 1 includes a pair of opposing electrodes 2a and 2b and cobalt nanostructures 3a and 3b formed on at least one of the pair of electrodes (both the pair of electrodes in the example of the figure). And a capacitor electrolyte layer 4 disposed between the pair of electrodes.

  In addition, the capacitor is connected to an external driving device, and accumulates charges by applying a pair of voltages, and can discharge the accumulated charges by short-circuiting. The voltage to be applied is not limited as long as it can be charged and does not exceed the decomposition voltage of the material, but it is preferably 0.05 V / cm or more and 10,000 V / cm or less in terms of the electric field between the electrodes. More preferably, it is more preferably 10 V / cm or more and 1000 V / cm or less.

  In this capacitor, the cobalt nanostructure is arranged on the electrode, so that the actual surface area of the electrode is expanded, and the surface of the cobalt nanostructure undergoes reversible electrochemical oxidation (charge) and reduction (discharge). Therefore, the electrochemical capacitor has higher energy and higher output and exhibits more stable charge / discharge characteristics. This capacitor is classified as a redox capacitor because it uses a reversible electrochemical reaction that occurs on the surface of the cobalt nanostructure.

  In particular, the cobalt nanostructure according to this embodiment is obtained by immersing an electrode in an electrolytic solution, electrolyzing the electrolytic solution in a magnetic field, and depositing the cobalt nanostructure on one of the pair of electrodes. Cobalt nanostructures are fine and complex nanostructures. The cobalt nanostructure forms a nano space formed by the MHD effect and the micro MHD effect, realizes a wider real surface area, exhibits a high-speed ion transport effect, and exhibits higher capacitor characteristics.

  In this embodiment, the cobalt nanostructure is formed by electrolyzing an electrolytic solution in a magnetic field, and has a complicated and fine structure that enables high-speed ion transport rather than a completely random state. It has something. As a result, the actual surface area of the electrode can be increased, and the above functions can be further improved. Although the degree of this fine structure is not particularly limited, it can be described that a nano-level structure is formed in a micro-level fine structure.

  As described above, according to the present embodiment, it is possible to provide a capacitor capable of achieving higher energy and higher output, a method for manufacturing the capacitor, and a method for manufacturing a cobalt nanostructure that can be used for the capacitor.

  Here, an experiment was actually performed on the method for producing a cobalt nanostructure according to the above embodiment, and the effect was confirmed. This will be specifically described below.

First, an electrolyte containing 19 mM hexaamminecobalt [Co (NH ₃ ) ₆ ] Cl ₃ and 0.1 M lithium sulfate Li ₂ SO ₄ as a supporting electrolyte was prepared in distilled and ion-exchanged water. This electrolyte was put in a chamber, an ITO glass substrate was inserted as a working electrode, and a platinum plate was inserted as a counter electrode, and at −18 ° C., −1.03 V vs. A potential of SCE (saturated calomel electrode) was applied. At this time, a magnet is arranged so as to sandwich the pair of opposing electrodes in a direction substantially perpendicular to or parallel to the surfaces of the pair of opposing electrodes, and the static magnetic field is 0 mT (magnetic field) in this direction. No application), 30 mT, 60 mT, and 90 mT. FIG. 3 shows an outline of the apparatus used in the electrolysis. Further, the energization amount of electricity was set 0.5~3.0C / cm ^2, were prepared six samples respectively 0.5 C / cm ² intervals. In this example, the magnets were neodymium magnets, which were opposed to each other and controlled while checking the magnetic field strength with a Tesla meter (Kanetec Tesla meter TM-701).

  As a result, a pair of electrodes for a total of 36 types of capacitors including two types of magnetic field directions, three types of magnetic field strengths, and six types of electric quantities were produced.

First, cyclic voltammetry was performed on these electrodes. The results are shown in FIG. 4 and FIG. FIG. 4 shows the result of the electrode when electrolytic reduction is performed with a static magnetic field of 30 mT, and FIG. 5 shows the result of the electrode when electrolytic reduction is performed with a static magnetic field of 60 mT. The above figures are examples in which the amount of electricity supplied is 1.0 C / cm ² . The cyclic voltammetry is a result of immersing these electrodes in a 0.1 M LiOH aqueous solution under the condition of 5 mV / s.

  As a result, in both parallel (horizontal) and vertical cases, it was confirmed that the peak value of the current density was improved compared to the case where no magnetic field was applied, and that the function could be improved. confirmed.

Moreover, the charge / discharge test was done with respect to the produced electrode. First, the result is shown in FIG. This figure shows an example in the case of applying an applied electricity amount of 1.0 C / cm ² and applying a magnetic field of 3.0 mT perpendicularly or in parallel to the substrate, or no application. As a result, the charge / discharge characteristics when a magnetic field was applied confirmed that the charge / discharge time was longer than when no magnetic field was applied, and the specific capacity of charge / discharge was increased.

This time, with respect to the same charge / discharge test as described above, the characteristics were evaluated by varying the amount of electricity supplied. The results are shown in FIGS. 7, using a substrate prepared by a magnetic field 3.0mT applied in a direction perpendicular to the substrate, if each having different current electrical quantity 0.5~3.0C / cm ² by 0.5 C / cm ² FIG. 8 shows the results related to the charge / discharge test in FIG. 8, FIG. 8 shows the results related to the charge / discharge test in the case of using the substrate created by applying a magnetic field of 3.0 mT in the direction parallel to the substrate, and FIG. 9 does not apply the magnetic field to the substrate. The result regarding the charging / discharging test in the case of using the board | substrate created by is shown, respectively. As a result, it is confirmed that the time to reach the same potential value increases as the energization amount approaches 2.0 C / cm ² when applied perpendicularly or parallel to the substrate, but decreases as it increases. did it. On the other hand, when no magnetic field was applied, it was confirmed that the time required to reach the same potential increased as the amount of electricity supplied increased.

Next, the dependency of the specific capacity Cm on the amount of electricity supplied was confirmed. The result is shown in FIG. The magnetic field strength was constant at 30 mT. As a result, it was confirmed that the specific capacity Cm increased at any energized electricity. In particular, at the same magnetic field strength, when the magnetic field is up to 2.0 C / cm ² , the ratio when the magnetic field is applied in a direction substantially perpendicular to the substrate is higher than that when the magnetic field is applied in a direction substantially parallel to the substrate. When the capacity is increased and is 2.0 C / cm ² or more, the value of Cm approaches that when no magnetic field is applied, and the effect of applying the magnetic field decreases.

Further, the dependency of the specific capacity Cm on the amount of electricity supplied was confirmed by changing the strength of the magnetic field. The results are shown in FIGS. Note that FIG. 11 uses a substrate created by applying a magnetic field of 0 mT (no magnetic field applied), 30 mT, 60 mT, or 90 mT in a direction perpendicular to the substrate, and the amount of electricity supplied is 0 to 0.5 to 3.0 C / cm ² . The results are shown in the case of different values by 5 C / cm ² .

According to this result, it was confirmed that the specific capacity was greatly improved in any case with the same energization amount as compared with the case where no magnetic field was applied. In particular, the amount of energized electricity has a peak in the vicinity of 2.0 C / cm ^2, and it has been confirmed that the effect of improving the specific capacity is particularly high in this vicinity.

Here, the dependency of the roughness factor r of the fabricated electrode on the amount of electricity applied was confirmed. The results are shown in FIGS. FIG. 13 shows an example when a magnetic field perpendicular to the substrate is applied, and FIG. 14 shows an example when a magnetic field parallel to the substrate is applied. As shown in these figures, as a whole, when the magnetic field is applied, the roughness factor r increases with the same amount of electricity supplied, and the roughness factor r increases even when the amount of electricity supplied is increased. I can confirm. However, in the case where a magnetic field is applied, when the amount of energized electricity exceeds 3.0 C / cm ² , the roughness factor decreases compared to the case where the magnetic field is not applied even if the amount of energized electricity is the same. (30 mT and 60 mT in FIG. 13 and 30 mT in FIG. 14). Here, the roughness factor is defined as the ratio of the actual surface area to the area (apparent area) of the smooth surface.

Incidentally, in FIG. 15, energization amount of electricity 1.0 C / cm ^2, the electrode was produced under the conditions of applying a magnetic field of 30mT in a direction perpendicular to the substrate, the energization amount of electricity 1.0 C / cm ^2, with respect to the substrate SEM images of an electrode produced under a condition in which a magnetic field of 30 mT was applied in a parallel direction, an amount of electricity of 1.0 C / cm ² , and an electrode produced under a condition in which no magnetic field was applied to the substrate are shown. According to these figures, it can be seen that when created without applying a magnetic field, thin and long nanowires are formed and fused together at the tip (white contrast portion). And the fraction area | region with a diameter of 3-6 micrometers was formed. On the other hand, when a magnetic field was applied, thick and short nanowires were formed, and a smaller fractional space with a size of submicron to 2 μm was formed. In such a smaller fractional space, the distance over which ions diffuse is reduced and high-speed ion transport is possible. With the increase in the area of the interface in contact with the electrolytic solution, it can be considered that due to this high-speed ion transport effect, the charge / discharge capacity Cm increased when a magnetic field was applied compared to when no magnetic field was applied. In FIG. 19 to be described later, each scale bar is 20 μm.

FIG. 16 shows a comparison of SEM images when a magnetic field is applied in a direction perpendicular to the substrate in a state where the amount of electricity supplied is 1.0 C / cm ² . As a result, it was confirmed that the network-like cobalt nanostructures were more clearly confirmed by applying a high magnetic field, and that the surface was roughened by applying the magnetic field. On the other hand, FIG. 17 shows a comparison of SEM images when a magnetic field is applied in a direction parallel to the substrate in a state where the amount of electricity supplied is 1.0 C / cm ² . Also in this result, it was confirmed that the network-like cobalt nanostructure was more clearly confirmed by applying a high magnetic field, and the surface was roughened by applying the magnetic field.

FIG. 18 shows a comparison of SEM images when the amount of energized electricity is changed under the condition that a magnetic field of 90 mT is applied in a direction perpendicular to the substrate. As a result, in the case of 0.5 C / cm ^2, a fine mesh-like cobalt nanostructure can be confirmed, while the mesh line becomes thicker and the amount of cobalt nanostructure becomes larger as the amount of energized electricity is increased. It can be confirmed that the nanowire structure is further formed in the fractionation space, resulting in a more complicated structure. This complication of the structure suggests that the effect of fast ion transport is more exhibited as the area of the interface in contact with the liquid solution increases. In the case of 3.0 C / cm ² , the network structure collapsed and the size of the fractionation space increased. This increase in size is construed as fostering fast ion transport and consequently leading to a decrease in Cm.

FIG. 19 shows a comparison of SEM images when the amount of energized electricity is changed under the condition that a magnetic field of 90 mT is applied in a direction parallel to the substrate. As a result, in the case of 0.5 C / cm ^2, a fine mesh-like cobalt nanostructure can be confirmed, while the mesh line becomes thicker and the amount of cobalt nanostructure becomes larger as the amount of energized electricity is increased. A tendency to increase can be confirmed. In the case of 3.0 C / cm ² , it was confirmed that the network structure was changed and the linear cobalt nanostructures were arranged so as to overlap each other. That is, when it becomes 3.0 C / cm ² or more, as in the case of applying a vertical magnetic field, the size of the fractionation space increases, and the increase in size fosters fast ion transport, resulting in a decrease in Cm. Interpreted.

  As described above, the effect of the present invention could be confirmed by this example.

  The present invention has industrial applicability as a capacitor and a manufacturing method thereof.

Claims (7)

  A method for producing a cobalt nanostructure, wherein a pair of electrodes is immersed in an electrolytic solution containing a cobalt complex, and the electrolytic solution is electrolyzed in a magnetic field to deposit a cobalt nanostructure on one of the pair of electrodes.   The method for producing a cobalt nanostructure according to claim 1, wherein the magnetic field is a static magnetic field and is in a range of 1 mT to 10 T.   The method for producing a cobalt nanostructure according to claim 2, wherein the static magnetic field is substantially parallel or substantially perpendicular to the opposing surfaces of the pair of electrodes. The production of the cobalt nanostructure according to claim ² , wherein an amount of current flowing between the pair of electrodes in electrolysis of the electrolytic solution according to claim 2 is in a range of 0.01 C / cm ² or more and 10.0 C / cm ² or less. Method.   A capacitor in which the electrode on which the cobalt nanostructure according to claim 3 is deposited is disposed to face the counter electrode through the capacitor electrolyte layer.   A capacitor in which the electrode on which the cobalt nanostructure according to claim 4 is deposited is disposed to face the counter electrode via the capacitor electrolyte layer. The capacitor according to claim 4, wherein an amount of the cobalt nanostructure deposited on the electrode is in a range of ² μg / cm ^{2 to} 2000 μg / cm ² .