JP2014075466A - Electric double layer capacitor for high power - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a capacitor suitable for high power by increasing the degree of freedom of collector electrode arrangement.SOLUTION: A recirculation pump 36 for recirculating electrolyte in two kinds of inter-electrode spaces for positive electrode and negative electrode immersed in electrolyte 14, e.g., the inner and outer spaces of an electrode unit, is provided. Since migration of ions does not depend on the electrical mobility, individual electrodes for positive electrode and negative electrode are not required to be paired. A plurality of electrodes may be collected as electrode units 16, 18, and then configured and arranged freely even at separated positions.

Description

  The present invention relates to an electric double layer capacitor, and more particularly to a high power electric double layer capacitor.

  Electric double layer capacitors have traditionally been used only in low-power electronic devices, but recently they have also been used in high-power applications, such as being used as starting power sources for hybrid vehicles.

  However, although there is an advantage that a large current can flow in a short time, the low energy density is a drawback, and the prospect of further use for high power has not spread. Currently, ideas are emerging in the direction of hybridization with chemical batteries in order to increase energy density, but another reason why conventional electric double layer capacitors have only been given a supplementary role is to connect loads. In this case, the output voltage current was decreased linearly with time. If the electric double layer capacitor has a large capacity as in the present invention, voltage adjustment is performed by dividing it into subunits in an external circuit, so that voltage and current are constant until a certain time even when a load is connected like a chemical battery. And has an independent battery function value. If it does so, it can also stand out over a chemical battery from the original property of the electric double layer capacitor that a large current can be supplied in a short time.

  Electric double layer capacitors have a simple operating principle and are expected to be cost-effective if efficiency is increased. Suitable for high power type. Recently, the use of natural energy has been screamed, and a stationary type high-power renewable energy utilization facility has been planned. For this purpose, a large-power storage facility is absolutely necessary.

  Usually, an electric double layer capacitor is immersed in an electrolytic solution by inserting a separator between positive and negative electrode plates. Even a capacitor of about 100 farads currently on the market has a small distance between the electrodes and is 1 mm or less. Normally, in an electrochemical cell, the electric field applied between the collector electrodes is also a means for transporting ions in the liquid, but at the same time, the electric field also serves to cause charge transfer from the electrode plate to the electrolyte, A form of parallel electrode plates of alternating positive and negative arrangement in which different electrode plates are arranged to face each other is absolutely necessary. Conventional electric double layer capacitors are also within the scope of this idea, and adopt the form of parallel electrode plates with positive and negative alternating arrangements (see Patent Documents 1 and 2).

JP-A-11-121305 JP 2009-81434 A

  The present invention can adopt not only parallel collector plates with positive and negative alternating arrangements as electrode arrangements but also other arrangement forms, and an electric double layer having a high degree of freedom with respect to electrode arrangement and easy to use for high power. The object is to provide a capacitor.

  The electric double layer capacitor of the present invention comprises an electrolytic bath containing an electrolytic solution, a positive electrode immersed in the electrolytic solution and including a plurality of electrodes, and electrically connected to each other, and a plurality of electrodes immersed in the electrolytic solution. A negative electrode that is electrically connected to each other, and a reflux mechanism that recirculates the electrolyte so that the electrolyte moves in the space between the electrodes in both the positive electrode and the negative electrode.

As the electrolytic solution, either an aqueous electrolytic solution or a non-aqueous electrolytic solution can be used. As the aqueous electrolyte, for example, an aqueous solution of monovalent ions or multivalent ions such as KCl, NaCl, CaCl ₂ can be used. As the nonaqueous electrolytic solution, for example, an organic electrolytic solution using propylene carbonate as an organic solvent and a quaternary ammonium salt such as tetraethylammonium tetrafluoroborate as a supporting electrolyte can be used. Organic electrolytes have the advantage that the usable voltage and thus the stored energy can be increased. However, the type of the electrolytic solution is not limited to those illustrated. For example, any electrolytic solution that is used in a conventional electric double layer capacitor, such as an ionic liquid that is a liquid in which anions and cations exist in an ion-bonded state, can be used.

  The shape of the electrode is not particularly limited, and may be a rod shape or a mesh shape in addition to a plate shape. The plate electrode uses a metal flat plate or a substrate having a plurality of holes in it as a collecting electrode. The rod-shaped electrode uses a base made of a metal rod as a collecting electrode. The mesh electrode uses a base made of a metal mesh in a flat plate shape as a collecting electrode. Since an electrode has a larger ion adsorption surface area, it is preferable that a carbon-based ion adsorption layer having an effective surface area larger than the surface is formed on the surface of a metal substrate or substrate as a collecting electrode. As the carbon ion adsorption layer, activated carbon materials such as activated carbon particles and activated carbon fibers, or carbon fibers and carbon nanotubes are preferable. Since carbon fibers and carbon nanotubes can increase the surface area of the ion-adsorbing layer, they are more convenient for realizing a small-sized, high-power electric double layer capacitor by reducing the electrode volume.

In an electric double layer capacitor, there is no charge transfer between the electrode and the electrolyte, and the positive and negative charges just face each other by the Coulomb force at the interface. In the present invention, the mechanism is a reflux mechanism. In this case, it is only necessary to gently reflux the electrolytic solution. For example, like an electrode plate in which an activated carbon film is formed on the surface of a plate-like collector electrode, the effective area for adsorbing ions is wide, and the electrophoretic velocity of ions in the electrolyte is slow (especially for organic solutions). Reflux is particularly effective when the ion electrophoresis rate is slow. Here, “slowly” means that the moving speed of the electrolyte is about 1 mm / second or less. Even at such a low speed, it is sufficiently faster than the ion transfer speed under an electric field of 1 V / cm. For example, even in the case of ions in an aqueous solution that is much faster than ions in an organic solution, the ion movement speed under an electric field of 1 V / cm is only about 1 × 10 ⁻³ cm / second.

  As described above, in the present invention in which ions in the electrolyte solution are moved by refluxing the electrolyte solution as described above, the conventional arrangement of the electrode and the shape thereof are not considered because it does not depend on the electric mobility of ions due to an electric field as in the conventional electric double layer capacitor. This gives rise to a degree of freedom that was not possible. This is the greatest advantage of the present invention. As a necessary condition, it is only necessary to have positive and negative electrodes in the electrolytic solution, and it should show a certain potential in a certain place in the electrolytic solution, and the ion is determined by the difference between the potential Va at that place and the potential V0 of the electrode. Although it migrates to the electrode, an ion double layer is formed on the ions in the immediate vicinity of the electrode by the Coulomber between the surplus electrons of the electrode. This mechanism is the same as that in which ions are attracted around the surface-charged colloidal particles. Therefore, the electrolyte solution may be refluxed while the electrolyte solution is filled with two positive and negative electrodes as much as possible, and ions may be delivered to the electrode interface. In this case, the arrangement and shape of the electrode plates are free. In such an electrode arrangement, each electrode can be fixed with, for example, activated carbon on both sides of the collector electrode. This is different from the conventional electric double layer capacitor in which only one side of the collector electrode can be used. This means that the capacity, and hence the charge storage capacity, is doubled.

  In a preferred mode, for example, as shown in an embodiment of FIG. 1 described later, the positive electrode and the negative electrode are each configured as an electrode unit in which a plurality of electrodes are assembled, and the electrode is in each electrode unit. Are electrically connected to each other. And the electrode unit for positive electrodes and the electrode unit for negative electrodes are installed in the position mutually separated.

  In this mode, for example, as shown in an embodiment of FIG. 3 to be described later, a plurality of positive electrode units and negative electrode units may be disposed in the electrolytic solution tank. In this case, the positive electrode units are electrically connected to each other, and the negative electrode units are also electrically connected to each other.

  In another form, for example, as shown in the embodiment of FIG. 4 described later, the positive electrode and the negative electrode are arranged so that the respective positive electrode and negative electrode are adjacent to each other. The electrodes are arranged alternately.

  The electrode is preferably arranged in the vertical direction, and an example of a preferable reflux mechanism in that case is an electrolyte supply port arranged below the electrode in the lower part of the electrolyte tank and an electrolysis provided in the upper part of the electrolyte tank. A liquid discharge port and a circulation pump for sending the electrolyte discharged from the electrolyte discharge port to the electrolyte supply port are provided. Then, the electrolytic solution flows from the bottom to the top between the electrodes.

  In the electric double layer capacitor of the present invention, since the electrolytic solution is refluxed in the space between the electrodes of the electrolytic solution tank, the degree of freedom regarding the electrode arrangement is increased. As a result, it becomes easy to increase the number of electrodes, which is suitable for high power use.

It is a figure which shows one Example, (A) is a schematic sectional drawing, (B) is sectional drawing in the AA line position of (A), (C) is the electrode plate used in the Example. The top view which shows one sheet, (D) is sectional drawing which shows one sheet of the same electrode plate. It is a top view of the embodiment. (A), (B) is a connection diagram which shows the example of the electrical connection of the Example provided with the some electrode unit for each for positive electrodes and negative electrodes. It is a schematic sectional drawing which shows other Example.

  One embodiment will be described with reference to FIGS. An electrolytic solution 14 is accommodated in a box-shaped electrolytic solution tank 12 made of an insulating material and opened at the top. The opening of the electrolytic solution tank 12 is closed by a lid 13 made of an insulating material.

  Electrolyte discharge ports 15 a to 15 d are provided at the same height on the four side surfaces at the upper part of the electrolyte solution tank 12, and these discharge ports 15 a to 15 d are disposed outside the electrolyte solution tank 12. 17. As will be described later, the electrolytic solution 14 is supplied to the electrolytic solution tank 12 from below, but in the electrolytic solution tank 12, the electrolytic solution 14 that has reached the discharge ports 15a to 15d passes through the discharge ports 15a to 15d. Since it is discharged | emitted by the tank 17, the liquid level of the electrolyte solution 14 in the electrolyte tank 12 is maintained in the position of the height of the discharge ports 15a-15d. On / off valves 19a to 19d are provided outside the electrolyte tank 12 at the discharge ports 15a to 15d. The on-off valves 19a to 19d select the four discharge ports 15a to 15d so that the flow of the electrolyte solution 14 in the electrolyte tank 12 can be adjusted, but the electrolysis is always performed from the four discharge ports 15a to 15d. When discharging the liquid 14, it is not necessary to provide the opening / closing valves 19a to 19d.

  The height of the mounting positions of the discharge ports 15a to 15d is set so that the electrolytic solution 14 has a liquid level that leaves some space at the top.

The electrolytic solution 14 is, for example, a KCl aqueous solution containing high concentration ions. The concentration is not particularly limited, but a higher concentration is more convenient because the ion concentration becomes higher. In addition, an aqueous solution such as NaCl or CaCl ₂ can be used instead of the KCl aqueous solution, and an organic electrolytic solution or an ionic liquid can also be used.

  A positive electrode unit 16 and a negative electrode unit 18 are immersed in the electrolytic solution 14. The liquid level of the electrolytic solution 14 is at the height of the discharge ports 15 a to 15 d, and there is some space in the upper part in the electrolytic solution tank 12. The electrode units 16 and 18 are immersed in a state in which a part of each upper part is exposed from the electrolytic solution 14. In this embodiment, one unit for each of the positive electrode unit 16 and the negative electrode unit 18 is provided.

  Each of the electrode units 16 and 18 is configured by a plurality of electrode plates 20, and the electrode plates 20 are electrically and mechanically connected to each other in each of the electrode units 16 and 18. Is integrated. The electrode plate 20 is rectangular as shown in the plan view of FIG. (C). For example, one side is a square having a side of, for example, 1 m. The electrode plate 20 is preferably provided with a plurality of holes 22 through which the electrolytic solution passes. The shape, size, and arrangement interval of the holes 22 are not particularly limited. The shape of the hole 22 may be circular or rectangular, and the size is suitably about 2 cm, for example, but it may be larger or smaller. The holes 22 are arranged at suitable intervals, which may be, for example, 5 cm or wider, and the intervals may or may not be constant. Further, in this embodiment, the electrolyte is refluxed so as to flow in the direction from the bottom to the top, so in some cases, the flow of the electrolyte through the electrode is not essential. Therefore, the hole 22 of the electrode plate 20 may not be provided.

  As shown in FIG. 1D, the electrode plate 20 has an aluminum plate with a thickness of, for example, 1 mm as a substrate 20a, and an activated carbon film 20b on both surfaces of the substrate 20a with a thickness of, for example, 0.5 mm. It is fixed. The activated carbon film 20b is formed by, for example, applying and curing activated carbon on the substrate 20a together with a binder.

  Each of the electrode units 16 and 18 is configured such that a plurality of electrode plates 20 are arranged in a vertical direction and fixed in parallel with each other at a predetermined interval, for example, a 2-3 mm interval. When the number of electrode plates 20 included in each electrode unit 16, 18 is about 10, the thickness of each electrode unit 16, 18 is about 4 cm. Each of the electrode units 16 and 18 is obtained by fixing at least the upper end portion of the electrode plate 20 included in each unit to a metal plate such as an aluminum plate by welding. In the embodiment of FIG. 1, the lower end side of the electrode plate 20 is also fixed to a connecting metal plate, for example, an aluminum plate by welding. Although the metal plate which fixes the upper end side of each electrode unit 16 and 18 may insulate the surface, since it does not contact the electrolyte solution 14, it does not need to insulate. When the lower end sides of the electrode units 16 and 18 are also fixed with a connecting metal plate, the connecting metal plate is in contact with the electrolytic solution 14, and therefore the surface is preferably covered with an insulating film.

  Thus, by fixing the upper end side and lower end side of the electrode plate 20 included in the unit, the arrangement of the electrode plate 20 included in the unit is stabilized. The electrode units 16 and 18 are also electrically connected by at least the upper end side being fixed by a metal plate, and the electrode plates 20 included in the electrode units 16 and 18 have the same potential.

  In this embodiment, since the electrode plates 20 in the electrode units 16 and 18 are at the same potential, it is not necessary to provide a separator for insulation in the electrode units 16 and 18. A separator for insulation may be provided between the electrode units 16 and 18.

  When a connecting metal plate is provided on the lower end side of each of the electrode units 16 and 18, the connecting metal plate is provided with a through-hole or groove for allowing the electrolyte solution 14 to flow upward from below. .

  Pipes 32a and 32b constituting electrolyte supply ports are arranged in parallel to each other below the electrode units 16 and 18 in the lower part of the electrolyte bath 12. The pipes 32 a and 32 b are arranged in a direction extending along the arrangement direction of the electrode plates 20 of the electrode units 16 and 18, and have a length over the entire length of the electrode units 16 and 18. The pipes 32a and 32b have a large number of holes 34 formed on their upper surfaces, and these holes 34 serve as electrolyte supply ports. The pipes 32 a and 32 b are connected to a circulation pump 36 disposed outside the electrolytic solution tank 12 through a pipe 35 a and 37 b through a hole 35 formed in a side surface of each central portion. The circulation pump 36 supplies the electrolytic solution from the lower part of the electrolytic solution tank 17 to the pipes 32 a and 32 b in the electrolytic solution tank 12 through the pipes 37 a and 37 b. The number of pipes 32a and 32b is not limited to two, and may be one or three or more.

  As the circulation pump 36, any pump can be used as long as the electrolyte does not directly contact the metal portion of the pump. An example of such a pump is a diaphragm pump.

  In this embodiment, the circulation pump 36, pipes 32a and 32b having an electrolyte solution supply port, electrolyte solution discharge ports 15a to 15d, and the electrolyte solution tank 17 constitute a circulation mechanism.

  The electrode units 16 and 18 are arranged so that the end portions to which the electrode plates 20 are fixed are the upper end and the lower end, and the respective upper end portions are in contact with and fixed to the inside of the lid 13 of the electrolytic solution tank 12. Yes. The inner width of the electrolyte bath 12, that is, the vertical dimension in FIG. 1A and the lateral dimension in FIG. 1B is larger than the lateral dimension of the electrode plate 20. In a state where the electrode units 16 and 18 are accommodated, there is a gap on the inner side surface of the electrolytic solution tank 12 as shown in FIG.

  Electrode terminals 28 and 30 are provided on the upper surfaces of the electrode units 16 and 18, and the electrode terminals 28 and 30 extend outside through the upper surface of the lid 13 of the electrolytic solution tank 12. The electrode terminals 28 and 30 protruding from the lid 13 serve as external connection terminals connected to an external circuit during charging and discharging.

  Screws are formed on the outer surfaces of the electrode terminals 28 and 30, and the upper ends of the electrode units 16 and 18 are fixed to the electrolyte bath by fixing the screws of the electrode terminals 28 and 30 protruding from the electrolyte bath 12 with nuts. The electrode units 16 and 18 are fixed in the electrolytic solution tank 12 in contact with the inside of the 12 lids 13.

  In this embodiment, at the time of charging, the external connection terminals 28 and 30 are connected to a power supply line of a solar power generation device or another power generation device to supply current, and the pump 36 is operated. By the operation of the pump 36, the electrolytic solution 14 is sent from the electrolytic solution tank 17 to the pipes 32 a and 32 b by the pump 36, discharged upward from the holes of the pipes 32 a and 32 b, and flows upward between the electrode plates 20. The electrolyte solution 14 is refluxed so as to be discharged to the electrolyte solution tank 17 through the solution discharge ports 15a to 15d. Due to the reflux of the electrolytic solution 14, the electrolytic solution flows between the electrode plates 20 and carries ions in the electrolytic solution 14 to the surface of the electrode plate 20, and an electric current supplied from the outside flows to the surface interface of the electrode plate 20. The electric double layer is quickly formed and charging is performed.

  At the time of discharging, the external connection terminals 28 and 30 are connected to a load of a home or facility. The operation at the time of discharging is the same as that of a conventional electric double layer capacitor. The pump 36 may or may not be activated during discharge. When neither charging nor discharging is performed, the pump 36 does not need to be operated.

  In the embodiment of FIGS. 1 and 2, the positive electrode unit 16 and the negative electrode unit 18 are arranged one by one in the electrolytic solution tank 12, but the electrode unit is arranged in the electrolytic solution tank 12. However, the number of the positive electrode units 16 and the negative electrode units 18 may be plural.

  FIG. 3 shows an embodiment in which two units of the positive electrode unit 16 and the negative electrode unit 18 are arranged in the electrolytic solution tank 12.

  In the embodiment of FIG. 3A, the positive electrode unit and the negative electrode unit are alternately arranged so that the positive electrode unit 16a, the negative electrode unit 18a, the positive electrode unit 16b, and the negative electrode unit 18b are arranged in this order. Has been placed. The positive electrode units 16a and 16b are connected to each other and connected to the external connection terminal 28, and the negative electrode units 18a and 18b are connected to each other and connected to the external connection terminal 30.

  In the embodiment of FIG. 3B, the positive electrode units 16a and 16b are arranged adjacent to each other, the negative electrode units 18a and 18b are arranged adjacent to each other, and the positive electrode units 16a and 16b are connected to each other. Connected to the external connection terminal 28, the negative electrode units 18 a and 18 b are connected to each other and connected to the external connection terminal 30.

  Even when three or more positive electrode units 16 and negative electrode units 18 are disposed, they may be disposed in the same manner as in FIG. 3A or 3B and connected to the external connection terminals 28 and 30. In this way, the same number of electrode units can be connected to increase the capacitance of the capacitor.

  FIG. 4 shows an embodiment in which a parallel electrode plate structure with positive and negative alternating arrangements is used as the electrode arrangement.

  The electrode plates 20 constituting the electrode units 46 and 48 are those shown in FIGS. 1 (B) and 1 (C). Each of the electrode units 46 and 48 is such that such an electrode plate 20 is arranged and fixed in parallel with each other at a constant interval, for example, 4 mm, and the electrode plate 20 of the electrode unit 46 and the electrode plate 20 of the electrode unit 48 are alternately arranged. Are arranged at equal intervals, that is, at intervals of 2 mm. An electrolytic solution 14 is accommodated in the electrolytic solution tank 12. Since the circulation mechanism of the electrolyte solution 14 is the same as that of the embodiment of FIGS. 1 and 2, detailed illustration and description thereof will be omitted.

  In the electrode units 46 and 48, one end of the electrode plate 20 included in each unit is fixed to a connecting metal plate, for example, an aluminum plate by welding. In order to keep the distance between the electrode plates 20 constant, it is preferable that the electrode plates 20 are also fixed to the connecting metal plate, for example, an aluminum plate, by welding on the side surfaces of the electrode units 46 and 48. The electrode units 46 and 48 are electrically connected to each other by fixing at least one end thereof with a connecting metal plate, and the electrode plates 20 included in the electrode units 46 and 48 have the same potential. The structure of the electrode plate 20 is the same as that shown in FIG. 1D, and an activated carbon film is fixed on both surfaces of an aluminum substrate. It is preferable that the surface of the connecting metal plate that comes into contact with the electrolytic solution is covered with an insulating film.

  In each electrode unit 46, 48, the electrode plate 20 faces in the vertical direction, and the upper end surface of the electrode unit 46 is fixed in contact with the inner upper surface of the electrolytic solution tank 12. In order to fix the electrode unit 46 to the electrolyte bath 12, an electrode terminal 28 is provided on the upper end surface of the electrode unit 46 as in the embodiment of FIG. 1, and the electrode terminal 28 is the upper surface of the lid 13 of the electrolyte bath 12. Protruding from. A screw is formed on the electrode terminal 28, and the electrode unit 46 is fixed to the lid 13 by fixing the screw of the electrode terminal 28 with a nut outside the lid 13. The electrode unit 48 is disposed such that an end portion to which the electrode plate 20 is fixed is located at the lower end, and the electrode unit 48 is fixed at a position away from the inner bottom surface of the electrolyte bath 12 by the support member 26.

  The electrode terminal 30 of the electrode unit 48 is also disposed on the lid 13 of the electrolytic solution tank 12. The electrode terminals 28 and 30 on the lid 13 are external connection terminals that are connected to an external circuit during charging and discharging.

  In the above embodiment, the air outlet is provided on the electrolytic solution 14 in the electrolytic solution tank 12 by disposing the electrolytic solution discharge ports 15 a to 15 d at positions lowered from the upper end of the electrolytic solution tank 12. However, the electrolytic solution outlets 15a to 15d may be provided at the upper end of the electrolytic solution tank 12, so that the electrolytic solution tank 12 may be filled with the electrolytic solution 14 without providing such an air layer.

DESCRIPTION OF SYMBOLS 12 Electrolyte tank 14 Electrolyte 15a-15d Electrolyte discharge port 16 Electrode unit for positive electrodes 18 Electrode unit for negative electrodes 20 Electrode plate 28, 30 Electrode terminal 32a, 32b Pipe for electrolyte supply port 36 Circulation pump

Claims (5)

An electrolytic bath containing the electrolytic solution;
A positive electrode immersed in the electrolytic solution and including a plurality of electrodes and electrically connected to each other;
A negative electrode immersed in the electrolyte and including a plurality of electrodes and electrically connected to each other;
A reflux mechanism for refluxing the electrolyte so that the electrolyte moves in the space between the electrodes in both the positive electrode and the negative electrode;
An electric double layer capacitor. The positive electrode and the negative electrode are each configured as an electrode unit in which a plurality of electrodes are assembled, and the electrodes are electrically connected to each other in each electrode unit,
The electric double layer capacitor according to claim 1, wherein the positive electrode unit and the negative electrode unit are in contact with each other.   The positive electrode unit and the negative electrode unit are each arranged in a plurality of units in the electrolyte bath, the positive electrode units are electrically connected, and the negative electrode units are electrically connected. The electric double layer capacitor according to claim 2.   2. The electric double layer capacitor according to claim 1, wherein the positive electrode and the negative electrode are arranged such that the positive electrode and the negative electrode are alternately arranged so that each positive electrode and the negative electrode are adjacent to each other. The electrodes are arranged vertically;
The reflux mechanism is discharged from an electrolyte supply port disposed below the electrode at the bottom of the electrolyte bath, an electrolyte discharge port provided at the top of the electrolyte bath, and the electrolyte discharge port. The electric double layer capacitor according to any one of claims 1 to 4, further comprising a circulation pump for sending an electrolytic solution to the electrolytic solution supply port, wherein the electrolytic solution flows between the electrodes from bottom to top.

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