Current collecting structure for redox flow battery, redox flow battery cell, and redox flow battery system

Abstract

A current collector structure for redox flow batteries, the current collector structure being provided with a conductive member, an intervening member and a current collector member, which are sequentially superposed on one surface of a positive electrode or a negative electrode, wherein: the intervening member is a porous body that is configured from a composite material which contains a first conductive material and a second conductive material; the standard electrode potential of the first conductive material is closer to the standard electrode potential of the conductive member than to the standard electrode potential of the current collector member; and the standard electrode potential of the second conductive material is closer to the standard electrode potential of the current collector member than to the standard electrode potential of the conductive member.

Description

[Technical Field]

[0001] The present disclosure relates to a current collecting structure for a redox flow battery, a redox flow battery cell, and a redox flow battery system. This application claims priority based on Japanese Patent Application No. 2021-089491 filed on May 27, 2021, and incorporates by reference all of the contents of said Japanese application. [Background technology]

[0002] Patent Documents 1 and 2 disclose a current collecting structure for a battery for inputting and outputting electricity between a battery cell of a redox flow battery and an external device. The current collecting structure includes an end bipolar plate, a cushion material, and a current collecting plate, which are stacked in this order on one surface of a positive electrode or a negative electrode. Patent Document 1 describes that the surface of the end bipolar plate facing the cushion material is provided with a metal layer consisting of a thermally sprayed layer of tin, and the cushion material is composed of copper mesh. Patent Document 2 describes that the surface of the current collecting plate facing the cushion material is provided with a current collecting plate coating layer consisting of a layer of carbon material, and the cushion material contains carbon material. Hereinafter, the end bipolar plate will be referred to as the conductive member, the cushion material will be referred to as the interposing member, and the current collecting plate will be referred to as the current collecting member. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-119288 [Patent Document 2] Japanese Patent Application Laid-Open No. 2015-079738 Summary of the Invention

[0004] The current collecting structure for a redox flow battery according to the present disclosure comprises: A current collecting structure for a redox flow battery, comprising a conductive member, an interposing member, and a current collecting member stacked in this order on one surface of a positive electrode or a negative electrode, the interposing member is a porous body made of a composite material including a first conductive material and a second conductive material, a standard electrode potential of the first conductive material is closer to a standard electrode potential of the conductive member than to a standard electrode potential of the current collecting member; The standard electrode potential of the second conductive material is closer to the standard electrode potential of the current collecting member than to the standard electrode potential of the conductive member.

[0005] The redox flow battery cell of the present disclosure comprises: The current collecting structure for a redox flow battery according to the present disclosure is provided.

[0006] The redox flow battery system of the present disclosure comprises: The redox flow battery cell of the present disclosure is provided. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a schematic configuration diagram of a redox flow battery system according to an embodiment. [Figure 2] FIG. 2 is a schematic diagram of a cell stack including a current collecting structure for a redox flow battery according to the embodiment. [Figure 3] FIG. 3 is a schematic diagram illustrating an example of an interposition member included in the current collecting structure for a redox flow battery according to the embodiment. [Figure 4] FIG. 4 is a partially enlarged view of the intervening member shown in FIG. [Figure 5] FIG. 5 is a partially enlarged view showing a modified example of the interposition member shown in FIG. [Figure 6] FIG. 6 is a schematic diagram showing another example of the interposition member included in the current collecting structure for a redox flow battery according to the embodiment. [Figure 7] FIG. 7 is a schematic diagram showing yet another example of the interposition member included in the current collecting structure for a redox flow battery according to the embodiment. [Figure 8] FIG. 8 is a schematic diagram showing an example of a wire material constituting an interposition member included in a current collecting structure for a redox flow battery according to an embodiment. [Figure 9] FIG. 9 is a schematic cross-sectional view showing another example of a wire constituting an interposition member included in the current collecting structure for a redox flow battery according to the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0008] [Problem to be solved by this disclosure] In a current collecting structure including an interposed member, it is desired to suppress the occurrence of galvanic corrosion with a simple configuration even if moisture penetrates between the conductive member and the current collecting member.

[0009] An object of the present disclosure is to provide a current collecting structure for a redox flow battery that can suppress corrosion between a conductive member and a current collecting member with a simple configuration.Another object of the present disclosure is to provide a redox flow battery cell and a redox flow battery system that can suppress corrosion between a conductive member and a current collecting member with a simple configuration.

[0010] [Effects of this disclosure] The current collecting structure for a redox flow battery, the redox flow battery cell, and the redox flow battery system according to the present disclosure can suppress corrosion between the conductive member and the current collecting member with a simple configuration.

[0011] [Description of the embodiments of the present disclosure] First, embodiments of the present disclosure will be listed and described.

[0012] (1) A current collecting structure for a redox flow battery according to one embodiment of the present disclosure includes: A current collecting structure for a redox flow battery, comprising a conductive member, an interposing member, and a current collecting member stacked in this order on one surface of a positive electrode or a negative electrode, the interposing member is a porous body made of a composite material including a first conductive material and a second conductive material, a standard electrode potential of the first conductive material is closer to a standard electrode potential of the conductive member than to a standard electrode potential of the current collecting member; The standard electrode potential of the second conductive material is closer to the standard electrode potential of the current collecting member than to the standard electrode potential of the conductive member.

[0013] In the current collecting structure for a redox flow battery of the present disclosure, the first conductive material and the second conductive material constituting the interposed member each have a specific potential, thereby suppressing corrosion between the conductive member and the current collecting member. This is because corrosion is less likely to occur between the first conductive material and the conductive member, and corrosion is less likely to occur between the second conductive material and the current collecting member, thereby suppressing the occurrence of galvanic corrosion compared to when the interposed member is composed of only the first conductive material or the second conductive material. The current collecting structure for a redox flow battery of the present disclosure can utilize known conductive members and current collecting members. As described above, the current collecting structure for a redox flow battery of the present disclosure can suppress corrosion between the conductive member and the current collecting member with a simple configuration.

[0014] In the current collecting structure for a redox flow battery disclosed herein, the intervening member provided between the conductive member and the current collecting member is a porous body. When the porous body has elastic deformability, good electrical connection between the conductive member and the current collecting member can be ensured even if the pressure inside the battery cell constituting the redox flow battery changes. This is because even if the distance between the conductive member and the current collecting member changes due to a pressure change inside the battery cell, the intervening member deforms in response to the change.

[0015] (2) In the current collecting structure for a redox flow battery disclosed herein, a main component of the conductive material constituting the conductive member is carbon; The current collecting member may be mainly composed of copper or nickel.

[0016] According to the configuration (2), practical materials for the conductive member and the current collecting member are readily available.

[0017] (3) In the current collecting structure for a redox flow battery according to the present disclosure described above in (2), the first conductive material is mainly composed of carbon; The second conductive material may be mainly composed of copper or nickel.

[0018] The interposing member in (3) has a small potential difference with respect to both the conductive member and the current collecting member. The interposing member in (3) has excellent conductivity. Therefore, the configuration in (3) can further suppress corrosion between the conductive member and the current collecting member, and more easily ensure good electrical connection between the conductive member and the current collecting member.

[0019] (4) In the current collecting structure for a redox flow battery disclosed herein, The intervening member may be a mixture of a plurality of wire materials including a wire material made of the first conductive material and a wire material made of the second conductive material.

[0020] The interposing member (4) tends to have a small potential difference with both the conductive member and the current collecting member. The interposing member (4) has excellent flexibility because it contains a mixture of wires made of different conductive materials. The interposing member with excellent flexibility tends to ensure good electrical connection between the conductive member and the current collecting member.

[0021] (5) In the current collecting structure for a redox flow battery disclosed herein, The intervening member is a plurality of particles of the first conductive material; an assembly of a plurality of wires made of the second conductive material; The plurality of particles may be dispersed and disposed on a surface of the aggregate that comes into contact with the conductive member.

[0022] The configuration (5) makes it easy to limit the position of the particles to a specific location relative to the aggregate. It also makes it easy to arrange an appropriate material that is resistant to corrosion on both the conductive member-side surface of the interposing member and the current-collecting member-side surface of the interposing member. In particular, by providing a surface of the aggregate on which particles are not dispersed and arranging that surface facing the current-collecting member, the potential difference between the current-collecting member and the interposing member can be made substantially zero.

[0023] (6) In the current collecting structure for a redox flow battery disclosed herein, The intervening member is a plurality of particles of the second conductive material; an assembly of a plurality of wires made of the first conductive material; The plurality of particles may be dispersed and disposed on a surface of the assembly that comes into contact with the current collecting member.

[0024] According to the configuration (6), it is easy to limit the position of the particles to a specific location relative to the aggregate. It is also easy to arrange an appropriate material that is resistant to corrosion on each of the surface of the intervening member facing the conductive member and the surface of the intervening member facing the current collecting member. In particular, by providing a surface of the aggregate on which particles are not dispersed and arranging that surface facing the conductive member, it is possible to make the potential difference between the conductive member and the intervening member substantially zero.

[0025] (7) In the current collecting structure for a redox flow battery according to the present disclosure described above in (4) to (6), At least some of the plurality of wires may be stranded wires formed by twisting together a plurality of wires.

[0026] According to the configuration (7), by including a wire material made of twisted wire, the gaps between adjacent wire materials tend to be smaller compared to when the multiple wire materials are made of only solid wires. According to the configuration (7), moisture is less likely to penetrate into the gaps, and as a result, moisture is less likely to penetrate into the interior of the intervening member. According to the configuration (7), corrosion between the conductive member and the current collecting member is more easily suppressed.

[0027] (8) In the current collecting structure for a redox flow battery according to the present disclosure described above in (4) to (7), At least some of the plurality of wires may have a plating layer on the surface of the core.

[0028] According to the configuration (8), by selecting the material of the plating layer, it is easy to impart desired properties to the wire, and therefore easy to impart desired properties to the interposed member. For example, if the plating layer is more flexible than the core of the wire, the plating layers can deform to increase the contact area, making it easier to ensure adhesion between the wires. In addition, if the plating layer has excellent conductivity, the conductivity of the wire is improved. If the plating layer has excellent corrosion resistance, the corrosion resistance of the wire is improved.

[0029] (9) In the current collecting structure for a redox flow battery according to the present disclosure described above in (8), a main component of one of the core portion and the plating layer is copper; The main component of the other of the core portion and the plating layer may be nickel.

[0030] A wire having a core mainly composed of copper and a plating layer mainly composed of nickel has good corrosion resistance.A wire having a core mainly composed of nickel and a plating layer mainly composed of copper has good corrosion resistance.

[0031] (10) In the current collecting structure for a redox flow battery disclosed herein, the interposing member includes an insulating filling portion provided in the pore of the porous body, The filling portion may be made of a polymer material.

[0032] According to the configuration (10), it is possible to prevent moisture from penetrating into the interposing member through the pores of the porous body. Therefore, according to the configuration (10), it is easier to prevent corrosion between the conductive member and the current collecting member. Since the filling portion is insulating, it is easy to select a material with high fluidity. A material with high fluidity easily increases the covering effect of the filling portion on the pores of the porous body, making it easier to prevent moisture from penetrating. In addition, since the filling portion is insulating, it is easy to obtain practical materials as the polymer material that constitutes the filling portion.

[0033] (11) In the current collecting structure for a redox flow battery disclosed herein, the interposing member includes a conductive filling portion provided in the pores of the porous body, The filling portion may be made of a composite material in which a plurality of conductive fillers are dispersed in a polymer material.

[0034] According to the configuration (11), it is possible to prevent moisture from penetrating into the interposing member through the pores of the porous body, and the conductive filler can ensure conductivity, thereby ensuring a better electrical connection between the conductive member and the current collecting member.

[0035] (12) A redox flow battery cell according to one aspect of the present disclosure includes the current collector structure for a redox flow battery according to any one of (1) to (11) above.

[0036] By including the current collector structure for a redox flow battery of the present disclosure, the redox flow battery cell of the present disclosure can suppress corrosion between the conductive member and the current collector member with a simple configuration.

[0037] (13) A redox flow battery system according to one aspect of the present disclosure includes the redox flow battery cell according to (12) above.

[0038] By including the redox flow battery cell of the present disclosure, the redox flow battery system of the present disclosure can suppress corrosion between the conductive member and the current collector member with a simple configuration.

[0039] [Details of Embodiments of the Present Disclosure] Specific examples of the current collector structure for a redox flow battery, the redox flow battery cell, and the redox flow battery system of the present disclosure will be described with reference to the drawings. Hereinafter, the redox flow battery may sometimes be referred to as an "RF battery". The same reference numerals in the drawings indicate the same or corresponding parts. Note that the present invention is not limited to these examples, and is defined by the claims, and is intended to include all modifications within the meaning and scope equivalent to the claims.

[0040] As shown in FIG. 1, an RF battery system 1 of an embodiment includes an RF battery cell 10 of the embodiment. One of the features of the RF battery system 1 and the RF battery cell 10 of the embodiment is that they include the current collector structure 100 for an RF battery of the embodiment shown in FIG. 2. Hereinafter, first, the RF battery system 1 and the RF battery cell 10 will be described, and then the current collector structure 100 for an RF battery will be described.

[0041] [RF Battery System] The basic configuration of an RF battery system 1 according to an embodiment will be described with reference to Fig. 1. The RF battery system 1 is one of electrolyte circulation type storage battery systems. The RF battery system 1 includes RF battery cells 10 and a circulation mechanism that circulates electrolyte through the RF battery cells 10. The RF battery system 1 charges and discharges the RF battery cells 10 while supplying electrolyte to them.

[0042] The RF battery system 1 is typically connected to a power generation unit 211 and a load 212 via a substation 210 and an AC / DC converter 200. The RF battery system 1 charges the power generation unit 211 as a power supply source and discharges the power from the load 212 to which it supplies power. The power generation unit 211 is, for example, a solar power generator, a wind power generator, or other general power plant. The load 212 is, for example, a power grid or a power consumer. The RF battery system 1 is used, for example, for load leveling, instantaneous voltage drop compensation, emergency power supply, or output smoothing of natural energy power generation.

[0043] <RF battery cell> The RF battery cell 10 is separated into a positive electrode cell 12 and a negative electrode cell 13 by a diaphragm 11. The positive electrode cell 12 contains a positive electrode 14. A positive electrode electrolyte is supplied to the positive electrode cell 12. The negative electrode cell 13 contains a negative electrode 15. A negative electrode electrolyte is supplied to the negative electrode cell 13.

[0044] The RF battery cells 10 are typically used in a configuration called a cell stack 5, in which multiple RF battery cells 10 are stacked. The cell stack 5 includes a stack in which a certain cell frame 3, a positive electrode 14, a diaphragm 11, a negative electrode 15, and another cell frame 3 are repeatedly stacked, two end plates 51 that sandwich the stack, and fastening members 52. The fastening members 52 are, for example, long bolts and nuts. The two end plates 51 are fastened together by the fastening members 52. This fastening maintains the stacked state of the stack. The cell stack 5 is typically used in a configuration in which a predetermined number of RF battery cells 10 are treated as sub-stacks (not shown), and multiple sub-stacks are stacked one on top of the other.

[0045] The cell frames 3 include an intermediate cell frame 31 and end cell frames 32. The intermediate cell frame 31 is disposed between adjacent RF battery cells 10 of the stack. The end cell frames 32 are disposed on both ends of the stack.

[0046] The intermediate cell frame 31 includes a frame body 310 and a bipolar plate 311. The frame body 310 is provided on the outer periphery of the bipolar plate 311. The positive electrode 14 and the negative electrode 15 are housed inside the frame body 310 with the bipolar plate 311 sandwiched between them.

[0047] The end cell frame 32 includes a frame body 320 and a conductive member 321. The frame body 320 is provided on the outer periphery of the conductive member 321. The conductive member 321 is a plate-shaped member. Inside the frame body 320, the positive electrode 14 or the negative electrode 15, the current collecting member 7, and the interposing member 8 are housed with the conductive member 321 sandwiched between them. The interposing member 8 is disposed between the conductive member 321 and the current collecting member 7. The positive electrode 14 or the negative electrode 15 is disposed on a first surface of the conductive member 321. The positive electrode 14 or the negative electrode 15 is disposed on a second surface of the conductive member 321, but the interposing member 8 and the current collecting member 7 are disposed on the second surface of the conductive member 321. The interposing member 8 is in contact with the second surface of the conductive member 321. The current collecting member 7 and the interposing member 8 are plate-shaped members. The conductive member 321, the current collecting member 7, and the interposing member 8 will be described later.

[0048] A single RF battery cell 10 is configured by placing a positive electrode 14 and a negative electrode 15 with a diaphragm 11 between the bipolar plates 311 of adjacent intermediate cell frames 31, and between the bipolar plate 311 of the intermediate cell frame 31 and the conductive member 321 of the end cell frame 32. A seal member 315 is placed between the frames 310, 320 to prevent electrolyte from leaking from the RF battery cell 10.

[0049] A supply / discharge plate 6 is arranged on the outside of the end cell frames 32 in the sub-stack and cell stack 5. Outward pipes 24, 25 and return pipes 26, 27 of a circulation mechanism, which will be described later, are connected to the supply / discharge plate 6. Positive electrode electrolyte and negative electrode electrolyte are circulated through the RF battery cells 10 via the supply / discharge plate 6.

[0050] ≪Circulation mechanism≫ The circulation mechanism includes a positive electrode circulation mechanism that circulates the positive electrode electrolyte through the positive electrode cell 12, and a negative electrode circulation mechanism that circulates the negative electrode electrolyte through the negative electrode cell 13. The positive electrode circulation mechanism includes a positive electrode tank 22, an outward piping 24, a return piping 26, and a pump 28. The positive electrode tank 22 stores the positive electrode electrolyte. The outward piping 24 and the return piping 26 connect the positive electrode tank 22 and the positive electrode cell 12. The pump 28 is provided in the outward piping 24 on the supply side. The negative electrode circulation mechanism includes a negative electrode tank 23, an outward piping 25, a return piping 27, and a pump 29. The negative electrode tank 23 stores the negative electrode electrolyte. The outward piping 25 and the return piping 27 connect the negative electrode tank 23 and the negative electrode cell 13. The pump 29 is provided in the outward piping 25 on the supply side.

[0051] The positive electrode electrolyte is supplied from the positive electrode tank 22 through an outward pipe 24 to the positive electrode cell 12, and is returned from the positive electrode cell 12 through a return pipe 26 to the positive electrode tank 22. The negative electrode electrolyte is supplied from the negative electrode tank 23 through an outward pipe 25 to the negative electrode cell 13, and is returned from the negative electrode cell 13 through a return pipe 27 to the negative electrode tank 23. By circulating the positive electrode electrolyte through the positive electrode cell 12 and the negative electrode electrolyte through the negative electrode cell 13, charging and discharging occur in accordance with a valence change reaction of the active material ions in the electrolyte of each electrode.

[0052] The positive electrode electrolyte and the negative electrode electrolyte are solutions containing active material ions. The active material ions are ions that function as active materials. The active material ions are typically metal ions whose valence changes through oxidation-reduction. The active material ions are, for example, ions of elements selected from the group consisting of manganese, vanadium, iron, chromium, titanium, and zinc.

[0053] <Current collector structure for RF battery> Referring to FIGS. 2 to 9, the current collector structure 100 for an RF battery according to an embodiment will be described. FIG. 2 is a simplified schematic diagram of the cell stack 5 shown in FIG. 1. As shown in FIG. 2, the current collector structure 100 for an RF battery includes a conductive member 321, an intervening member 8, and a current collector member 7 that are sequentially stacked on one surface of the positive electrode 14 or the negative electrode 15. One of the features of the current collector structure 100 for an RF battery according to the embodiment lies in the constituent material of the intervening member 8. Hereinafter, each component will be described in detail.

[0054] ≪Conductive member≫ The conductive member 321 has a surface that contacts the positive electrode 14 or the negative electrode 15. In the conductive member 321 located on the left side of the paper surface of FIG. 2, the surface on the right side of the paper surface is in contact with the positive electrode 14. In the conductive member 321 located on the right side of the paper surface of FIG. 2, the surface on the left side of the paper surface is in contact with the negative electrode 15.

[0055] The conductive member 321 is made of a conductive material. The conductive member 321 is preferably corrosion-resistant and flexible. The conductive member 321 may be made of, for example, only a conductive material. The conductive member 321 may also be made of a composite material containing a conductive material and an insulating material. The conductive material constituting the conductive member 321 is preferably mainly composed of carbon. The carbon is, for example, graphite, carbon black, or diamond-like carbon. The carbon contained in the conductive member 321 may be in the form of, for example, powder or fiber. When the conductive material is mainly composed of carbon, it means that the carbon content of the conductive material is greater than 50% by mass. The carbon content of the conductive material is preferably 70% by mass or more, 80% by mass or more, 90% by mass or more, and particularly 100% by mass. The conductive member 321 is generally made of the composite material. A typical example of an insulating material is resin. The resin is, for example, a thermoplastic resin. Examples of thermoplastic resins include polyethylene (PE), polypropylene (PP), polytetrafluoroethylene (PTFE), perfluoroalkoxyalkane (PFA), perfluoroethylenepropene copolymer (FEP), and polyphenylene sulfide (PPS). When the conductive member 321 is made of the above composite material, the proportion of the conductive material in the composite material is, for example, 40% by mass or more and 90% by mass or less. The conductive member 321 in this example is made of the same material as the bipolar plate 311. The conductive member 321 in this example is a conductive plastic containing graphite. The conductive member 321 may be made of a different material from that of the bipolar plate 311.

[0056] <Current collecting material> The current collecting member 7 inputs and outputs electricity between the cell stack 5 and an external device (not shown). The current collecting member 7 is electrically connected to the conductive member 321. The current collecting member 7 is pressed against the conductive member 321 by being fastened by the fastening member 52. For ease of explanation, the electrical leads connected to the current collecting member 7 are omitted from FIG. 2.

[0057] The current collecting member 7 is made of a conductive material. The current collecting member 7 is made of, for example, a metal. The metal is, for example, at least one metal selected from the group consisting of chromium, aluminum, tin, nickel, copper, silver, titanium, gold, platinum, zinc, iron, and lead, or an alloy thereof. The current collecting member 7 is preferably mainly composed of copper or nickel. The current collecting member 7 being mainly composed of copper means that the copper content in the constituent material of the current collecting member 7 is greater than 50 mass%. The copper content in the constituent material of the current collecting member 7 is preferably 70 mass% or more, 80 mass% or more, 90 mass% or more, and particularly 100 mass%. The current collecting member 7 being mainly composed of nickel means that the nickel content in the constituent material of the current collecting member 7 is greater than 50 mass%. The nickel content in the constituent material of the current collecting member 7 is preferably 70 mass% or more, 80 mass% or more, 90 mass% or more, and particularly 100 mass%. The current collecting member 7 is preferably made of pure copper, a copper alloy, pure nickel, or a nickel alloy. When the main component of the current collecting member 7 is copper or nickel, the current collecting member 7 has high conductivity and high strength. The current collecting member 7 in this example is made of pure copper.

[0058] ≪Intervening member≫ Intermediate member 8 is disposed between conductive member 321 and current collecting member 7. Intermediate member 8 is provided mainly to ensure electrical connection between conductive member 321 and current collecting member 7 even when the pressure inside cell stack 5 changes. Intermediate member 8 has the deformability to maintain good electrical connection between conductive member 321 and current collecting member 7. This deformability means that even when the distance between conductive member 321 and current collecting member 7 changes due to pressure changes inside cell stack 5, the intermediate member 8 can maintain contact with conductive member 321, and has elasticity that enables it to deform so as to maintain contact between intermediate member 8 and current collecting member 7.

[0059] The interposing member 8 is a porous body made of a composite material containing a first conductive material and a second conductive material. The interposing member 8 has a skeleton with a three-dimensional mesh structure made of a conductive material. The porous body is, for example, a mesh, a woven fabric, a knitted fabric, a nonwoven fabric, or a porous metal body. The interposing member 8 can also be made of a combination of two or more of the mesh, woven fabric, knitted fabric, nonwoven fabric, and a porous metal body. The interposing member 8 ensures the above-mentioned deformability mainly through the pores of the porous body or the elasticity of the constituent materials.

[0060] One of the features of the current collecting structure 100 for an RF battery according to the embodiment is that the standard electrode potential of the first conductive material and the standard electrode potential of the second conductive material satisfy specific conditions. The standard electrode potential of the first conductive material is closer to the standard electrode potential of the conductive member 321 than to the standard electrode potential of the current collecting member 7. The standard electrode potential of the second conductive material is closer to the standard electrode potential of the current collecting member 7 than to the standard electrode potential of the conductive member 321.

[0061] The first conductive material and the second conductive material are different. Hereinafter, the intermediate value between the standard electrode potential of the conductive member 321 and the standard electrode potential of the current collecting member 7 will be simply referred to as the intermediate value. The standard electrode potential of the first conductive material being closer to the standard electrode potential of the conductive member 321 than the standard electrode potential of the current collecting member 7 means that the potential difference between the standard electrode potential of the first conductive material and the standard electrode potential of the conductive member 321 is smaller than the potential difference between the standard electrode potential of the first conductive material and the standard electrode potential of the current collecting member 7. In other words, the potential difference between the standard electrode potential of the first conductive material and the standard electrode potential of the conductive member 321 is smaller than the potential difference between the intermediate value and the standard electrode potential of the conductive member 321. For example, if the standard electrode potential of the conductive member 321 is smaller than the standard electrode potential of the current collecting member 7, the standard electrode potential of the first conductive material is smaller than the intermediate value.

[0062] The standard electrode potential of the second conductive material being closer to the standard electrode potential of the current collecting member 7 than the standard electrode potential of the conductive member 321 means that the potential difference between the standard electrode potential of the second conductive material and the standard electrode potential of the current collecting member 7 is smaller than the potential difference between the standard electrode potential of the second conductive material and the standard electrode potential of the conductive member 321. In other words, the potential difference between the standard electrode potential of the second conductive material and the standard electrode potential of the current collecting member 7 is smaller than the potential difference between the above-mentioned intermediate value and the standard electrode potential of the current collecting member 7. For example, when the standard electrode potential of the current collecting member 7 is higher than the standard electrode potential of the conductive member 321, the standard electrode potential of the second conductive material is higher than the above-mentioned intermediate value.

[0063] When the standard electrode potentials of the first conductive material and the second conductive material satisfy the above-mentioned specific conditions, the potential difference between the conductive member 321 and the interposed member 8 is small, and the potential difference between the current collecting member 7 and the interposed member 8 is also small. For example, the potential difference between the conductive member 321 and the interposed member 8 is 0.35 V or less, further 0.30 V or less, and particularly 0.20 V or less. The potential difference between the current collecting member 7 and the interposed member 8 is also, for example, 0.35 V or less, further 0.30 V or less, and particularly 0.20 V or less. The potential difference is the potential difference between the standard electrode potential of the conductive member 321 and the interposed member 8, or the potential difference between the standard electrode potential of the current collecting member 7 and the interposed member 8.

[0064] The standard electrode potential here is the potential relative to a standard hydrogen electrode in artificial seawater as defined in JIS Z 0103: 1996. An example of the standard electrode potential in artificial seawater is shown below. Chromium: Approx. -0.91V to Approx. -0.74V Aluminum 1100: Approx. -0.74V to Approx. -0.72V Tin: Approx. -0.58V Nickel: Approx. -0.22V to Approx. -0.17V ·Copper approx.-0.22V ·Silver approx.-0.18V~approx.-0.14V Titanium: Approx. -0.18V to Approx. -0.16V Stainless steel: Approx. -0.17V to Approx. -0.12V ·Gold approx. 0.08V ~ approx. 0.12V ·Platinum Approx. 0.18V~Approx. 0.24V Zinc: Approx. -1.0V Iron: Approx. -0.58V ·Lead approx. -0.55V Carbon (graphite) approx. 0.26V to approx. 0.32V

[0065] The first conductive material is, for example, the same type of conductive material as the constituent material of the conductive member 321. The constituent materials being the same type of conductive material means that the conductive material has the same most abundant component. Generally, the main component of the conductive material that constitutes the conductive member 321 is carbon. Therefore, the main component of the first conductive material is carbon. The first conductive material may be mainly composed of a metal other than carbon as long as it satisfies the above-mentioned specific conditions. In this case, the first conductive material may be selected to be a material that ensures that the potential difference between the conductive member 321 and the interposed member 8 is 0.35 V or less.

[0066] The second conductive material is, for example, the same type of material as the conductive material in the constituent material of the current collecting member 7. As described above, the constituent material of the current collecting member 7 is a metal. Therefore, the constituent metal of the second conductive material and the constituent metal of the current collecting member 7 are the same type. The term "same type of metal" means that the majority component in the composition is the same metal, and includes metals with different compositional components. For example, a pure metal and an alloy containing that pure metal as the main component are treated as the same metal. Furthermore, even if alloys contain different additive elements, they are treated as the same metal if the main component is the same metal element.

[0067] When the current collecting member 7 is primarily composed of copper, the second conductive material is primarily composed of, for example, copper or nickel. When the current collecting member 7 is primarily composed of copper, the second conductive material is preferably primarily composed of copper. When the current collecting member 7 is primarily composed of nickel, the second conductive material is primarily composed of, for example, copper or nickel. When the current collecting member 7 is primarily composed of nickel, the second conductive material is preferably primarily composed of nickel. When the second conductive material and the current collecting member 7 are made of the same material, the potential difference between the current collecting member 7 and the interposed member 8 is likely to be small. The constituent metal of the second conductive material may be different from the constituent metal of the current collecting member 7 as long as the above-mentioned specific conditions are met. In this case, the second conductive material may be selected so that the potential difference between the current collecting member 7 and the interposed member 8 is 0.35 V or less.

[0068] The interposition member 8 may have a form including wires or a form including particles, for example. Three specific forms will be described below.

[0069] [Form 1] As shown in FIG. 3, the intervening member 8 of Form 1 is a mixture of multiple wires including first wires 81 and second wires 82. In the intervening member 8 of Form 1, an assembly 80 of the mixed multiple wires forms the skeleton of a porous body. The first wires 81 are made of a first conductive material. The second wires 82 are made of a second conductive material. The intervening member 8 of Form 1 is composed of a woven fabric in which the first wires 81 and the second wires 82 are arranged alternately. In FIG. 3, for ease of understanding, the first wires 81 are indicated by solid lines and the second wires 82 are indicated by two-dot chain lines. This is the same as in the other figures.

[0070] The conductive member 321 is in contact with both the first wire 81 and the second wire 82. The first conductive material constituting the first wire 81 has a standard electrode potential closer to that of the conductive member 321 than that of the second conductive material constituting the second wire 82. Therefore, the potential difference between the conductive member 321 and the first wire 81 is smaller than the potential difference between the conductive member 321 and the second wire 82. By having the conductive member 321 in contact with both the first wire 81 and the second wire 82, the number of areas prone to corrosion is reduced compared to when the conductive member 321 is in contact with only the second wire 82, and corrosion is suppressed.

[0071] The current collecting member 7 is in contact with both the first wire 81 and the second wire 82. The second conductive material constituting the second wire 82 has a standard electrode potential closer to that of the current collecting member 7 than the first conductive material constituting the first wire 81. Therefore, by having the current collecting member 7 in contact with both the first wire 81 and the second wire 82, the number of areas prone to corrosion is reduced compared to when the current collecting member 7 is in contact with only the first wire 81, and corrosion is suppressed.

[0072] In the interposing member 8 of the first embodiment, as shown in FIG. 4, a void 800 is formed by the first wire 81 and the second wire 82. FIG. 4 is a schematic cross-sectional view showing an enlarged view of the circle surrounded by the dashed line IV in FIG. 3. The void 800 in this example is provided with a filling portion 88. The filling portion 88 is provided to prevent moisture from penetrating into the interposing member 8 even if moisture penetrates between the conductive member 321 and the current collecting member 7. The filling portion 88 shown in FIG. 4 is made of a polymer material 88a. The polymer material 88a is, for example, a resin, rubber, or gel. The polymer material 88a in this example is a resin. The resin is, for example, the same as the resin constituting the conductive member 321. The filling portion 88 shown in FIG. 4 is insulating.

[0073] As shown in FIG. 5, the filling portion 88 may be made of a composite material in which a plurality of conductive fillers 88b are dispersed in a polymer material 88a. Similar to FIG. 4, FIG. 5 is a schematic cross-sectional view enlarging the area within the circle surrounded by the dashed line IV in FIG. 3. In FIG. 5, the conductive fillers 88b are not hatched. The constituent metal of the conductive filler 88b is the same as the constituent metal of the current collecting member 7, for example. The shape of the conductive filler 88b is, for example, granular, flake-like, or short fiber-like. In this example, the conductive filler 88b is mainly granular. The dispersed conductive fillers 88b make the filling portion 88 shown in FIG. 5 conductive.

[0074] The filling portion 88 is formed by spraying, for example, a liquid polymer material 88a or a mixed liquid in which a plurality of conductive fillers 88b are dispersed in the liquid polymer material 88a onto the assembly 80. By spraying, the liquid polymer material 88a enters the voids 800. Thereafter, the liquid polymer material 88a is solidified, and the filling portion 88 is formed in the voids 800. In other words, the voids 800 filled with the filling portion 88 exist.

[0075] [Form 2] As shown in FIG. 6 , the interposing member 8 of Form 2 includes an aggregate 80 and a plurality of first particles 85. The aggregate 80 is composed of a plurality of second wires 82. In the interposing member 8 of Form 2, the aggregate 80 of a plurality of second wires 82 forms the skeleton of a porous body. The first particles 85 are dispersed and arranged on the surface of the aggregate 80 that contacts the conductive member 321. The first particles 85 are, for example, embedded in pores between the plurality of second wires 82 that constitute the aggregate 80 and adhere to the aggregate 80. The first particles 85 may be attached to the aggregate 80 by a binder (not shown). The binder may be made of, for example, the same material as the resin that constitutes the conductive member 321. The binder is preferably made of PE or PP. It is preferable that the surface of the aggregate 80 that contacts the current collecting member 7 is empty and is composed of the second wires 82. The first particles 85 are made of a first conductive material. The second wires 82 are made of a second conductive material.

[0076] The conductive member 321 mainly contacts the first particles 85. The conductive member 321 may also contact the second wire 82. The first conductive material constituting the first particles 85 has a standard electrode potential closer to the conductive member 321 than the second conductive material constituting the second wire 82. Therefore, by the conductive member 321 mainly contacting the first particles 85 in a patchy manner, the number of areas prone to corrosion is reduced compared to when the conductive member 321 contacts only the second wire 82, and corrosion is suppressed.

[0077] The current collecting member 7 mainly contacts the second wire 82. In this example, the current collecting member 7 contacts only the second wire 82. Because the second wire 82 is made of the second conductive material, the potential difference between the current collecting member 7 and the interposed member 8 is small. If the second conductive material is the same as the constituent metal of the current collecting member 7, the potential difference between the current collecting member 7 and the interposed member 8 is substantially zero.

[0078] In the intervening member 8 of form 2, voids are formed between the plurality of second wires 82 that make up the assembly 80. In the intervening member 8 of form 2 as well, as in the intervening member 8 of form 1, the voids may be provided with filling portions 88 as shown in Figs. 4 and 5 .

[0079] [Form 3] As shown in FIG. 7 , the interposing member 8 of Form 3 includes an aggregate 80 and a plurality of second particles 86. The aggregate 80 is composed of a plurality of first wires 81. In the interposing member 8 of Form 3, the aggregate 80 of a plurality of first wires 81 forms the skeleton of a porous body. The second particles 86 are dispersed and arranged on the surface of the aggregate 80 that contacts the current collecting member 7. The second particles 86 are, for example, embedded in pores between the plurality of first wires 81 that constitute the aggregate 80 and adhere to the aggregate 80. The second particles 86 may be attached to the aggregate 80 by a binder (not shown). The binder is the same as the binder of Form 2. It is preferable that nothing is arranged on the surface of the aggregate 80 that contacts the conductive member 321, and that the surface is composed of the first wires 81. The second particles 86 are made of a second conductive material. The first wires 81 are made of a first conductive material.

[0080] The conductive member 321 mainly contacts the first wire 81. In this example, the conductive member 321 contacts only the first wire 81. Because the first wire 81 is made of the first conductive material, the potential difference between the conductive member 321 and the interposed member 8 is small. As described above, the conductive member 321 generally contains carbon as a conductive material. When the first conductive material is made of carbon, the potential difference between the conductive member 321 and the interposed member 8 is substantially zero.

[0081] The current collecting member 7 is mainly in contact with the second particles 86. The current collecting member 7 may also be in contact with the first wire 81. The second conductive material constituting the second particles 86 has a standard electrode potential closer to the current collecting member 7 than the first conductive material constituting the first wire 81. Therefore, by the current collecting member 7 being in patchy contact mainly with the second particles 86, the number of areas susceptible to corrosion is reduced compared to when the current collecting member 7 is in contact only with the first wire 81, and corrosion is suppressed.

[0082] In the intervening member 8 of form 3, voids are formed between the plurality of first wires 81 that make up the assembly 80. In the intervening member 8 of form 3 as well, as in the intervening member 8 of form 1, the voids may be provided with filling portions 88 as shown in Figs. 4 and 5 .

[0083] In the interposition member 8 of the above-described first to third embodiments, at least a portion of the plurality of wires constituting the assembly 80 may be a twisted wire in which a plurality of elemental wires 83 are twisted together, as shown in FIG. 8 . In the interposition member 8 of the first embodiment, the plurality of wires are a plurality of first wires 81 and a plurality of second wires 82. In the interposition member 8 of the second embodiment, the plurality of wires are a plurality of second wires 82. In the interposition member 8 of the third embodiment, the plurality of wires are a plurality of first wires 81. In the first wires 81, each elemental wire 83 is made of a first conductive material. In the second wires 82, each elemental wire 83 is made of a second conductive material. The number of elemental wires 83 in each wire, the twist pitch, etc. can be selected as appropriate.

[0084] In the interposition member 8 of the above-described first to third embodiments, at least some of the plurality of wires constituting the assembly 80 may have a plating layer 84b on the surface of the core portion 84a, as shown in FIG. 9 . In the interposition member 8 of the first embodiment, the plurality of wires are a plurality of first wires 81 and a plurality of second wires 82. In the interposition member 8 of the second embodiment, the plurality of wires are a plurality of second wires 82. In the interposition member 8 of the third embodiment, the plurality of wires are a plurality of first wires 81. In the first wire 81, the plating layer 84b is made of the first conductive material. In the second wire 82, the plating layer 84b is made of the second conductive material. For example, in the second wire 82, if the core 84a is mainly composed of copper, the plating layer 84b is mainly composed of nickel. In the second wire 82, if the core 84a is mainly composed of nickel, the plating layer 84b is mainly composed of copper. The thickness of the plating layer 84b can be selected as appropriate.

[0085] In the interposition member 8 of the above-described first to third embodiments, at least some of the plurality of wires constituting the assembly 80 may be a stranded wire in which element wires having a core portion without a plating layer are twisted together. At least some of the plurality of wires may be a stranded wire in which element wires having a plating layer 84b shown in Fig. 9 are twisted together. At least some of the plurality of wires may be a concentric strand in which element wires having a core portion without a plating layer and element wires having the plating layer 84b shown in Fig. 9 are twisted together.

[0086] In the RF battery current collecting structure 100 of the embodiment, the first conductive material and the second conductive material constituting the interposed member 8 each have a specific potential, thereby reducing the potential difference between the conductive member 321 and the interposed member 8 and reducing the potential difference between the current collecting member 7 and the interposed member 8. Specifically, the potential difference between the conductive member 321 and the interposed member 8 and the potential difference between the current collecting member 7 and the interposed member 8 are each 0.35 V or less. Because the potential differences are small, even if moisture penetrates between the conductive member 321 and the interposed member 8 and between the current collecting member 7 and the interposed member 8, corrosion is unlikely to occur.

[0087] When the intervening member 8 is configured as an assembly 80 of a mixture of multiple wires including first wires 81 and second wires 82, the alternating arrangement of the first wires 81 and the second wires 82 tends to reduce the potential difference. In particular, when the intervening member 8 includes an assembly 80 made of second wires 82 and first particles 85, the current collecting member 7 can be in contact with only the second wires 82, and the potential difference between the current collecting member 7 and the intervening member 8 can be substantially zero. Similarly, when the intervening member 8 includes an assembly 80 made of first wires 81 and second particles 86, the conductive member 321 can be in contact with only the first wires 81, and the potential difference between the conductive member 321 and the intervening member 8 can be substantially zero.

[0088] By providing the filling portions 88 in the pores 800 of the porous body constituting the interposed member 8, even if moisture penetrates between the conductive member 321 and the current collecting member 7, the moisture can be prevented from penetrating into the interposed member 8. When a plurality of conductive fillers 88b are dispersed in the filling portions 88, the conductivity provided by the filling portions 88 can also be ensured.

[0089] The RF battery current collecting structure 100 of the embodiment uses known conductive members 321 and current collecting members 7. Therefore, the RF battery current collecting structure 100 of the embodiment can suppress corrosion between the conductive member 321 and the current collecting member 7 with a simple configuration.

[0090] The RF battery cell 10 and RF battery system 1 of the embodiment, which include the RF battery current collecting structure 100 of the embodiment, can suppress corrosion between the conductive member 321 and the current collecting member 7, and can suppress an increase in contact resistance between the conductive member 321 and the current collecting member 7. Therefore, the RF battery cell 10 and RF battery system 1 of the embodiment can stably maintain battery performance over a long period of time. [Explanation of symbols]

[0091] 1 Redox flow battery system (RF battery system) 10 Redox flow battery cells (RF battery cells) 100 Current collecting structure for redox flow batteries (current collecting structure for RF batteries) 11 Diaphragm 12 positive electrode cell, 13 negative electrode cell 14 positive electrode, 15 negative electrode 22 positive electrode tank, 23 negative electrode tank 24, 25 Outward piping, 26, 27 Return piping 28, 29 Pump 3 Cell Frame 31 intermediate cell frame, 310 frame body, 311 bipolar plate, 315 sealing member 32 end cell frame, 320 frame body, 321 conductive member 5 cell stack, 51 end plate, 52 fastening member 6 Supply / discharge plate 7 Current collecting member 8 Intervening member 80 aggregates, 800 pores 81 first wire rod, 82 second wire rod, 83 wire, 84a core, 84b plating layer 85 first particle, 86 second particle 88 filling portion, 88a polymer material, 88b conductive filler 200 AC / DC converter, 210 substation equipment, 211 power generation unit, 212 load

Claims

1. A current collecting structure for a redox flow battery, comprising a conductive member, an interposing member, and a current collecting member stacked in this order on one surface of a positive electrode or a negative electrode, The intervening member is a porous body made of a composite material including a first conductive material and a second conductive material, a plurality of wires including a wire made of the first conductive material and a wire made of the second conductive material are mixed together; a standard electrode potential of the first conductive material is closer to a standard electrode potential of the conductive member than to a standard electrode potential of the current collecting member; a standard electrode potential of the second conductive material is closer to a standard electrode potential of the current collecting member than to a standard electrode potential of the conductive member; Current collecting structure for redox flow batteries.

2. A current collecting structure for a redox flow battery, comprising a conductive member, an interposing member, and a current collecting member stacked in this order on one surface of a positive electrode or a negative electrode, The intervening member is a porous body made of a composite material including a first conductive material and a second conductive material, a plurality of particles of the first conductive material; an assembly of a plurality of wires made of the second conductive material; the plurality of particles are dispersed and arranged on a surface of the assembly that comes into contact with the conductive member, a standard electrode potential of the first conductive material is closer to a standard electrode potential of the conductive member than to a standard electrode potential of the current collecting member; a standard electrode potential of the second conductive material is closer to a standard electrode potential of the current collecting member than to a standard electrode potential of the conductive member; Current collecting structure for redox flow batteries.

3. A current collecting structure for a redox flow battery, comprising a conductive member, an interposing member, and a current collecting member stacked in this order on one surface of a positive electrode or a negative electrode, The intervening member is a porous body made of a composite material including a first conductive material and a second conductive material, a plurality of particles of the second conductive material; an assembly of a plurality of wires made of the first conductive material; the plurality of particles are dispersed and arranged on a surface of the assembly that comes into contact with the current collecting member, a standard electrode potential of the first conductive material is closer to a standard electrode potential of the conductive member than to a standard electrode potential of the current collecting member; a standard electrode potential of the second conductive material is closer to a standard electrode potential of the current collecting member than to a standard electrode potential of the conductive member; Current collecting structure for redox flow batteries.

4. 4. The current collecting structure for a redox flow battery according to claim 1, wherein at least a portion of the plurality of wires is a stranded wire formed by twisting together a plurality of wires.

5. The current collecting structure for a redox flow battery according to claim 1 , wherein at least some of the plurality of wires have a plating layer on a surface of a core portion.

6. a main component of one of the core portion and the plating layer is copper; The current collecting structure for a redox flow battery according to claim 5 , wherein the main component of the other of the core portion and the plating layer is nickel.

7. A current collecting structure for a redox flow battery, comprising a conductive member, an interposing member, and a current collecting member stacked in this order on one surface of a positive electrode or a negative electrode, The intervening member is a porous body made of a composite material including a first conductive material and a second conductive material, an insulating filling portion provided in the pores of the porous body; the filling portion is made of a polymer material, a standard electrode potential of the first conductive material is closer to a standard electrode potential of the conductive member than to a standard electrode potential of the current collecting member; a standard electrode potential of the second conductive material is closer to a standard electrode potential of the current collecting member than to a standard electrode potential of the conductive member; Current collecting structure for redox flow batteries.

8. A current collecting structure for a redox flow battery, comprising a conductive member, an interposing member, and a current collecting member stacked in this order on one surface of a positive electrode or a negative electrode, The intervening member is a porous body made of a composite material including a first conductive material and a second conductive material, a conductive filling portion provided in the pores of the porous body; the filling portion is made of a composite material in which a plurality of conductive fillers are dispersed in a polymer material, a standard electrode potential of the first conductive material is closer to a standard electrode potential of the conductive member than to a standard electrode potential of the current collecting member; a standard electrode potential of the second conductive material is closer to a standard electrode potential of the current collecting member than to a standard electrode potential of the conductive member; Current collecting structure for redox flow batteries.

9. a main component of the conductive material constituting the conductive member is carbon; The current collecting structure for a redox flow battery according to claim 1 , wherein the current collecting member is mainly composed of copper or nickel.

10. the first conductive material is mainly composed of carbon; 10. The current collecting structure for a redox flow battery according to claim 9, wherein a main component of the second conductive material is copper or nickel.

11. A current collecting structure for a redox flow battery according to any one of claims 1 to 10, Redox flow battery cell.

12. A redox flow battery cell according to claim 11, Redox flow battery system.

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