JP6494337B2 - Capacitor and manufacturing method thereof - Google Patents

Description

  The present invention relates to a capacitor and a manufacturing method thereof.

  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. An electrochemical capacitor is a device for accumulating and outputting electric charges by using an electrochemical action. Typical examples thereof include an electric double layer capacitor, and a redox that has recently been newly proposed. There is a capacitor.

  Here, the electric double layer capacitor has a pair of electrodes and an electrolytic solution disposed between the pair of electrodes, and is formed by adsorption of ions (non-Faraday reaction) generated at the interface between the electrolytic solution and the electrodes. It is a capacitor that can store electric charges using an electric double layer, and can be increased in capacity by using a carbon material or the like having a very large specific surface area as an electrode.

  On the other hand, a redox capacitor is a capacitor capable of accumulating charges using a pseudocapacitance expressed by a plurality of continuous redox (redox) reactions of an active material, and is larger than the electric double layer capacitor described above. There is an advantage that it is superior in capacity and instantaneous charge / discharge characteristics than a battery, and is expected to be larger.

  As a known technology of the capacitor related to the above, for example, there is a technology described in Patent Document 1 below.

JP 2014-130980 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 to increase 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 cobalt nanostructures, the structure is refined by the MHD effect and the micro MHD effect, the actual surface area is large, and the fast ions 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 are immersed in an electrolytic solution containing a cobalt complex, and the temperature is higher than 40 ° C. and lower than 80 ° C. in a magnetic field. The electrolytic solution is electrolyzed to deposit cobalt nanostructures on one of the pair of electrodes.

  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 position of a board | substrate and an applied magnetic field. It is a section schematic diagram of a capacitor concerning an embodiment. It is a figure which shows the outline of the apparatus used in the electrolysis. It is a figure which shows the SEM image of the produced cobalt nanostructure. It is a figure which shows the result of having performed cyclic voltammetry with respect to the electrode produced in the Example. It is a figure which shows the result of having done the constant current charging / discharging test produced in the Example. It is a figure which shows the apparatus structure used in the Example, and the schematic diagram of a magnetic field direction. It is a figure which shows the result of the cyclic voltammetry performed in the Example. It is a figure which shows the SEM image of the cobalt nanostructure in the electrode produced in the Example. It is a figure which shows the result of having performed the constant current charging / discharging test using the galvanostat with respect to each electrode in an Example. It is a figure which shows the result of having confirmed an electrostatic capacitance, discharge capacity, energy density, and a charge / discharge curve with respect to each electrode in an Example. It is a figure which shows the result of having measured about the repetition characteristic of the cobalt nanostructure in the case of 120 mT. It is a figure which shows the SEM image of the cobalt nanostructure which concerns on an Example. It is a figure which shows the result of having performed constant current charging / discharging using the galvanostat in an Example. It is a figure which shows the result of the charging / discharging repetition characteristic of 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.

  A method for manufacturing a capacitor according to the present embodiment (hereinafter referred to as “the present capacitor”) (hereinafter referred to as “the present method”) includes (1) a pair of electrodes immersed in an electrolytic solution containing a cobalt complex, A step (S1) of electrolyzing the electrolytic solution within a temperature range higher than 80 ° C. and lower than 80 ° C. to deposit cobalt nanostructures on one of the pair of electrodes; and (2) an electrode on which the cobalt nanostructures are deposited, A step (S2) of disposing the counter electrode opposite to the capacitor electrode layer.

  In this method, (1) a pair of electrodes is immersed in an electrolytic solution containing a cobalt complex, and electrolysis is performed in a magnetic field within a temperature range higher than 40 ° C. and lower than 80 ° C., and a cobalt nanostructure is formed on one of the pair of electrodes. The step of depositing is a method of manufacturing a cobalt nanostructure, and 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 nanostructures.

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 NBF ₄ , (C ₂ H ₅ ) ₄ NPF ₆ , (C ₄ H ₉ ) ₄ NClO ₄ , (C ₄ H ₉ ) ₄ NBF 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, It 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 electrolytic 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. Reduction is preferred. 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. In addition, as the potential at this time, for example, when SCE is used for the reference electrode, −0.5V to −2V is applied
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.

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 applying a static magnetic field, for example, a permanent magnet is used, and this pair of electrodes can be easily arranged between the N pole and S pole of the permanent magnet. If the magnetic field formed by the magnet is sufficiently strong, One permanent magnet may be arranged near the electrode. 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. FIG. 1 schematically shows an example of the relationship between an applied magnetic field and electrodes.

  The direction of the applied magnetic field is preferably substantially parallel or substantially perpendicular to the electrode surface. Here, “substantially parallel” includes not only completely parallel, but also includes an error of several degrees between the electrode surface and the direction of the static magnetic field, including the case where it is not completely parallel. For example, an error of ± 5 degrees is included. Here, “substantially perpendicular” includes not only completely perpendicular, but also includes the case where the direction of the electrode surface is not completely parallel, between the electrode surface and the direction of the static magnetic field. An error range of about several degrees is included. For example, an error of ± 5 degrees is included.

  In this step, the magnetic field strength is preferably in the range of 1 mT to 10 T, and 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, the temperature during electrolysis is higher than 40 ° C. and lower than 80 ° C., preferably 50 ° C. or higher and 70 ° C. or lower. By setting it as said range, the characteristic which exceeds the characteristic of the capacitor reported until now can be acquired. Specifically, it is possible to express about twice as much capacity as that produced at room temperature. This effect will be apparent from the results of Examples described later.

  As described above, 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 the chemical stability of the cobalt nanostructure, a hydroxide is desirable. 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. Further, when forming a capacitor in which a cobalt nanostructure and an aqueous solvent are combined, LiOH, NaOH, KOH, (C ₂ H ₅ ) ₄ NOH and (C ₄ ) are used from the viewpoint of chemical stability of the cobalt nanostructure. H ₉ ) NOH is 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, arranged opposite to 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.

(Confirmation of temperature dependence)
First, an electrolytic solution containing 19 mM of hexaamminecobalt [Co (NH ₃ ) ₆ ] Cl _{3 represented} by the following formula and 0.1 M of lithium sulfate Li ₂ SO ₄ in water subjected to distillation and ion exchange was prepared. This electrolyte is placed in the main chamber of the glass, and an ITO glass substrate is inserted as a working electrode and a counter electrode is inserted as a platinum plate, and the working electrode is -1.03 V at a temperature of 40 ° C., 50 ° C., 60 ° C., 70 ° C. or 80 ° C. vs. A potential of SCE (saturated calomel electrode) was applied. FIG. 3 shows an outline of the apparatus used in the electrolysis. In this case, the amount of electricity supplied was 1.5 C / cm ² . As a result, formation of cobalt nanostructures was confirmed on the electrode substrate. In addition, the SEM image of the cobalt nanostructure produced in FIG. 4 is shown. The length of the scale bar in the figure is 50 μm.

  According to this result, cobalt nanowires were formed, and almost no change in form was observed up to 60 ° C., while the tendency of the cobalt nanostructure wires to be shortened after 70 ° C. was confirmed. It was confirmed that nanowires having an aspect ratio lower than that at room temperature were formed when the temperature exceeded ℃. The reason for this is thought to be due to the reasoning that ammonia obtained with the shape control agent did not adsorb well on the side surfaces of the nanowires, making it difficult to grow in a one-dimensional direction.

  Next, cyclic voltammetry was performed on the electrodes prepared at the temperatures of 40 ° C., 60 ° C., and 80 ° C. The result is shown in FIG. The present cyclic voltammetry is a result obtained by immersing these electrodes in a 0.1 M LiOH aqueous solution under the conditions of a sweep range of 0.05 to 0.55 V and a sweep speed of 10 mV / s.

  As a result, it was confirmed that the current density was highest at 60 ° C. and decreased at 80 ° C. From this result, it was confirmed that improvement of capacitor characteristics can be expected depending on the solution temperature at the time of electrode formation.

Moreover, the constant current charging / discharging test was done with respect to the produced electrode. The charge / discharge characteristics obtained as a result are shown in FIG. 6, and the transition of the capacity obtained from this figure is shown in Table 1 below. In the constant current charge / discharge test, a galvanostat (HOKUTO DENKI Co. HJ1010mSM8A), a three-electrode glass cell was used. The counter electrode was a platinum plate, and the electrolyte was lithium hydroxide (0.1M).

  As a result, it was confirmed that the highest capacitor characteristics were exhibited at 60 ° C. This is considered that although the wire form did not change, the charge / discharge capacity was increased by raising the temperature to 60 ° C., so that the cobalt hydroxide layer was increased. Cobalt nanowires have charge / discharge characteristics in the cobalt hydroxide part on the surface, so increasing the temperature during electrode formation increases the cobalt hydroxide layer, and this increase in the cobalt hydroxide layer leads to improved capacitor characteristics. It can be thought that.

(Confirmation of magnetic field dependence)
Next, as in the case of confirming the temperature dependency, the solution temperature at the time of electrode formation is set to 20 ° C., while a neodymium magnet is disposed, and the magnetic field strength applied to the electrode is set to 30 mT, 60 mT, 90 mT or An electrode was formed at 120 mT. Moreover, the arrangement direction of the magnet was also adjusted, and a plurality of magnetic field application directions were also adjusted. A schematic diagram of the device configuration and the magnetic field direction in this case is shown in FIG.

  As a result, in all cases, formation of a gray-black thin film of cobalt nanostructures on the working electrode was confirmed along with reduction of the cobalt complex.

  Here, cyclic voltammetry was performed on each of the resulting electrodes. The result is shown in FIG. In this figure, the results for 0 mT (no magnetic field applied) and 120 mT electrodes are shown. As a result, it was confirmed that the capacitor characteristics were improved by applying the magnetic field.

  Moreover, the SEM image of the cobalt nanostructure in each said produced electrode is shown in FIG. The scale bar in the figure is 40 μm in (a) and (b), and 10 μm in (c) and (d).

  Moreover, the constant current charging / discharging test was done with respect to each produced said electrode using a galvanostat. The result is shown in FIG. In this figure, A is when there is no magnetic field, B is when 60 mT magnetic field is applied in the vertical direction from the surface of the electrode to the cobalt nanostructure, and C is when 60 mT magnetic field is applied from the direction substantially parallel to the electrode surface. D represents the case where a cobalt nanostructure was applied vertically from the back side of the electrode with a magnetic field of 60 mT.

  As a result, it can be seen that there is almost no difference in specific capacity depending on the magnetic field direction, and it does not depend greatly on the magnetic field direction.

  Furthermore, the capacitance, discharge capacity, energy density, and charge / discharge curve were confirmed again for each of the electrodes produced. The result is shown in FIG. The magnetic field in this case was set to the same magnetic field direction as “C” in FIG.

  As a result, it can be confirmed that each characteristic is improved as the applied magnetic field intensity is increased, but since the increase amount is small, it is predicted that the characteristic is saturated at about 200 mT. . In addition, when it exceeds about 140 mT, since the cobalt nanostructure will peel from the ITO surface, it is preferable to keep the magnetic field below this.

Moreover, it measured about the repetition characteristic of the cobalt nanostructure in the case of 120 mT. The result is shown in FIG. The number of repetitions of the reduction to the capacity of 50% is 10 ³ to 10 ^{5 for the} redox capacitor, but this capacitor satisfies this condition even at 10 ³ and is considered to have a predetermined durability. It is done.

(Confirmation of effects of magnetic field application and temperature adjustment)
In addition, while the same as in the above example, the electrode was fabricated with a magnetic field of 120 mT and a solution temperature at the time of electrode formation of 20 ° C. FIG. 13 shows an SEM image of the cobalt nanostructure produced in this case.

  Next, constant current charge / discharge was performed using a galvanostat under the same conditions as described above. The result is shown in FIG.

  As a result, a capacitance of 1510 F / g could be confirmed, and a value more than 10 times that of a practical electrochemical capacitor could be confirmed. On the other hand, the discharge capacity was comparable to that of a commercially available lithium ion battery (100 to 200 mAh / g).

  Furthermore, repeated characteristics were also confirmed under the same conditions as described above. The result is shown in FIG.

As a result, since the can also maintain the original 50% or more as was repeated 10 ³ times of charge and discharge, it was confirmed that the durability is sufficiently maintained.

  As mentioned above, the effect of this invention has been confirmed by the present Example.

  The present invention has industrial applicability as a capacitor.

Claims (2)

Cobalt in which a pair of electrodes is immersed in an electrolytic solution containing a cobalt complex, and the electrolytic solution is electrolyzed in a magnetic field within a temperature range of 50 ° C. or higher and 70 ° C. or lower to deposit cobalt nanostructures on one of the pair of electrodes. Manufacturing method of nanostructure. 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.