JP2013065530A - Redox flow battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a redox flow battery (RF battery) with a low resistance and a high electric current efficiency.SOLUTION: The RF battery supplies an electrolytic solution to a battery element having a positive electrode 104, a negative electrode 105, and an ion-exchange membrane 10 interposed between the electrodes 104, 105 to perform charge and discharge. The ion-exchange membrane 10 has porous sheet materials 11A, 11B on faces opposed to the electrodes 104, 105; the porous sheet materials are formed from a material softer than a material constituting the electrodes 104, 105. The porous sheet materials 11A, 11B can prevent the ion-exchange membrane 10 from being damaged owing to the contact with the electrode 104, 105. In addition, the porous sheet materials 11A, 11B per se are soft and therefore, they never damage the ion-exchange membrane 10. The porous sheet materials 11A, 11B are hard to impede the ion conductivity and the permeability of the electrolytic solution. The RF battery of the invention can prevent the short circuit resulting from the damage to the ion-exchange membrane 10, and it achieves a high current efficiency and a low resistance.

Description

  The present invention relates to a redox flow battery. In particular, the present invention relates to a redox flow battery with low resistance and high current efficiency.

  In recent years, introduction of new energy such as solar power generation and wind power generation has been promoted worldwide as a countermeasure against global warming. Since these power generation outputs are affected by the weather, large-scale introduction of power generation using renewable energy causes a problem that it is difficult to maintain the frequency and voltage of the power system. As one of the countermeasures against this problem, it is expected to install a large-capacity storage battery to smooth the output fluctuation, save surplus power, and level the load.

  One of the large-capacity storage batteries is a redox flow battery (hereinafter referred to as an RF battery). The RF battery 100 is known in the form shown in FIG. The RF battery 100 supplies a battery element 100c having an ion exchange membrane 101 interposed between a positive electrode cell 102 incorporating a positive electrode 104 and a negative electrode cell 103 incorporating a negative electrode 105, and supplying an electrolytic solution to the battery element 100c. A circulation mechanism is provided, and the positive electrode electrolyte and the negative electrode electrolyte are circulated and supplied to the battery element 100c by the circulation mechanism to perform charge / discharge. The circulation mechanism includes a positive electrode tank 106 that stores the positive electrode electrolyte, positive electrode pipes 108 and 110 that distribute the positive electrode electrolyte between the positive electrode tank 106 and the battery element 100c, a negative electrode tank 107 that stores the negative electrode electrolyte, and a negative electrode tank. Negative electrode pipes 109 and 111 for flowing a negative electrode electrolyte between 107 and the battery element 100c, and pumps 112 and 113 arranged in the upstream pipes 108 and 109 are provided. As the electrolytic solution, typically, an aqueous solution containing metal ions such as vanadium ions whose valence changes by oxidation-reduction is used. In FIG. 3, the ions in the tanks 106 and 107 are illustrative. In FIG. 3, the solid arrow means charging, and the broken arrow means discharging.

  As the ion exchange membrane 101, a material in which an ion exchange resin is attached to a base material made of a resin such as vinyl chloride or polyethylene is widely used (Patent Document 1). The positive electrode 104 and the negative electrode 105 typically include a nonwoven fabric made of carbon fiber.

JP-A-10-172600

  It is desired to improve the battery efficiency (for example, current efficiency) of the RF battery while reducing the resistance.

  As a result of investigations by the present inventors, it has been found that in an RF battery with low current efficiency, the fibers constituting the electrode may pierce the ion exchange membrane. From this, the positive electrode electrolyte and the negative electrode electrolyte were mixed and short-circuited through the hole formed in the portion where the fiber pierced in the ion exchange membrane and the crack extending from the hole, resulting in a decrease in current efficiency. ,it is conceivable that. In addition, the portion where the fiber is pierced becomes a starting point of destruction, and there is a possibility that the life of the RF battery is shortened by the destruction of the ion exchange membrane such as the ion exchange resin dropping off.

  In order to prevent damage such as holes and cracks, for example, it is conceivable to increase the thickness of the ion exchange membrane (particularly the thickness of the ion exchange resin). However, in this case, the thick resin causes a decrease in ion conductivity and electrolyte permeability, resulting in an increase in electrical resistance and difficulty in reducing resistance.

  Even if the ion exchange membrane and the electrode can be laminated so that the fibers constituting the electrode are not pierced in the manufacturing stage, the constituent elements of the battery element expand and contract each time charging / discharging is performed. The contact point between the electrode and the electrode changes. Therefore, the ion exchange membrane can be damaged by contact with the electrode as described above.

  Therefore, it is desired to develop an RF battery that has low resistance and can improve current efficiency. In addition, it is desired to develop an RF battery that can maintain high current efficiency while maintaining low resistance over a long period of time.

  Therefore, an object of the present invention is to provide a redox flow battery with low resistance and high current efficiency.

  The present invention achieves the above object by disposing a cover made of a specific material between the ion exchange membrane and the electrode.

  The redox flow battery of the present invention: an RF battery is a secondary battery that is charged and discharged by supplying an electrolytic solution to a battery element comprising a positive electrode, a negative electrode, and an ion exchange membrane interposed between the two electrodes. It is a battery. In the ion exchange membrane, a porous sheet material made of a material softer than the constituent material of the positive electrode and the negative electrode is provided on a surface facing each of the positive electrode and the negative electrode.

  By interposing the porous sheet material between the ion exchange membrane and the positive electrode and between the ion exchange membrane and the negative electrode, in the RF battery of the present invention, the ion exchange membrane, the positive electrode, and the ion exchange Both the membrane and the negative electrode can be reduced from direct contact, preferably not substantially in contact. Therefore, the RF battery of the present invention can effectively reduce, and preferably prevent, cracks and holes in the ion exchange membrane due to contact with the electrodes. And since the said porous sheet material is comprised from the softer material than an electrode, a crack and a hole do not produce in an ion exchange membrane substantially by contact with the said porous sheet material. That is, the porous sheet material functions as a cover for preventing damage caused by the ion exchange membrane coming into contact with the positive electrode and the negative electrode, and effectively reduces local short-circuiting due to the generation of cracks and holes, or Can be prevented. Moreover, since the said porous sheet material is a porous body, it is hard to inhibit conduction of ion and the distribution | circulation of electrolyte solution. Thus, the RF battery of the present invention having the porous sheet material made of a specific material has low resistance and can improve current efficiency. In addition, the RF battery of the present invention can protect the ion exchange membrane with a porous sheet material not only in the manufacturing stage but also in repeated charge / discharge operations, and thus has a low resistance and a high current efficiency over a long period of time. Can be maintained.

  As one aspect of the present invention, the positive electrode and the negative electrode are composed of a carbon fiber non-woven fabric, and the porous sheet material is composed of one organic material selected from a fluororesin, a phenol resin, and an engineering plastic. The form which was made is mentioned. In particular, the fluororesin includes polytetrafluoroethylene: PTFE.

  When an electrode made of a carbon fiber non-woven fabric is used, generation of oxygen gas is easily suppressed as a side reaction of charge and discharge, and oxidation of the battery member based on the oxygen gas can be suppressed. Any of the organic materials listed above is softer than the carbon constituting the nonwoven fabric and has high resistance to the electrolyte used in the RF battery. Therefore, the above embodiment can construct an RF battery with low resistance and high efficiency. In particular, when the porous sheet material is made of PTFE, (1) very high resistance to the electrolyte, and can protect the ion exchange membrane over a long period of time, (2) a highly porous sheet material By providing a sheet material having a high porosity, there is an effect that there is almost no increase in resistance and a low-resistance RF battery can be obtained.

  As an embodiment of the present invention, the porous sheet material may have a porosity of 60% to 90% and a thickness of 50 μm to 150 μm.

  The above configuration can prevent a decrease in ion conductivity and electrolyte permeability while sufficiently preventing contact between the ion exchange membrane and the electrode, so that a low-resistance and high-efficiency RF battery can be constructed. Can do.

  The redox flow battery of the present invention has low resistance and high current efficiency.

It is sectional drawing which shows the outline of the battery element provided to this invention RF battery. It is a schematic block diagram of the cell stack provided in RF battery. It is explanatory drawing which shows the basic composition and the principle of operation of RF battery.

  Embodiments of the present invention will be described below with reference to the drawings. In the figure, the same reference numerals indicate the same names. In FIG. 1, the sizes of the constituent members are shown differently for easy understanding.

  The basic structure of the redox flow battery: RF battery of the present invention is the same as that of the conventional RF battery shown in FIG. 3 described above, and is characterized by battery elements (particularly, members interposed between electrodes). Hereinafter, an outline of the basic configuration of the RF battery will be described, and feature points will be described in detail.

[Overall structure]
The RF battery of the present invention is connected to a power generation unit (for example, a solar power generator, a wind power generator, other general power plants, etc.) and a load such as a power system or a consumer via an AC / DC converter. Then, charging is performed using the power generation unit as a power supply source, and discharging is performed using the load as a power supply target. Like the conventional RF battery 100 (FIG. 3), the RF battery of the present invention has a battery element 100c (FIG. 3) as a main component, tanks 106 and 107 (FIG. 3), pipes 108 to 111 (FIG. 3), pumps 112 and 113. Using the electrolytic solution circulation mechanism (FIG. 3), the positive and negative electrolyte solutions are circulated and supplied to the battery element 100c for charging and discharging.

  The battery element 100c uses a form called a cell stack in which a plurality of positive electrode cells 102 (FIG. 3), ion exchange membranes 101 (FIG. 3), and negative electrode cells 103 (FIG. 3) are stacked. For the cell stack 200, a frame 212 including a bipolar plate 211 shown in FIG. 2 is used. The bipolar plate 211 is provided with a positive electrode 104 and a negative electrode 105 on the front and back, respectively, and the frame 212 is formed on the outer periphery of the bipolar plate 211, and from the liquid supply holes 213 and 214 and the electrodes 104 and 105 for supplying the electrolyte to the electrodes 104 and 105. Drain holes 215 and 216 for discharging the electrolyte are provided. The cell stack 200 is repeatedly laminated in order of a frame 210 having a bipolar plate 211, a positive electrode 104, an ion exchange membrane 101, a negative electrode 105, a bipolar plate 211, and so on. Are assembled by tightening the end plate 220 with a fastening member 230 such as a long bolt. By laminating a plurality of frames 212, the liquid supply hole 213 (214) and the drainage hole 215 (216) form a flow path for the positive electrode electrolyte (negative electrode electrolyte), and the flow paths are connected to the pipes 108 to 111. (FIG. 3) as appropriate. The bipolar plate 211 may be made of plastic carbon, and the frame 212 may be made of resin such as vinyl chloride.

[Electrolyte]
In the RF battery of the present invention, positive electrode: iron ion, negative electrode: chromium ion, positive electrode and negative electrode: vanadium ion, and others, positive electrode: manganese ion, negative electrode: titanium, as a pair of metal ions used for positive and negative active materials Examples thereof include at least one metal ion selected from the group consisting of ions, vanadium ions, chromium ions, zinc ions, and tin ions. When the positive electrode active material is manganese ions, depending on the negative electrode active material, an RF battery having an electromotive force higher than that of all vanadium-based RF batteries can be obtained. Further, when the positive electrode contains manganese ions together with manganese ions, it is possible to suppress the precipitation of MnO ₂ accompanying the disproportionation reaction of Mn ³⁺ . It can also be set as the form which contains manganese ion and titanium ion in both a positive electrode and a negative electrode.

The electrolyte solution for each positive and negative electrode is preferably an aqueous solution containing at least one of sulfuric acid, phosphoric acid, nitric acid, sulfate, phosphate, and nitrate. In particular, those containing sulfate anions (SO ₄ ²⁻ ) are easy to use.

[electrode]
As the positive electrode 104 and the negative electrode 105, a nonwoven fabric made of carbon fiber: carbon felt can be used. More specifically, in a non-compressed state, the fiber diameter is about 5 μm to 10 μm, the porosity is about 90% to 95%, and the thickness is about 3 mm to 5 mm. When the electrodes 104 and 105 are laminated and tightened (compressed) as described above, the thickness and the porosity change depending on the degree of tightening, and the flow state of the electrolyte changes. It is preferable to select and adjust the porosity, thickness, and tightening degree so that a desired distribution state is obtained. As the electrodes 104 and 105, known and commercially available electrodes can be used as appropriate.

  In addition, the positive electrode 104 and the negative electrode 105 include (1) at least one metal selected from Ru, Ti, Ir, Mn, Pd, Au and Pt, and Ru, Ti, Ir, Mn, Pd, Au and A composite material containing at least one metal oxide selected from Pt (for example, a Ti substrate coated with Ir oxide or Ru oxide), (2) a carbon composite containing the composite material, (3 ) Dimensionally stable electrode (DSE) containing the above composite material, (4) conductive polymer (e.g., polymer material conducting electricity such as polyacetylene, polythiophene), (5) graphite, (6) vitreous carbon, (7) Conductive diamond, (8) conductive diamond-like carbon (DLC), and (9) woven fabric made of carbon fiber can be used.

  When the above-mentioned carbon felt is viewed microscopically, fibers are fuzzy on its surface. When this fuzzy fiber comes into contact with an ion exchange membrane described later, the ion exchange membrane may be pierced or broken. An RF battery including such a fluffy electrode is configured to include a porous sheet material described later, thereby reducing / preventing the above-described piercing and the like.

[Ion exchange membrane]
The ion exchange membrane 10 (FIG. 1) is a base material made of a resin such as vinyl chloride, fluororesin, polyolefin (for example, polyethylene: PE, polypropylene: PP), an ion exchange resin having an ion exchange group, or an ion exchange resin. And a composite resin of a matrix 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. As the ion exchange membrane 10 is thicker, damage (holes and the like) due to contact with the positive electrode 104 and the negative electrode 105 can be prevented, but an increase in electric resistance is caused, so that the thickness is preferably about 5 μm to 100 μm. As the ion exchange membrane 10, a known one or a commercially available one can be used as appropriate.

[Porous sheet material]
In the RF battery of the present invention, the point that the ion exchange membrane 10 includes the porous sheet materials 11A and 11B (FIG. 1) on the surface facing the positive electrode 104 and the surface facing the negative electrode 105 is the largest. Features.

  The porous sheet materials 11A and 11B are mainly composed of the resin held on the base material, with the ion exchange membrane 10 in contact with the positive electrode 104 and the negative electrode 105, and the fibers described above are pierced or cracked. It functions as a protective layer to prevent damage and destruction such as falling off. Further, the porous sheet materials 11A and 11B have such flexibility that they do not damage or destroy the ion exchange membrane 10 even if they themselves contact the ion exchange membrane 10. In addition, it is desirable that the porous sheet materials 11A and 11B do not hinder ion conduction (high ion conductivity) and hardly increase the flow resistance of the electrolytic solution (excellent permeability of the electrolytic solution). From these points, it is assumed that the porous sheet materials 11A and 11B are made of a porous material and softer than the constituent materials of the electrodes 104 and 105. “Softer than the constituent material of the electrode” means that the constituent material itself of the porous sheet material is lower in hardness than the constituent material of the electrode itself. For example, a durometer can be used to measure the hardness of the porous sheet material.

  Specific materials of the porous sheet materials 11A and 11B include organic materials, and more specifically, fluororesins, phenol resins, and engineering plastics. The organic material is sufficiently soft as compared with carbon fibers listed as electrode materials, composites containing metals and metal oxides, carbon composites, graphite, diamond, DLC, and the like. Examples of the fluororesin include PTFE, a copolymer of tetrafluoroethylene and ethylene: ETFE, a tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer: PFA, and polyvinylidene fluoride: PVDF. Since the fluororesin has excellent resistance to an electrolytic solution such as a sulfuric acid solution, the ion exchange membrane 10 can be protected over a long period of time. Examples of the engineering plastic include polyether ether ketone: PEEK.

  Porous sheet materials 11A and 11B are woven fabrics and nonwoven fabrics using fibers of the above-mentioned organic materials, cut into sheet material, then expanded, and other fine pores are formed using known stretching processes Perforated sheets (for example, Poeflon (registered trademark of Sumitomo Electric Industries, Ltd.)), etc. having pores communicating linearly on the front and back of the sheet material (hereinafter referred to as straight holes), non-linear on the front and back Any one having pores communicating with each other (pores taking a bent path (hereinafter referred to as bent holes)) can be used. In addition, since the porous sheet materials 11A and 11B are softer than the constituent materials of the positive electrode 104 and the negative electrode 105, there are no fluffs on the surface like the above-mentioned woven fabrics and nets, and fibers such as non-woven fabrics are fluffy. In any form, the ion exchange membrane 10 is hardly damaged.

  The pore diameters of the porous sheet materials 11A and 11B depend on the form of the positive electrode 104 and the negative electrode 105. For example, when the electrodes 104 and 105 are made of a nonwoven fabric, the fibers constituting the nonwoven fabric are ion exchange membranes. It is preferable that the diameter is smaller than the fiber diameter so that it can be prevented from sticking into the fiber. However, if the pore diameter is too small, although depending on the porosity and the form of the sheet material, the permeability of the electrolytic solution is lowered and the internal resistance is increased. Therefore, the minimum diameter is preferably 1 nm or more. In a form having a straight hole such as a plain woven cloth or a net provided with a diamond-shaped hole, the electrolyte tends to permeate more easily than a form having a bent hole such as a non-woven cloth. Even so, there is a tendency that a decrease in permeability can be suppressed. On the other hand, if the pore diameter is too large, the ion exchange membrane 10 may be damaged, for example, the fibers constituting the electrode may pass through the pores and pierce the ion exchange membrane 10. Accordingly, the maximum diameter is preferably less than the minimum diameter of the fibers constituting the electrode. As described above, although depending on the porosity and the form of the sheet material, the average pore diameter is about 0.01 μm to 1 μm.

If the porosity of the porous sheet materials 11A and 11B is too small, that is, if the sheet material has few pores and a high density, the ion conductivity and the electrolyte permeability decrease, and the electrical resistance and internal resistance are reduced. Since it increases, depending on the thickness, it is preferably 50% or more, more preferably 60% or more, and particularly preferably 70% or more. If the porosity is too large, the strength is lowered due to the large number of pores, so 90% or less is preferable. The porosity of a nonwoven fabric can be measured using a mercury porosimeter, a gas adsorption specific surface area measuring apparatus, etc., for example. The porosity of the woven fabric or the above-mentioned porous sheet is, for example, using a value obtained by dividing the mass of the woven fabric per unit volume: D _p by the density of the fibers constituting the woven fabric: D _f (1− D _p / D _f ) × 100.

  When the porosity of the porous sheet material 11A, 11B is high, the ion conductivity and the electrolyte permeability can be sufficiently ensured, but usually the thicker the ion conductivity and the electrolyte permeability. Is preferably 150 μm or less. Depending on the porosity, it is more preferably 100 μm or less. If the thickness is too thin, the strength of the sheet material itself may decrease, and for example, the fibers constituting the electrode may break through the sheet material and further pierce the ion exchange membrane 10, which may damage the ion exchange membrane 10. . Accordingly, the thickness of the porous sheet materials 11A and 11B is preferably 50 μm or more, and more preferably 60 μm or more.

  At least one of the porous sheet materials 11A and 11B may be integrated with the ion exchange membrane 10 or simply laminated. When integrating the porous sheet material and the ion exchange membrane, for example, when integrating the ion exchange resin or composite resin and the base material, the porous sheet material is also integrated at the same time, or separately, For example, the composite resin is melted to join a porous sheet material.

<Test example>
The difference in battery characteristics with and without the porous sheet material was investigated.

In this test, each sample was prepared with an ion exchange membrane and electrode (carbon felt (average fiber diameter: 5 μm to 10 μm)) with the same specifications, and a single-cell RF battery with an electrode reaction area of 9 cm ² was prepared. did. A single cell battery is composed of battery elements each having a positive cell and a negative cell. As shown in FIG. 1, a positive electrode 104 and a negative electrode 105 are provided on both sides of one ion exchange membrane 10, respectively. The electrodes 104 and 105 are sandwiched by a frame 212 having a bipolar plate 211.

In Sample Nos. 1 to 3, porous sheet materials of the materials shown in Table 1 were arranged on both sides of the ion exchange membrane 10. Table 1 shows the thickness and porosity of the porous sheet material of each sample. As the porous sheet material of Sample Nos. 1 and 2, Poeflon (registered trademark of Sumitomo Electric Industries, Ltd.) was used. The porosity of Poreflon (registered trademark) was measured as follows. The mass per unit volume of Poreflon (registered trademark): D _po is determined. In addition, a sheet without pores is made of the same material as that of Poreflon (registered trademark), and the mass per unit volume of the sheet without holes: D _s is obtained. Then, (1−D _po / D _s ) × 100 is defined as the porosity by using the value obtained by dividing PoFlon (registered trademark) D _po by D _s of the non-porous sheet. In addition, the average pore diameter of Poreflon (registered trademark) of Sample Nos. 1 and 2 was 1 μm to 10 μm, and was obtained by measurement of pore diameter distribution. In sample No. 3, a porous sheet material of a different material was disposed on each surface of the ion exchange membrane. Specifically, the same Poreflon (registered trademark) as Sample No. 1 was placed on one side, and the woven fabric shown in Table 1 was placed on the other side. Sample No. 100 was a sample in which a porous sheet material was disposed only on one side of the ion exchange membrane, and the same Poraflon (registered trademark) as Sample No. 1 was disposed. In addition, a porosity, a hole diameter, and thickness are the values measured in the state which has not compressed the porous sheet material.

A vanadium solution was used as the positive electrode electrolyte and the negative electrode electrolyte, and the single cell batteries of each sample thus prepared were charged / discharged at a constant current of 70 mA / cm ² . In this test, when a predetermined switching voltage set in advance was reached, switching from charging to discharging was performed, and charging and discharging were performed for a plurality of cycles. After charging and discharging, the current efficiency and electrical resistance were determined for each sample. Current efficiency is (total discharge time / total charge time) x 100, and battery resistance (cell resistance) is the average voltage / average current in any one cycle among multiple cycles. did.

  As shown in Table 1, by providing a porous sheet material made of a material softer than the electrode on both surfaces of the ion exchange membrane facing the positive electrode and the negative electrode, current efficiency is suppressed while suppressing an increase in electrical resistance. It can be seen that can be improved.

  After charging and discharging, each sample was disassembled and the ion exchange membrane was observed by SEM. As a result, in sample No. 100, it was confirmed that the carbon fibers constituting the electrode were stuck into the ion exchange membrane. In Sample Nos. 1 to 3, it was not possible to confirm that the carbon fiber was stuck into the ion exchange membrane. From this, it is considered that the porous sheet material arranged on both sides of the ion exchange membrane prevented the ion exchange membrane from being damaged by contacting the electrode, thereby preventing a local short circuit. In addition, from this, it can be expected that damage such as part of the ion exchange resin dropping off due to contact with the electrode can be prevented, and the life of the ion exchange membrane can be extended, and thus the life of the RF battery can be extended. Is done.

  Further, the defective rate of the RF battery of sample No. 1,100 was examined. Specifically, after the RF battery was fabricated, it was disassembled without performing a charge / discharge operation, and the presence or absence of damage such as a hole or a crack was examined on the ion exchange membrane, and the damaged one was determined to be defective. As a result, in sample No. 100, damage to the ion exchange membrane was observed for three of the six batteries produced, but in sample No. 1, all of the six batteries produced were damaged. Was not seen. For this reason, it is expected that the defective rate of the RF battery can be reduced and the productivity can be improved by providing the porous sheet material on both sides of the ion exchange membrane.

  In addition, since the porous sheet material is provided on both sides of the ion exchange membrane, the ion exchange membrane can be sufficiently prevented from being damaged or destroyed by contact with the electrode. For example, the distribution pressure of the electrolyte is further increased. be able to. Although the pressure in the battery element is increased by the increase of the flow pressure, the ion exchange membrane is protected by the porous sheet material on both sides thereof, so that there is little or no risk of damage due to the increase of the pressure. By increasing the flow pressure, for example, an effect of suppressing liquid transfer (a phenomenon in which the electrolyte solution of one electrode moves to the other electrode) can be expected.

  The present invention is not limited to the above-described embodiment, and can be appropriately changed without departing from the gist of the present invention. For example, the material, thickness, porosity, pore diameter, electrode material, and the like of the porous sheet material can be appropriately changed.

  The redox flow battery of the present invention has a large capacity for the purpose of stabilizing fluctuations in power generation output, storing electricity when surplus of generated power, load leveling, etc., for power generation of new energy such as solar power generation and wind power generation. It can utilize suitably for a storage battery. In addition, the redox flow battery of the present invention can be suitably used as a large-capacity storage battery that is installed in a general power plant or factory, for the purpose of instantaneous voltage drop / power failure countermeasures and load leveling.

10 Ion exchange membrane 11A, 11B Porous sheet material
100 Redox flow battery 100c Battery element 101 Ion exchange membrane
102 Positive electrode cell 103 Negative electrode cell 104 Positive electrode 105 Negative electrode
106 Positive tank 107 Negative tank 108,110 Positive piping 109,111 Negative piping
112,113 pump
200 Cell stack 211 Bipolar plate 212 Frame 213,214 Supply hole
215,216 Drain hole 220 End plate 230 Tightening member

Claims (4)

A redox flow battery that performs charging and discharging by supplying an electrolytic solution to a battery element comprising a positive electrode, a negative electrode, and an ion exchange membrane interposed between the two electrodes.
The ion exchange membrane includes a porous sheet material made of a material softer than the constituent material of the positive electrode and the negative electrode, on a surface facing each of the positive electrode and the negative electrode. Redox flow battery. The positive electrode and the negative electrode are composed of a carbon fiber nonwoven fabric,
2. The redox flow battery according to claim 1, wherein the porous sheet material is composed of one organic material selected from a fluororesin, a phenol resin, and an engineering plastic.   3. The redox flow battery according to claim 1, wherein the porous sheet material has a porosity of 60% to 90% and a thickness of 50 μm to 150 μm. The positive electrode and the negative electrode are composed of a carbon fiber nonwoven fabric,
4. The redox flow battery according to claim 1, wherein the porous sheet material is made of polytetrafluoroethylene.

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