JP2016085900A - Electrode for redox flow battery and redox flow battery using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide: a novel electrode for a redox flow battery, which enables the enhancement of a battery performance of a redox flow battery, and enables an operation at low cost; and a redox flow battery using such an electrode.SOLUTION: An electrode for a redox flow battery comprises porous carbon forming a three dimension network structure and having open pores which open at least two positions in its surface. A redox flow battery 1 comprises: a positive electrode cell room 31 and a negative electrode cell room 32 including a positive electrode 4 and a negative electrode 5, each composed of the electrode for a redox flow battery, respectively; a diaphragm 2 for separating the positive electrode cell room 31 and the negative electrode cell room 32 from each other; a positive electrode circulation mechanism 6 for circulating and supplying a positive electrode electrolyte containing a positive electrode active material to the positive electrode cell room 31; and a negative electrode circulation mechanism 7 for circulating and supplying a negative electrode electrolyte containing a negative electrode active material to the negative electrode cell room 32.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an electrode used in a redox flow battery and a redox flow battery using the electrode.

  The introduction of renewable energy such as solar power and wind power is being promoted. Since these power generation amounts are affected by the weather and the like, the introduction of a large amount of renewable energy causes a problem that it is difficult to stabilize the power supply amount. As a countermeasure against this problem, it is necessary to install a large-capacity storage battery to save excess power, level load, and the like.

  In recent years, redox flow batteries are expected as large-capacity storage batteries. The redox flow battery includes a positive electrode cell chamber including a positive electrode, a negative electrode cell chamber including a negative electrode, a diaphragm positioned between the positive electrode cell chamber and the negative electrode cell chamber, and a positive electrode cell chamber and a negative electrode cell chamber. A circulation mechanism for supplying each of an electrolytic solution containing an active material and an electrolytic solution containing a negative electrode active material.

  In such a redox flow battery, an electrolytic solution is circulated in each of the positive electrode cell chamber and the negative electrode cell chamber, and the redox reaction of the positive electrode active material and the negative electrode active material in each of the positive electrode in the positive electrode cell chamber and the negative electrode in the negative electrode cell chamber. As a result, charging / discharging is performed.

  The positive electrode and the negative electrode are places where an oxidation-reduction reaction of the active material in the electrolytic solution is generated, and it is required to efficiently generate the oxidation-reduction reaction of the active material. In general, it is composed of an excellent porous material. Conventionally, carbon felt, carbon paper, carbon cloth, and the like have been used as electrodes for redox flow batteries.

JP 2013-65530 A

  As described above, the positive electrode and the negative electrode in the redox flow battery are places that cause an oxidation-reduction reaction of the active material in the electrolytic solution. Therefore, in order to improve the battery performance (charge / discharge performance) in the redox flow battery, the characteristics of the positive electrode and the negative electrode are large in the area where the electrolyte solution can be contacted and have an affinity (hydrophilicity) for the electrolyte solution. High is required. If the battery performance in the redox flow battery is improved, the redox flow battery can be operated at a low cost.

  However, in the carbon felt used as the conventional positive electrode and negative electrode, there is a limit in increasing the surface area and improving the affinity for the electrolytic solution. Moreover, since the carbon felt has a thickness of 2 to 5 mm, the designed output density of the positive electrode cell chamber and the negative electrode cell chamber is lowered. Furthermore, the carbon felt itself is an expensive material. Therefore, it is desired to propose a new electrode material that can improve the battery performance of the redox flow battery and can be operated at a lower cost.

  In view of the above problems, the present invention provides a novel redox flow battery electrode capable of improving battery performance in a redox flow battery and enabling operation at a low cost, and a redox flow battery using the same. For the purpose.

  In order to solve the above-mentioned problems, the present invention provides an electrode for a redox flow battery, comprising porous carbon, wherein the porous carbon has open pores that open at least at two locations on the surface of the porous carbon. And the electrode for redox flow batteries characterized by having comprised the three-dimensional network structure is provided (invention 1).

  According to the said invention (invention 1), the electrode for redox flow batteries used the said electrode by including the porous carbon which has the open pore which opens in at least two places of the surface, and makes | forms a three-dimensional network structure. The battery performance in the redox flow battery can be improved, and since it is not necessary to use a conventional expensive carbon felt, it is possible to operate at a low cost.

  In the above invention (Invention 1), the porous carbon is produced by subjecting a mixture of a carbon precursor and template particles to a heat treatment to carbonize the carbon precursor, and then removing the template particles. The template particles are preferably alkaline earth metal oxides (Invention 2).

  According to the said invention (invention 2), since porous carbon can be manufactured using an inexpensive material and the electrode for redox flow batteries can be manufactured, the battery performance in the redox flow battery using the said electrode is improved. Can be operated at low cost.

  In the said invention (invention 1 and 2), the said porous carbon can be comprised in a sheet form (invention 3), In the said invention (invention 1-3), the said porous carbon and the said porous carbon are supported. (Invention 4) In this invention (Invention 4), a base fabric containing polymer fibers can be used as the substrate (Invention 5).

  In the said invention (invention 1-5), it is preferable to further contain resin which has an amide bond in a structural unit (invention 6), and it is preferable to contain resin which has an amide bond in the said structural unit as a binder (invention). 7) The resin having an amide bond in the structural unit is preferably at least one selected from the group consisting of polyamide, polyamideimide, polyimide precursor, and a resin mixture of polyimide and polyimide precursor (Invention 8). ).

  The present invention also includes a positive electrode cell chamber and a negative electrode cell chamber each including a positive electrode and a negative electrode made of a redox flow battery electrode according to the above inventions (Inventions 1 to 8), the positive electrode cell chamber and the negative electrode cell chamber. A separation membrane; a positive electrode circulation mechanism that circulates and supplies a positive electrode electrolyte containing a positive electrode active material to the positive electrode cell chamber; and a negative electrode circulation mechanism that circulates and supplies a negative electrode electrolyte containing a negative electrode active material to the negative electrode cell chamber. A redox flow battery is provided (Invention 9).

  ADVANTAGE OF THE INVENTION According to this invention, the battery performance in a redox flow battery can be improved, and the novel redox flow battery electrode using the same for the operation | movement at low cost and it can be provided.

FIG. 1 is a schematic configuration diagram illustrating a redox flow battery according to an embodiment of the present invention. FIG. 2 is an exploded perspective view showing a single cell configuration of a redox flow battery according to an embodiment of the present invention. FIG. 3 is an SEM image of the porous carbon produced in Example 1. FIG. 4 is a TEM image of the porous carbon produced in Example 1.

Embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic configuration diagram illustrating a redox flow battery according to the present embodiment, and FIG. 2 is an exploded perspective view illustrating a single cell configuration of the redox flow battery according to the present embodiment.

  As shown in FIG. 1, the redox flow battery 1 according to the present embodiment circulates a positive electrode electrolyte in a cell chamber 3 including a positive electrode cell chamber 31 and a negative electrode cell chamber 32 separated by a diaphragm 2, and the positive electrode cell chamber 31. A positive electrode circulation mechanism 6 to be supplied and a negative electrode circulation mechanism 7 to circulate and supply a negative electrode electrolyte to the negative electrode cell chamber 32 are provided. The positive electrode cell chamber 31 includes the positive electrode 4, and the negative electrode cell chamber 32 includes the negative electrode 5.

  Examples of the positive electrode electrolyte of the redox flow battery 1 include an acidic aqueous solution (for example, an aqueous sulfate solution) containing metal ions (for example, vanadium ions, iron ions, manganese ions, etc.) as a positive electrode active material. Moreover, as a negative electrode electrolyte solution, acidic aqueous solution (for example, sulfate aqueous solution etc.) containing the metal ion (for example, vanadium ion, chromium ion, titanium ion, etc.) as a negative electrode active material is mentioned, for example. In particular, it is desirable to use an acidic aqueous solution (pH = 1 or so) containing vanadium ions as the positive electrode active material and the negative electrode active material as the positive electrode electrolyte and the negative electrode electrolyte.

  In the redox flow battery 1 using an aqueous solution containing vanadium ions as a positive electrode electrolyte and a negative electrode electrolyte, a battery reaction (oxidation-reduction reaction) represented by the following formula occurs in each of the positive electrode cell chamber 31 and the negative electrode cell chamber 32.

When the positive electrode reaction _{^{charge: VO 2+ + H 2 O →}} VO 2 + + 2H + + e - ... (1)
During discharge: VO ₂ ⁺ + 2H ⁺ + e ⁻ → VO ₂ ⁺ + H ₂ O (2)
Negative electrode reaction During charging: V ³⁺ + e ⁻ → V ²⁺ (3)
During discharge: V ²⁺ → V ³⁺ + e ⁻ (4)

  At the time of charging, as shown in the formulas (1) and (3), tetravalent vanadium ions are oxidized to pentavalent at the positive electrode to release electrons, and trivalent vanadium ions are reduced to divalent at the negative electrode. The On the other hand, at the time of discharge, as shown in formulas (2) and (4), divalent vanadium ions are oxidized to trivalent at the negative electrode to release electrons, and pentavalent vanadium ions are converted to tetravalent at the positive electrode. Reduced.

  Examples of the diaphragm 2 that separates the cell chamber 3 into the positive electrode cell chamber 31 and the negative electrode cell chamber 32 include, for example, vinyl chloride; fluororesin; polysulfone; resin such as polyethylene, polypropylene, and the like, and an ion exchange having an ion exchange group. An ion exchange membrane made of a resin can be used. Examples of the ion exchange group include a sulfonic acid group, a carboxylic acid group, a phosphonic acid group, a phosphinic acid group, a pyridinium base, a quaternary ammonium base, a tertiary amine group, and a phosphonium group.

The positive electrode 4 and the negative electrode 5 in the present embodiment include porous carbon having open pores opened at at least two locations on the surface and forming a three-dimensional network structure. As the positive electrode 4 and the negative electrode 5 contain porous carbon having such a structure, the battery utilization in the redox flow battery 1 can be improved, as will be apparent from the examples described later. Performance can be improved. Although the reason why the battery utilization rate in the redox flow battery 1 is improved by including the porous carbon in the positive electrode 4 and the negative electrode 5 is not clear, the porous carbon is made of other carbon materials (for example, acetylene black, kettle, etc.). In the positive electrode 4 and the negative electrode 5 containing the porous carbon, the active material is oxidized by the fact that the hydrophilicity is higher than that of the chain black and the like, and the electrolyte easily enters the inside through the open pores of the porous carbon. It is presumed that this is because the reaction field causing the reduction reaction increases. The battery utilization rate means the ratio (%) of the actual discharge time with respect to the theoretical capacity (the value converted from the vanadium concentration, the amount of the electrolytic solution and the current value into the discharge time) in the redox flow battery 1. Discharge time is in a range from the upper limit voltage V _max until the lower limit voltage V _min, the circulation supply amount of electrolytic solution is a constant flow rate, it means a time required when discharged continuously at a constant current.

The BET specific surface area of the porous carbon is preferably 600 to 1800 m ² / g. When the BET specific surface area of the porous carbon is within the above range, the battery utilization rate in the redox flow battery 1 including the positive electrode 4 and the negative electrode 5 including the porous carbon can be improved.

  The average particle diameter (arithmetic average particle diameter) of the porous carbon can be set to about 200 to 400 μm, for example. The average particle diameter can be measured using a laser diffraction / scattering particle size distribution measuring apparatus (for example, product name: LA-920 manufactured by HORIBA).

  The porous carbon is, for example, a mixture of carbon precursors (carbon raw materials) such as polyaniline resin, polyimide, petroleum-based tar pitch, acrylic resin, and template particles such as oxides of alkaline earth metals (Ca etc.). After carbonizing the carbon precursor (carbon raw material) by heat treatment at 600 to 2500 ° C. in a non-oxidizing atmosphere (nitrogen atmosphere or the like), the template particles are put into a sulfuric acid aqueous solution of several mol / L (for example, 1 mol / L). It can be produced by dissolving and removing. The porous carbon produced as described above is presumed to have the above structure (a three-dimensional network structure having open pores opened at at least two locations on the surface).

  Each of the positive electrode 4 and the negative electrode 5 only needs to contain at least the porous carbon, but preferably includes a binder that binds the plurality of porous carbons to each other. In the redox flow battery 1 according to the present embodiment, as the binder, even if a voltage (about 0.5 to 2 V) is applied in the positive electrode electrolyte and the negative electrode electrolyte, which are acidic aqueous solutions having a pH of about 1 to 2. Resin having an amide bond in the structural unit (for example, polyamide, polyamideimide, polyimide precursor (polyamic acid), resin mixture of polyimide and polyimide precursor (polyamic acid), etc.) is preferable. It is more preferable to include at least one kind. Particularly preferably, at least one of polyamide, polyamideimide, polyimide precursor, and a resin mixture of polyimide and polyimide precursor is used alone, or two or more mixed resins are used as the binder.

  The content of the binder in the positive electrode 4 and the negative electrode 5 can be, for example, about 10 to 85% by mass with respect to the total mass of the porous carbon and the binder. When the content of the binder is less than 10% by mass, the binding force in the positive electrode 4 and the negative electrode 5 is insufficient and the content of the carbon particles is reduced, thereby reducing the reaction field that causes the redox reaction. Therefore, the battery utilization rate may be reduced. On the other hand, when the content of the binder exceeds 85% by mass, the exposed surface area of the carbon particles contained in the positive electrode 4 and the negative electrode 5 (the area where the positive electrode electrolyte and the negative electrode electrolyte can be contacted) is reduced to oxidize. While the reaction field that causes the reduction reaction is reduced, the electrical resistance of the positive electrode 4 and the negative electrode 5 is increased, and the battery utilization rate may be reduced.

  When a resin mixture of polyimide and a polyimide precursor (polyamic acid) is used as the binder, the content ratio of the polyimide and the polyimide precursor (polyamic acid) in the binder is such that the positive electrode electrolyte with respect to the carbon particle surface and It can be appropriately set within a range that does not lower the affinity of the negative electrode electrolyte.

  The content ratio between the polyimide and the polyimide precursor (polyamic acid) in the binder can be adjusted in the production process of the positive electrode 4 and the negative electrode 5. In the present embodiment, the positive electrode 4 and the negative electrode 5 are prepared by preparing an electrode-forming slurry containing carbon particles and a binder, applying the electrode-forming slurry to a porous sheet substrate or the like, which will be described later, and drying. Can be made. In this production process, for example, the electrode forming slurry is applied on the porous sheet substrate, and heated under heating conditions (heating temperature, heating time, etc.) that can promote imidization of the polyimide precursor (polyamic acid), The content ratio can be adjusted by removing the solvent and binding the carbon particles on the porous sheet substrate while imidizing the polyimide precursor (polyamic acid). Moreover, the slurry for electrode formation containing the resin mixture of the polyimide of the desired content ratio and a polyimide precursor (polyamic acid) is prepared, the said slurry is apply | coated on a porous sheet base material, and a polyimide precursor (polyamic acid) Is heated under heating conditions (heating temperature, heating time, etc.) that do not imidize, and without imidizing the polyimide precursor (polyamic acid), the solvent is removed and the carbon particles are placed on the porous sheet substrate. The content ratio can be adjusted by binding.

  Moreover, the positive electrode 4 and the negative electrode 5 are, for example, a base fabric such as a woven fabric or a nonwoven fabric including polymer fibers such as polyphenylene sulfide fiber, polyamideimide fiber, polyphenylene ether fiber, and polyethylene terephthalate fiber, a porous resin sheet, and the like. It is preferable to include a porous sheet substrate that supports the porous carbon. The porous carbon may be supported on one surface of the porous sheet substrate, or may be supported on both surfaces.

  As such a porous sheet substrate, it is more preferable to use a base fabric (woven fabric or non-woven fabric) containing the polymer fiber. By using the above-mentioned base fabric as the porous sheet base material, the thickness of the positive electrode 4 and the negative electrode 5 can be reduced as compared with the conventional carbon felt while maintaining sufficient electrochemical performance and strength.

The air permeability of the porous sheet substrate can be set to, for example, about ²⁰ to 150 cm ³ / sec / cm ² , preferably about ³⁰ to 130 cm ³ / sec / cm ² . Moreover, the fabric weight of the base fabric (woven fabric, non-woven fabric) as the porous sheet substrate can be set to, for example, about 15 to 150 g / m ² , preferably about 15 to 85 g / m ² . When the air permeability of the porous sheet base material and the basis weight of the base fabric are within the above ranges, for example, when porous carbon is supported on one surface of the porous sheet base material, The electrolyte solution easily penetrates from the other surface side, and the porous carbon and the electrolyte solution (active material) can be effectively brought into contact with each other. Further, for example, when porous carbon is supported on both surfaces of the porous sheet base material, the porous carbon on one side and the porous carbon on the other side are continuous, so that the positive electrode 4 and the negative electrode 5 It is possible to achieve electrical conduction in each thickness direction. In addition, the thickness of a porous sheet base material (base fabric) can be set to about 20-200 micrometers. The air permeability of the porous sheet substrate (in particular, the base fabric (woven fabric, non-woven fabric)) can be measured according to, for example, JIS L 1096 “Fabric and Knitted Fabric Test Method”.

  The thicknesses of the positive electrode 4 and the negative electrode 5 are not particularly limited, but if the thickness is small, the thickness of the positive electrode cell chamber 31 and the negative electrode cell chamber 32 can be reduced, and the unit volume of the redox flow battery 1 can be reduced. The output per hit can be increased. The thickness can be set to about 100 to 500 μm, for example.

  The positive electrode circulation mechanism 6 and the negative electrode circulation mechanism 7 are respectively provided with electrolyte tanks 61 and 71 that store the positive electrode electrolyte and the negative electrode electrolyte, respectively, and the electrolyte tanks 61 and 71, the positive electrode cell chamber 31, and the negative electrode cell chamber 32. The liquid supply pipes 63 and 73 and the drainage pipes 64 and 74 communicated with each other, and the pumps 62 and 72 provided in the middle of the liquid supply pipes 63 and 73 are provided.

  The redox flow battery 1 according to the present embodiment can be used as a form called a cell stack in which a plurality of single cells including the positive cell chamber 31, the diaphragm 2, and the negative cell chamber 32 are stacked. Specifically, as shown in FIG. 2, the redox flow battery 1 includes a laminate in which a bipolar plate 11A, a frame 12A having an opening, a diaphragm 2, a frame 12B having an opening, and a bipolar plate 11B are repeatedly laminated in this order. The structure is sandwiched by end plates from both ends in the stacking direction, and a positive electrode 4 and a negative electrode 5 are provided in the openings of the frames 12A and 12B. Each of the positive electrode cell chamber 31 and the negative electrode cell chamber 32 is constituted by the bipolar plates 11A and 11B, the frames 12A and 12B, and the diaphragm 2. Each of the positive electrode cell chamber 31 and the negative electrode cell chamber 32 is provided with a liquid supply port and a liquid discharge port (not shown) for supplying and discharging the positive electrode electrolyte and the negative electrode electrolyte, respectively. . The bipolar plates 11A and 11B of the positive electrode cell chamber 31 and the negative electrode cell chamber 32 are made of, for example, graphite, glassy carbon, plastic carbon (what kneaded carbon into plastic), and the frames 12A and 12B are made of, for example, , Vinyl chloride resin, polyethylene, Teflon (registered trademark), and the like.

  According to the redox flow battery 1 according to the present embodiment having the above-described configuration, the positive electrode 4 and the negative electrode 5 as redox flow battery electrodes have open pores that open at least at two locations on the surface. Since the porous carbon having a three-dimensional network structure is included, the battery utilization rate can be improved as compared with the conventional redox flow battery using carbon felt or the like as the electrode. In addition, the positive electrode 4 and the negative electrode 5 as redox flow battery electrodes may be manufactured at a lower cost than conventional carbon felts, and the redox flow battery 1 can be operated at a low cost.

  The embodiment described above is described for facilitating understanding of the present invention, and is not described for limiting the present invention. Therefore, each element disclosed in the above embodiment is intended to include all design changes and equivalents belonging to the technical scope of the present invention.

  In the above embodiment, the redox flow battery electrodes (the positive electrode 4 and the negative electrode 5) have been described with reference to an example in which porous carbon is supported on a porous sheet substrate via a binder. The present invention is not limited to such an embodiment. For example, the electrode for a redox flow battery does not include a porous sheet base material, and may be formed into a sheet shape by pressing a mixture of porous carbon and a binder. .

  The redox flow battery electrode may not include a binder and a porous sheet substrate. In this case, for example, a mixture of a carbon precursor and template particles is applied to the surfaces of the bipolar plates 11A and 11B on the positive electrode cell chamber 31 and negative electrode cell chamber 32 side, and the carbon precursor is carbonized. The porous carbon may be directly provided on the surfaces of the bipolar plates 11A and 11B on the side of the positive electrode cell chamber 31 and the negative electrode cell chamber 32 by dissolving them in a sulfuric acid aqueous solution or the like.

  In the above-described embodiment, an example in which a resin having an amide bond in a structural unit is used as a binder has been described as an example. However, the present invention is not limited to such an embodiment, and an electrode for a redox flow battery. (Positive electrode 4 and negative electrode 5) should just contain resin which has an amide bond in a structural unit. For example, at least one resin having an amide bond in the structural unit and other resins (for example, a resin having an amide bond in the structural unit such as polyvinylidene fluoride (PVDF), styrene-butadiene rubber (SBR)). A resin mixture with a resin having a low affinity for) may be included as a binder.

  Moreover, you may use resin which does not have an amide bond in a structural unit like the said PVDF, SBR, etc. as a binder. In this case, a resin having an amide bond in the structural unit is used as a surface treatment agent for the carbon particles. For example, a solution of a resin having an amide bond in a structural unit and carbon particles are mixed, the resin is attached to a part of the surface of the carbon particles, and the carbon particles to which the resin is attached are used for a redox flow battery. An electrode may be produced. Further, a redox flow battery electrode including carbon particles and a resin having no amide bond in a structural unit as a binder is manufactured, and a resin having an amide bond in a structural unit on the electrode surface (carbon particle surface). The resin having an amide bond in the structural unit may be attached to the carbon particle surface by applying or spraying the above solution.

  EXAMPLES Hereinafter, although an Example etc. are given and this invention is demonstrated further in detail, this invention is not limited to the following Example etc. at all.

[Example 1]
<Preparation of porous carbon>
Polyaniline resin as a carbon precursor and calcium oxide particles (average particle size of 5 μm) as template particles were mixed at a mass ratio of 1: 1. Next, the obtained mixture was subjected to a heat treatment at 1000 ° C. for 1 hour in a nitrogen atmosphere, and the polyaniline resin was thermally decomposed to be carbonized. Finally, the obtained carbide was washed with a sulfuric acid solution to elute CaO as template particles, thereby producing porous carbon. The BET specific surface area of the porous carbon was measured and found to be 1500 m ² / g.

  When the porous carbon produced as described above was imaged using SEM (manufactured by JEOL Ltd., JSM-6700F) and TEM (manufactured by Hitachi High-Technologies Corp., H-7650), it is shown in FIG. 3 and FIG. As described above, it was confirmed that the porous carbon had open pores opened at at least two places on the surface thereof and formed a three-dimensional network structure.

<Production of electrode>
The above porous carbon, a polyimide precursor (Ube Industries, U-varnish) as a binder, and N-methylpyrrolidone (NMP) are mixed, and an Excel auto homogenizer (Nippon Seiki Seisakusho) is used. The slurry for electrode formation was prepared by stirring for 3 minutes at a rotational speed of 6000 rpm (mass ratio of porous carbon and binder (polyimide precursor) = 1: 1).

  By applying the electrode-forming slurry to both sides of carbon paper (GDL10AA, manufactured by SGL) previously fired at 500 ° C. using an applicator (manufactured by Tester Sangyo) and drying at 120 ° C. for 30 minutes. A redox flow battery electrode (thickness: 400 μm) was prepared.

<Charge / discharge evaluation test>
The redox flow battery electrode produced as described above was used as the positive electrode 4 and the negative electrode 5, and a single cell for evaluation having the configuration shown in FIG. 2 (thickness of the positive electrode cell chamber: 0.3 μm, thickness of the negative electrode cell chamber) : 0.3 μm) and a charge / discharge evaluation test was performed. An aqueous vanadium sulfate solution (vanadium concentration 2M, sulfate radical concentration 4M) was used as the positive electrode electrolyte, and an aqueous vanadium sulfate solution (vanadium concentration 2M, sulfate radical concentration 4M) was used as the negative electrode electrolyte. As the diaphragm 2, a cation exchange membrane (manufactured by DuPont, Nafion (registered trademark) NRE-212) was used.

Then, charge / discharge evaluation was performed under the condition of a current density of 80 mA / cm ² while circulating and supplying the positive electrode electrolyte and the negative electrode electrolyte at 62 mL / min to each of the positive electrode cell chamber 31 and the negative electrode cell chamber 32 of the evaluation single cell. A test was conducted. As a result, the battery utilization rate was 83%.

[Example 2]
A redox flow battery electrode (thickness: 200 μm) and an evaluation single cell using the same in the same manner as in Example 1 except that a non-woven fabric made of polyphenylene sulfide fibers (Toray Industries, Torcon Paper) was used instead of carbon paper. And a charge / discharge evaluation test was performed. As a result, the battery utilization rate was 55%.

  In addition, when the resistance value ((ohm)) in the thickness direction of the redox flow battery electrode of Example 2 and the said nonwoven fabric was measured using the tester (made by CUSTOM, CDM-03D), it was for the redox flow battery of Example 2. The resistance value of the electrode was 5Ω, and the nonwoven fabric had a large resistance value and could not be measured. From this, it was confirmed that in the redox flow battery electrode of Example 2, electrical conduction was achieved in the thickness direction. This is because in the electrode for a redox flow battery produced by applying electrode forming slurry to both surfaces of the nonwoven fabric, carbon particles (electrode forming slurry) enter the nonwoven fabric, and the carbon particles on both surfaces are continuous with each other. It is considered that electrical conduction was achieved in the thickness direction of the redox flow battery electrode.

[Comparative Example 1]
<Charge / discharge evaluation test>
A redox flow battery electrode was prepared in the same manner as in Example 1 except that ketjen black (EC600JD, manufactured by Lion Corporation, specific surface area: 1270 m ² / g) was used instead of porous carbon. A single cell for evaluation was produced in the same manner as in Example 1 using the obtained electrode as a positive electrode and a negative electrode. And the charge / discharge evaluation test was done like Example 1 except having changed the current density into 20 mA / cm < ² >. As a result, the battery utilization rate was 50%.

[Comparative Example 2]
A single cell for evaluation was prepared in the same manner as in Comparative Example 1 except that carbon paper (GDL10AA, manufactured by SGL) subjected to a baking treatment at 500 ° C. was used as a redox flow battery electrode (positive electrode and negative electrode). Then, a charge / discharge evaluation test was conducted. As a result, the battery utilization rate was 52%.

  As is clear from the results of Example 1 and Comparative Example 2, by using the redox flow battery electrode containing porous carbon of Example 1, a redox flow using an electrode made of a conventional carbon felt, carbon paper, or the like. It has been confirmed that the battery utilization rate can be improved as compared with the battery. The reason why the battery utilization rate improved in the redox flow battery using the redox flow battery electrode of Example 1 is that the porous carbon having open pores opening at least two places on the surface and having a three-dimensional network structure, It is inferred that this is because the affinity for the electrolyte is high and the electrolyte easily enters the inside through the open pores of the porous carbon, thereby increasing the reaction field in the electrolyte and causing a redox reaction of the substance. . Therefore, it is considered that the charge / discharge characteristics of the redox flow battery, that is, the battery performance can be improved by using the electrode for redox flow battery containing the porous carbon of Example 1.

  Further, as is clear from the results of Example 2, by using a non-woven fabric made of polymer fibers as a porous sheet base material for supporting porous carbon, it is possible to use for a redox flow battery without reducing the battery utilization rate. Since the thickness of the electrode can be reduced, it is considered that the battery capacity per unit volume of the redox flow battery can be increased. Furthermore, a redox flow battery electrode can be manufactured at a lower cost than conventional carbon felts.

  Further, as is clear from the results of Example 1 and Comparative Example 1, the redox flow battery electrode containing porous carbon produced in Example 1 is used even for carbon particles having substantially the same specific surface area. Thus, it was confirmed that the battery utilization rate could be improved.

  From this, the porous carbon produced in Example 1 has a higher affinity for the electrolytic solution than the ketjen black used in Comparative Example 1, and thus the reaction field in which the redox reaction of the active material occurs can be further improved. It is assumed that it can be increased.

  The redox flow battery electrode of the present invention can be used as an electrode for a large-capacity storage battery for storing surplus power, load leveling, and the like due to the introduction of a large amount of renewable energy.

DESCRIPTION OF SYMBOLS 1 ... Redox flow battery 2 ... Diaphragm 31 ... Positive electrode cell chamber 32 ... Negative electrode cell chamber 4 ... Positive electrode (redox flow battery electrode)
5 ... Negative electrode (redox flow battery electrode)
6 ... Positive electrode circulation mechanism 7 ... Negative electrode circulation mechanism

Claims (9)

An electrode for a redox flow battery,
Contains porous carbon,
An electrode for a redox flow battery, wherein the porous carbon has open pores opened at at least two locations on the surface of the porous carbon and has a three-dimensional network structure. The porous carbon is produced by heat-treating a mixture of a carbon precursor and template particles to carbonize the carbon precursor, and then removing the template particles.
The redox flow battery electrode according to claim 1, wherein the template particle is an alkaline earth metal oxide.   The redox flow battery electrode according to claim 1, wherein the porous carbon is formed in a sheet shape.   The redox flow battery electrode according to any one of claims 1 to 3, comprising the porous carbon and a base material that supports the porous carbon.   The redox flow battery electrode according to claim 4, wherein the base material is a base fabric containing polymer fibers.   The redox flow battery electrode according to claim 1, further comprising a resin having an amide bond in the structural unit.   The redox flow battery electrode according to claim 6, wherein the structural unit includes a resin having an amide bond as a binder.   The resin having an amide bond in the structural unit is at least one selected from the group consisting of a polyamide, a polyamideimide, a polyimide precursor, and a resin mixture of polyimide and a polyimide precursor. 8. An electrode for a redox flow battery according to 7. A positive electrode cell chamber and a negative electrode cell chamber each including a positive electrode and a negative electrode made of the redox flow battery electrode according to claim 1;
A diaphragm separating the positive electrode cell chamber and the negative electrode cell chamber;
A positive electrode circulation mechanism for circulating and supplying a positive electrode electrolyte containing a positive electrode active material to the positive electrode cell chamber;
A redox flow battery comprising: a negative electrode circulation mechanism for circulating and supplying a negative electrode electrolyte containing a negative electrode active material to the negative electrode cell chamber.