TW202002379A - Bipolar plate, cell frame, cell stack, and redox flow battery - Google Patents

Abstract

A bipolar plate having an electrode of a redox flow battery positioned thereon and comprising: a facing surface that faces said electrode; and at least one groove that forms, in the facing surface, a flow path through which an electrolytic solution flows, wherein when the bipolar plate is in planar view, at least one of the grooves has a curved section.

Description

Bipolar plate, unit frame, unit stack, and redox flow battery

The invention relates to a bipolar plate, a unit frame, a unit stack, and a redox flow battery.

As one of large-capacity storage batteries, a redox flow battery (hereinafter, sometimes referred to as "RF (Radio Frequency) battery") is known (for example, refer to Patent Documents 1 and 2). Generally, in an RF battery, a unit stack formed by stacking a plurality of unit frames, a positive electrode, a separator, and a negative electrode is used. The unit frame includes a bipolar plate disposed between the positive electrode and the negative electrode, and a frame body provided on the outer periphery of the bipolar plate. The cell stack is formed by arranging positive and negative electrodes between the bipolar plates of adjacent cell frames with a diaphragm therebetween to form one cell. The RF battery uses a pump to circulate the electrolyte in the cell with the built-in electrodes to charge and discharge.

In Patent Documents 1 and 2, it is described that a plurality of grooves through which electrolyte flows are formed on the electrode side surface of the bipolar plate to constitute a flow path. [Prior Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open No. 2015-122230 [Patent Document 2] Japanese Patent Laid-Open No. 2015-210849

The bipolar plate system of the present invention An electrode for arranging a redox flow battery, having an opposing surface facing the electrode, and having at least one groove forming a flow path for the electrolyte to circulate on the opposing surface, and When looking down on the bipolar plate, at least one of the grooves has a curved portion.

The unit frame of the present invention The bipolar plate of the present invention and the frame provided on the outer periphery of the bipolar plate are provided.

The unit stack system of the present invention The unit frame of the present invention described above is provided.

The redox flow battery system of the present invention The unit stack of the present invention described above is provided.

[Problems to be Solved by the Invention] Further improvement in battery performance of redox flow batteries is desired, and from the viewpoint of improving battery performance, it is required to reduce the internal resistance (cell resistance) of the battery. As a factor of the internal resistance, the flow state of the electrolyte, for example, the flow resistance of the electrolyte, the reaction resistance in the electrode, etc. may be mentioned.

The electrode of the redox flow battery functions as a reaction field that promotes the battery reaction of the active material (metal ions) contained in the supplied electrolyte. For the electrode, a porous material such as carbon felt containing carbon fiber is generally used, and the electrolyte flows into the electrode. When the electrode side of the bipolar plate has a flow path with a groove for electrolyte circulation, the electrolyte flow resistance can be reduced, thereby reducing the pressure loss due to the electrolyte flow resistance. In addition, by using a bipolar plate having a flow path with a groove, the flow of the electrolyte penetrating into the electrode can be controlled to prevent the distribution of the electrolyte in the electrode from becoming uneven. By suppressing the uneven distribution of the electrolyte penetrating into the electrode, the reactivity of the electrode and the electrolyte can be improved, and the reaction resistance in the electrode can be reduced.

However, it may not be possible to say that the internal resistance has been sufficiently studied before considering the flow state of the electrolyte in the electrode. The previous bipolar plate is mainly composed of straight grooves, so the layout of the grooves has a low degree of freedom, it is difficult to fully improve the uniformity of the electrolyte distribution in the electrode, etc., and improve the reactivity of the electrode and the electrolyte Room.

Therefore, one of the objects of the present invention is to provide a bipolar plate that can reduce the flow resistance of the electrolyte and improve the reactivity of the electrode and the electrolyte. Moreover, one of the objects of the present invention is to provide a cell frame and a cell stack that can improve battery performance. Furthermore, one of the objects of the present invention is to provide a redox flow battery with excellent battery performance.

[Effect of the invention] According to the present invention, it is possible to provide a bipolar plate capable of reducing the flow resistance of the electrolyte and improving the reactivity of the electrode and the electrolyte. Furthermore, according to the present invention, it is possible to provide a cell frame and a cell stack capable of improving battery performance. Furthermore, according to the present invention, a redox flow battery excellent in battery performance can be provided.

[Description of the embodiment of the invention of the present case] First, the content of the embodiment of the present invention will be listed and described.

(1) The bipolar plate system of the embodiment An electrode for arranging a redox flow battery, having an opposing surface facing the electrode, and having at least one groove forming a flow path for the electrolyte to circulate on the opposing surface, and When looking down on the bipolar plate, at least one of the grooves has a curved portion.

According to the above-mentioned bipolar plate, by forming an electrolyte flow path on the opposite surface to the electrode, the flow resistance of the electrolyte can be reduced, and the distribution of the electrolyte penetrating into the electrode can be controlled. Since at least one of the grooves constituting the flow path has a curved portion, the degree of freedom of layout is improved compared to a linear groove. Therefore, the grooves can be efficiently arranged so that the distribution of the electrolyte in the electrode becomes uniform. Thereby, the uniformity of the distribution of the electrolyte in the electrode can be sufficiently improved, and the reactivity of the electrode and the electrolyte can be improved. Therefore, the above-mentioned bipolar plate can reduce the flow resistance of the electrolyte, and can improve the reactivity of the electrode and the electrolyte. Therefore, when the above bipolar plate is used in a redox flow battery, the pressure loss due to the flow resistance of the electrolyte can be reduced, and the reaction resistance in the electrode can be reduced. Therefore, the internal resistance of the battery can be reduced ( Cell resistance).

The "curved portion" of a groove refers to a portion that is curved in the length direction of the groove. The representative part of the curve is a non-periodic curve.

(2) As one form of the above-mentioned bipolar plate, The curvature radius of the above-mentioned curved portion is 0.1 mm or more.

When the radius of curvature of the curved portion is 0.1 mm or more, it is easy to form a groove with a curved portion. The upper limit of the radius of curvature of the curved portion is not particularly limited, and is, for example, 100 mm or less.

(3) As one form of the above-mentioned bipolar plate, It can be mentioned that the opening width of the above-mentioned groove becomes smaller toward the front end side.

As the opening width of the tank becomes smaller toward the front end side, the pressure of the electrolyte becomes higher as it approaches the front end side, so that the electrolyte easily penetrates from the tank into the electrode.

(4) As one form of the above-mentioned bipolar plate, For example, when the contact area of the bipolar plate in contact with the electrode is A, and the planar opening area of the groove is B, A/(A+B) exceeds 0.5 and does not reach 0.95.

The ratio of the contact area of the electrode (A) to the area of the opposite surface of the bipolar plate (A+B) [A/(A+B)] exceeds 0.5 to ensure contact between the electrode and the bipolar plate Area to reduce the contact resistance between the electrode and the bipolar plate. This can reduce the internal resistance (cell resistance) of the battery. Also, from the viewpoint of ensuring the formation area of the groove in the opposing surface of the bipolar plate (the flow path area of the electrolyte), it is preferable that the ratio of the contact area of the electrode [A/(A+B)] is not reached 0.95, thereby effectively reducing the flow resistance of the electrolyte.

The "planar opening area" of the groove refers to the opening area of the groove in the facing surface when looking down on the bipolar plate.

(5) As one form of the above-mentioned bipolar plate, It may be mentioned that the width of the opening side of the groove is more than the width of the bottom side in the cross section of the groove orthogonal to the flow direction of the electrolyte.

In the cross section of the groove, the width of the opening side of the groove is more than the width of the bottom side, and it is easier to form the groove than the case where the width of the bottom side is wider than the width of the opening side.

(6) As one form of the bipolar plate as described in (5) above, A cross-sectional shape of the above-mentioned groove may be tapered from the opening side toward the bottom side.

The cross section of the groove is formed into a tapered shape from the opening side toward the bottom side, so that the electrolyte easily penetrates into the electrode from the groove.

(7) As one form of the above-mentioned bipolar plate, It can be mentioned that the above-mentioned groove system is formed in a dendritic shape, and includes a trunk groove portion, and at least one branch groove portion branched from the trunk groove portion, and At least one of the branch groove portions intersects the main groove portion non-orthogonally.

By forming the trough into a dendritic shape, it is easy for the electrolyte to penetrate and diffuse from the trough over a large area in the electrode, so that the distribution of the electrolyte in the electrode can be more uniform. Therefore, the reactivity of the electrode and the electrolyte can be further improved. In addition, since the branch groove portion branched from the main trunk groove portion crosses non-orthogonally with respect to the main groove portion, the flow resistance of the electrolyte can be reduced compared to the case where the branch groove portion is orthogonal to the main groove portion.

(8) As one form of the bipolar plate as described in (7) above, It can be mentioned that at least one of the branch groove portions has the curved portion.

By having a curved portion in the branch groove portion, the groove can be efficiently arranged.

(9) As one form of the bipolar plate as described in (7) or (8) above, At least one of the branch groove portions may have a branch groove portion further branched from the branch groove portion.

By having the branch groove portion further branching from the branch groove portion, it is easy for the electrolytic solution to efficiently penetrate and diffuse into the electrode.

(10) As one form of the bipolar plate as described in (9) above, When N (N: natural number) is the branching frequency of the branch groove portion, N is 3 or less.

By repeating the branching of the autonomous trunk part, the groove width (opening width) of the branch groove part after branching is reduced and narrowed. By limiting the number of branches (N) of the branch groove part to 3 or less, it is possible to avoid excessive narrowing of the groove width of the branch groove part due to branching.

"Branch frequency" refers to the number of times that the branch of the main trunk is counted from the branch of the trunk. When there is a branch trough part (primary branch trough) of an autonomous trunk trough, set the number of branches to 1, when there is a branch trough part (secondary branch trough) branching further from the branch trough part, The branch count is 2. In addition, when there is a branch groove portion (third-order branch groove) that branches further from the secondary branch groove, the number of branches is counted as 3. The above "N" is a natural number (1, 2, 3, ...).

(11) As one form of the bipolar plate as described in (9) or (10) above, The opening width of the branch groove portion after branching is smaller than the opening width of the branch groove portion before branching.

The opening width of the branch groove portion after branching gradually decreases each time the branch passes, and the contact area between the electrode and the bipolar plate increases, thereby reducing the contact resistance between the electrode and the bipolar plate.

(12) As one form of the above-mentioned bipolar plate, The above-mentioned flow path can be listed as follows: The inlet and outlet of the above electrolyte; An introduction path that introduces the electrolyte from the inlet; and A discharge path, which is independent of the introduction path and discharges the electrolyte to the discharge port; The introduction path and the discharge path each include at least one of the grooves, and At least one of the introduction path and the discharge path includes a rectifying portion connected to the introduction port or the discharge port and formed along the edge of the bipolar plate.

The flow path is provided with an introduction path and a discharge path, and the electrolytic solution flows so as to flow between the introduction path and the discharge path. At this time, the electrolytic solution permeates and diffuses into the electrode, so that the electrolytic solution can be uniformly distributed throughout the electrode. In this way, the distribution of the electrolyte in the electrode can be more effectively uniformed, so that the reactivity of the electrode and the electrolyte can be further improved. In addition, by providing a rectifying section, the electrolyte can be efficiently introduced or discharged from the introduction port or the discharge port with respect to at least one of the introduction path and the discharge path.

(13) As one form of the bipolar plate as described in (12) above, It can be mentioned that the effective electrode area facing the bipolar plate and the electrode is rectangular, and the introduction port and the discharge port are provided at diagonal positions of the effective electrode area, and The angle formed by the rectifying portion and the diagonal of the effective electrode region is 40° or more and 50° or less.

By forming the angle formed by the rectifier and the diagonal of the effective electrode region to be 40° or more and 50° or less, the pressure loss in the rectifier can be reduced.

(14) As one form of the bipolar plate as described in (12) or (13) above, In the above bipolar plate, when the inlet side is the lower side and the outlet side is the upper side, The above flow path is asymmetrical.

By asymmetry of the flow path between the introduction side and the discharge side, the flow of the electrolyte on the discharge side where the pressure of the electrolyte is reduced can be improved.

(15) As one form of the bipolar plate as described in any one of (12) to (14) above, Examples include opposing comb-tooth regions in which grooves having the introduction path and grooves in the discharge path are alternately arranged to face each other.

Since the flow path has opposed comb-tooth areas, the amount of electrolyte flowing in such a way as to flow between the introduction path and the discharge path increases, and the electrolyte penetration and diffusion into the electrode increases. Thereby, the reaction efficiency of the electrode and the electrolyte can be improved.

(16) As one form of the above-mentioned bipolar plate, It can be mentioned that at least a part of the groove has a wide portion with an opening width of 2 mm or more, and a convex portion protruding from the bottom is formed in the wide portion.

By providing the convex portion in the wide portion of the groove, it is possible to suppress the electrode from being buried in the groove.

(17) The unit frame system of the embodiment A bipolar plate as described in any one of (1) to (16) above, and a frame provided on the outer periphery of the bipolar plate.

The above-mentioned unit frame can reduce the flow resistance of the electrolyte and improve the reactivity of the electrode and the electrolyte by including the bipolar plate of the above-mentioned embodiment. Therefore, the pressure loss due to the flow resistance of the electrolyte can be reduced, and Can reduce the reaction resistance in the electrode. Therefore, when the above cell frame is used in a redox flow battery, the internal resistance (cell resistance) of the battery can be reduced, and the battery performance can be improved.

(18) The unit stack system of the embodiment The unit frame as described in (17) above is provided.

The cell stack provided with the cell frame of the above-mentioned embodiment can reduce the pressure loss due to the flow resistance of the electrolyte, and can also reduce the reaction resistance in the electrode. Therefore, when the above cell stack is used in a redox flow battery, the internal resistance (cell resistance) of the battery can be reduced, and the battery performance can be improved.

(19) Redox flow battery system of the embodiment Equipped with the unit stack as described above (18).

The above-mentioned redox flow battery can reduce the pressure loss due to the flow resistance of the electrolyte and reduce the reaction resistance in the electrode by including the cell stack of the above embodiment, and therefore, the internal resistance (cell resistance) of the battery can be reduced ). Therefore, the above-mentioned redox flow battery has excellent battery performance.

[Details of the embodiment of the invention of the present case] Hereinafter, specific examples of the bipolar plate, cell frame and cell stack, and redox flow battery (RF battery) for the redox flow battery according to the embodiment of the present invention will be described with reference to the drawings. The same symbols in the figures indicate the same or corresponding parts. Furthermore, the invention in this case is not limited to these examples, but is expressed by the scope of patent application, and is intended to include all changes within the meaning and scope equivalent to the scope of patent application.

FIG. 4 is a schematic plan view of the unit frame 3 provided with the bipolar plate 31 of the embodiment as viewed from one side of the bipolar plate 31. One of the characteristics of the bipolar plate 31 of the embodiment is that, as shown in FIG. 4, at least one groove 5 constituting a flow path 4 for the circulation of the electrolyte is provided on the opposite surface to the electrode 14, and the In the case of the pole plate 31, at least one of the grooves 5 has a curved portion.

Hereinafter, the outline of the unit 10 (unit stack 2) and the bipolar plate 31 (unit frame 3) provided in the RF battery 1 and the RF battery 1 of the embodiment will be described with reference to FIGS. 1 to 4 first. Next, referring mainly to FIGS. 4 to 6, the flow path 4 and the groove 5 included in the bipolar plate 31 of the embodiment will be described in detail.

"RF Battery" First, referring to FIGS. 1 to 3, an example of the RF battery 1 and the unit 10 (cell stack 2) of the embodiment will be described. The RF battery 1 shown in FIGS. 1 and 2 uses an electrolyte containing metal ions whose valence changes by oxidation and reduction as an active material for the positive electrolyte and the negative electrolyte, and utilizes the oxidation of the ions contained in the positive electrolyte A battery that is charged and discharged by the difference between the reduction potential and the oxidation-reduction potential of the ions contained in the negative electrode electrolyte. Here, as an example of the RF battery 1, a vanadium-based RF battery using a vanadium electrolyte solution containing V ions for the positive electrode electrolyte and the negative electrode electrolyte is shown. The solid arrows in the cell 10 in FIG. 1 indicate the charging reaction, and the dotted arrows indicate the discharging reaction. The RF battery 1 is connected to the power system P via an AC/DC converter C, and is used for, for example, load leveling applications, transient low compensation or emergency power supplies, and output smoothing applications of natural energy power generation such as photovoltaic power generation or wind power generation .

The RF battery 1 includes a cell 10 for charging and discharging, tanks 106 and 107 for storing electrolyte, and circulation flow paths 100P and 100N for circulating the electrolyte between the tanks 106 and 107 and the cell 10.

"unit" As shown in FIG. 1, the cell 10 has a positive electrode 14, a negative electrode 15, and a separator 11 interposed between the two electrodes 14 and 15. The structure of the unit 10 is separated into a positive electrode unit 12 and a negative electrode unit 13 via a separator 11, and a positive electrode 14 is built in the positive unit 12 and a negative electrode 15 is built in the negative unit 13.

Each of the positive electrode 14 and the negative electrode 15 is formed of a carbon fiber aggregate containing carbon fibers. The electrode of the carbon fiber assembly is porous and has voids in the electrode. Therefore, the electrolyte flows into the electrode to allow the electrolyte to penetrate and diffuse. Examples of the carbon fiber aggregate include carbon felt, carbon cloth, and carbon paper. Examples of carbon fibers include PAN-based carbon fibers using polyacrylonitrile (PAN) fibers as raw materials, pitch-based carbon fibers using pitch fibers as raw materials, and rayon-based carbon fibers using rayon fibers as raw materials. The diaphragm 11 is formed of, for example, an ion exchange membrane that transmits hydrogen ions.

In the unit 10 (positive electrode unit 12 and negative electrode unit 13), the electrolytic solution (positive electrolyte and negative electrode electrolyte) circulates through the circulation flow paths 100P and 100N. The positive electrode unit 12 is connected to a positive electrode electrolyte tank 106 storing positive electrode electrolyte via a positive electrode circulation channel 100P. Similarly, the negative electrode unit 13 is connected to the negative electrode electrolyte tank 107 which stores the negative electrode electrolyte via the negative electrode circulation channel 100N. Each circulation flow path 100P, 100N has outgoing piping 108, 109 which sends electrolyte from each tank 106, 107 to the unit 10, and return piping 110, 111 which returns the electrolyte from the unit 10 to each tank 106, 107. Each of the outgoing piping 108 and 109 is provided with pumps 112 and 113 that pressurize and transport the electrolyte stored in the tanks 106 and 107. The pumps 112 and 113 circulate the electrolyte in the unit 10.

"Unit Stack" The unit 10 may be composed of a single unit including one unit 10, or may be composed of multiple units including a plurality of units 10. The unit 10 is generally used in a form called a unit stack 2 in which a plurality of units 10 are stacked and arranged as shown in FIG. 2. As shown in the lower diagram of FIG. 3, the unit stack 2 is formed by sandwiching the sub-stack 200 from two sides with two end plates 220 and fastening the end plates 220 on both sides with a fastening mechanism 230. In FIG. 3, a unit stack 2 having a plurality of sub-stacks 200 is illustrated. The sub-stack 200 has a structure in which a plurality of layers are stacked in the order of the unit frame 3, the positive electrode 14, the separator 11, and the negative electrode 15 (refer to the upper diagram of FIG. 3), and supply and discharge are arranged at both ends of the stacked body The board 210 (refer to the lower diagram of FIG. 3 and omitted in FIG. 2). The outgoing piping 108, 109 and the returning piping 110, 111 of each circulation flow path 100P, 100N (refer FIG. 1, FIG. 2) are connected to the supply-discharge plate 210.

《Cell Frame》 As shown in the upper diagram of FIG. 3, the unit frame 3 includes a bipolar plate 31 disposed between the positive electrode 14 and the negative electrode 15, and a frame body 32 provided around the bipolar plate 31 (see also FIG. 4 ). On one side of the bipolar plate 31, the positive electrode 14 is arranged in a facing manner, and on the other side of the bipolar plate 31, the negative electrode 15 is arranged in a facing manner. A bipolar plate 31 is provided inside the frame body 32, and the concave portion 32o is formed by the bipolar plate 31 and the frame body 32. The concave portions 32o are formed on both sides of the bipolar plate 31, and the positive electrode 14 and the negative electrode 15 are accommodated in each concave portion 32o via the bipolar plate 31. Each recess 32o forms each cell space of the positive electrode unit 12 and the negative electrode unit 13 (refer to FIG. 1). The planar shape of each electrode of the positive electrode 14 and the negative electrode 15 is not particularly limited, and is rectangular in this embodiment. Moreover, the planar opening shape of the recess 32o is the same rectangular shape as the electrode, and the dimensions of the recess 32o and the electrode are substantially the same. Moreover, the area where each electrode in the bipolar plate 31 overlaps in the stacking direction (the effective electrode area where the bipolar plate 31 and the electrode 14 shown in FIG. 4 face each other) is rectangular.

The bipolar plate 31 is formed of plastic carbon, for example, and the frame 32 is formed of plastic such as vinyl chloride resin (PVC), polypropylene, polyethylene, fluororesin, epoxy resin, or the like. In the unit frame 3, the frame body 32 is integrated with the periphery of the bipolar plate 31 by injection molding or the like.

In the unit stack 2 (sub-stack 200), one face side and the other face side of the frame body 32 of adjacent unit frames 3 are butted against each other, between the bipolar plates 31 of adjacent unit frames 3, respectively Form 1 unit 10. When the unit 10 is assembled, the electrodes 14 and 15 are accommodated in the recesses 32o of the frame 32 in a compressed state in the thickness direction. An annular sealing member 37 such as an O-ring or a flat washer is disposed between the frame bodies 32 of each unit frame 3 to suppress leakage of electrolyte. A sealing groove 38 (see FIG. 4) in which a sealing member 37 is arranged is formed in the frame body 32.

The circulation of the electrolyte in the unit 10 is through the liquid supply manifolds 33, 34 and the discharge manifolds 35, 36 formed in the frame body 32 of the unit frame 3, and the liquid supply slit 33s formed in the frame body 32 , 34s and drainage slits 35s, 36s. In the case of the unit frame 3 (frame body 32) shown in this example, the positive electrode electrolyte is supplied from the liquid supply manifold 33 formed under the frame body 32 through the liquid supply slit formed on one side of the frame body 32 33s is supplied to the positive electrode 14, and is discharged to the drain manifold 35 through the drain slit 35s formed in the upper part of the frame 32. Similarly, the negative electrode electrolyte is supplied to the negative electrode 15 from the liquid supply manifold 34 formed on the lower portion of the frame 32 through the liquid supply slit 34s formed on the other surface side of the frame 32, and is formed through the frame 32. The upper liquid discharge slit 36s is discharged to the liquid discharge manifold 36. The liquid supply manifolds 33 and 34 and the liquid discharge manifolds 35 and 36 form a flow path of the electrolyte by stacking the unit frames 3. These flow paths are connected to the outgoing piping 108, 109 and the return piping 110, 111 of each circulation flow path 100P, 100N (see FIG. 1 and FIG. 2) via the supply and discharge plate 210 (see the lower diagram of FIG. 3). , The electrolyte can be circulated in the cell 10.

In the unit 10 shown in this example, the electrolyte is introduced from the lower side of the positive electrode 14 and the negative electrode 15 respectively, and the electrolyte is discharged from the upper side of each electrode 14, 15 and the electrolyte is directed upward from the lower edge of each electrode 14, 15 Edge flow. In the upper diagrams of FIG. 2 and FIG. 3, the arrows in each electrode 14, 15 indicate the overall flow direction of the electrolyte.

"Bipolar Plate" On the opposite surface of the bipolar plate 31 that faces the electrodes 14 and 15, as shown in FIG. 4, a flow path 4 for electrolyte circulation is formed. In this embodiment, the flow path 4 includes a plurality of grooves 5 (introduction grooves 51a to 51c and discharge grooves 52a to 52c). By forming the flow path 4 (groove 5) in the bipolar plate 31, the flow resistance of the electrolyte can be reduced. In FIG. 4, for ease of understanding, hatched portions are formed where the flow path 4 (groove 5) is not formed. One side of the bipolar plate 31 shown in FIG. 4 (positive side of the paper) is the opposite side facing the positive electrode 14, and the other side (back side of the paper) is the negative electrode 15 (refer to FIG. 3 and FIG. 4). (The illustration is omitted). In the bipolar plate 31 shown in FIG. 4, the lower side connected to the liquid supply slit 33 s is the introduction side of the positive electrolyte, and the upper side connected to the discharge slit 35 s is the discharge side of the positive electrolyte. In FIG. 4, the thick solid arrow on the left side of the paper indicates the direction of circulation of the entire electrolyte.

In FIG. 4, only one side of the bipolar plate 31 facing the positive electrode 14 is shown, but on the other side of the bipolar plate 31 facing the negative electrode 15, electrolysis is also formed in the same way as the one side The flow of liquid. The configuration of the flow path of the negative electrode electrolyte formed on the other surface side of the bipolar plate 31 is the same as that of the flow path 4 of the positive electrode electrolyte shown in FIG. 4, and therefore its description is omitted.

(Flow path) ＜Intake port and discharge port＞ The flow path 4 controls the distribution of the electrolyte that penetrates into the electrode 14, and is designed in such a way that the distribution of the electrolyte in the electrode 14 becomes uniform. The flow path 4 is provided with an introduction port 4i and a discharge port 4o of an electrolyte. The inlet 4i and the outlet 4o are connected to the liquid supply slit 33s and the liquid discharge slit 35s, respectively, the electrolyte is introduced from the inlet 4i through the liquid supply slit 33s, and the electrolyte is discharged from the outlet 4o to the drain Slit 35s. In this embodiment, the inlet 4i is located at the center of the lower side of the effective electrode area, and the outlet 4o is located at the center of the upper side of the effective electrode area.

＜Introduction and discharge path＞ The flow path 4 includes an introduction path 41 for introducing the electrolyte from the introduction port 4i, and a discharge path 42 for discharging the electrolyte to the discharge port 4o. The introduction path 41 and the discharge path 42 are independent of each other without communicating with each other. The introduction path 41 includes introduction grooves 51a to 51c, and the discharge path 42 includes discharge grooves 52a to 52c. When the flow path 4 includes the introduction path 41 and the discharge path 42, the electrolyte circulates so as to flow between the introduction path 41 and the discharge path 42. At this time, the electrolyte penetrates and diffuses into the electrode 14 to enable electrolysis The liquid spreads evenly over the entire electrode 14. As a result, the distribution of the electrolyte in the electrode 14 can be more effectively uniformed, and the reactivity of the electrode 14 and the electrolyte can be further improved.

<Rectifier> Furthermore, the introduction path 41 and the discharge path 42 are provided with rectifiers 510 and 520 connected to the introduction port 4i and the discharge port 4o, respectively. The rectifying portion 510 on the introduction side is formed along the lower edge of the bipolar plate 31, and the rectifying portion 520 on the discharge side is formed along the upper edge of the bipolar plate 31. The introduction path 41 is connected to the rectification part 510, and each of the introduction grooves 51a to 51c communicates with the introduction port 4i via the rectification part 510. The discharge path 42 is connected to the rectifying part 520, and each of the discharge grooves 52 a to 52 c communicates with the discharge port 4 o via the rectifying part 520. The rectifier 510 diffuses the electrolyte introduced from the inlet 4i along the lower edge of the bipolar plate 31, and introduces the electrolyte into the introduction path 41 (introduction grooves 51a to 51c) without any leakage. The rectifier 520 collects the electrolyte discharged from the discharge path 42 (discharge grooves 52a to 52c) to the discharge port 4o along the upper edge of the bipolar plate 31. The rectifiers 510 and 520 can efficiently introduce and discharge the electrolyte from the introduction port 4i and the discharge port 4o with respect to each of the introduction path 41 and the discharge path 42.

The flow path 4 shown in FIG. 4 becomes a line symmetry (left-right symmetry) with a center line connecting the inlet 4i and the outlet 4o (indicated by a single-dot chain line in the figure) as a symmetry axis, and further, on the inlet 4i side ( The lower side) is vertically asymmetric with the 4o side (upper side) of the discharge port. Since the flow path 4 is formed asymmetrically on the introduction side and the discharge side, the flow of the electrolyte on the discharge side where the pressure of the electrolyte is reduced can be improved.

(groove) The introduction grooves 51a to 51c constituting the introduction path 41 are connected to the rectifying portion 510 on the introduction side, extend from the introduction side (lower side) toward the discharge side (upper side), and the front end side of the discharge side becomes a closed end. The discharge grooves 52a to 52c constituting the discharge path 42 are connected to the rectifying portion 520 on the discharge side, extend from the discharge side (upper side) toward the introduction side (lower side), and the front end side of the introduction side becomes a closed end.

Each groove 5 (introduction grooves 51a to 51c and discharge grooves 52a to 52c) is opened on the opposite surface of the bipolar plate 31 to the electrode 14, and as shown in FIG. 4, the opening width of each groove 5 changes toward the front end side The small way is formed. In the case of the introduction grooves 51a to 51c, the opening width becomes smaller toward the front end side, and the pressure of the electrolyte becomes higher as it approaches the front end side, so that the electrolyte easily penetrates into the electrode 14 from the introduction grooves 51a to 51c. The "opening width" of the groove 5 refers to the width of the groove 5 orthogonal to the longitudinal direction.

The opening width (groove width) or depth (groove depth) of the groove 5 can be appropriately selected according to the size or thickness of the bipolar plate 31, and is not particularly limited. The groove width may be, for example, 0.2 mm or more and 10 mm or less, and further 0.5 mm or more and 5 mm or less, and the groove depth may be, for example, 0.5 mm or more and 5 mm or less, and further 1 mm or more and 3 mm or less.

As a method of forming the groove 5, for example, the surface of the bipolar plate 31 may be cut using a cutting tool such as an end mill. Alternatively, a convex portion corresponding to the shape of the groove 5 may be provided in the mold for forming the bipolar plate 31 in advance, and the groove 5 may be formed by mold molding such as injection molding.

<Ratio of contact area of electrodes> Set the contact area (the area of the hatched portion of the bipolar plate 31 shown in FIG. 4) of the bipolar plate 31 that faces the electrode 14 (ie, the effective electrode area) in contact with the electrode 14 as A, and set When the planar opening area of the groove 5 (the area of the hollow portion of the bipolar plate 31 shown in FIG. 4) is set to B, it is preferable that A/(A+B) exceeds 0.5 and does not reach 0.95. By the ratio of the contact area (A) of the electrode 14 to the area (A+B) of the opposing surface of the bipolar plate 31 [A/(A+B)] exceeding 0.5, the electrode 14 and the bipolar can be ensured The contact area of the plate 31 reduces the contact resistance between the electrode 14 and the bipolar plate 31. By this, the internal resistance (cell resistance) of the battery can be reduced. In addition, from the viewpoint of ensuring the formation area of the groove 5 in the opposing surface of the bipolar plate 31 (the flow path area of the electrolyte), the ratio of the contact area of the electrode 14 is preferably [A/(A+B) ] Less than 0.95, which can effectively reduce the flow resistance of the electrolyte. The ratio [A/(A+B)] of the contact area of the electrode 14 is more preferably 0.6 or more and 0.9 or less, and further 0.7 or more and 0.8 or less. The "planar opening area" of the groove 5 refers to the opening area of the groove 5 in the opposing surface when looking down on the bipolar plate 31.

<section shape> FIG. 6 shows the cross-sectional shape of the groove 5 in this embodiment. In this embodiment, as shown in FIG. 6, in the cross section of the groove 5 orthogonal to the flow direction of the electrolyte, the width of the opening 56 side of the groove 5 is more than the width of the bottom 57 side. The cross-sectional shape is formed into a tapered shape from the opening 56 side toward the bottom 57 side. Therefore, since the width of the opening 56 side of the groove 5 is more than the width of the bottom 57 side, it is easier to form the groove 5 than the case where the width of the bottom 57 side is wider than the width of the opening 56 side. In addition, when the cross-sectional shape of the groove 5 (particularly the introduction grooves 51a to 51c) is formed into a tapered shape from the opening 56 side toward the bottom 57 side, it is easy to allow the electrolyte solution to penetrate into the electrode from the groove 5. Examples of the cross-sectional shape of the groove 5 include a rectangular shape, a triangular shape (V-shape), a trapezoid shape, a semicircular shape, a semi-elliptical shape, and the like.

<Dendritic groove> In the tank 5 shown in FIG. 4, the introduction tanks 51a, 51c and the discharge tanks 52a, 52c are formed as dendritic branch-shaped tanks, and include a main tank section 60 and at least one branch tank branched from the main trunk section 60部61. By forming at least one of the grooves 5 in a dendritic shape, it is easy to permeate and diffuse the electrolyte over a large area in the electrode 14 and the distribution of the electrolyte in the electrode 14 can be made more uniform. Therefore, the reactivity of the electrode 14 and the electrolytic solution can be further improved. The "main trough part" mentioned here refers to a trough part directly or indirectly connected to the inlet 4i or the outlet 4o through the rectifiers 510 and 520. "Branch groove portion" refers to a groove portion branched from the main trunk groove portion 60 and having an opening width smaller than that of the trunk groove portion 60.

Furthermore, the branch groove portion 61 may have a branch groove portion 62 further branched from the branch groove portion 61 like the introduction groove 51c and the discharge groove 52a. By having the branch groove portion 62 branching further from the branch groove portion 61, it is easy to effectively permeate and diffuse the electrolyte into the electrode 14. Here, the branch groove portion 61 is referred to as a primary branch groove, and the branch groove portion 62 is referred to as a secondary branch groove. In this embodiment, the opening width of the branch groove portion 62 (secondary branch groove) after branching is smaller than the opening width of the branch groove portion 61 (primary branch groove) before branching.

FIG. 5 shows a cut-away view of the introduction groove 51c. Taking the introduction groove 51c as an example, the relationship between each of the trunk groove portion 60 and the branch groove portion 61, and the branch groove portion 61 and the branch groove portion 62 will be described. As shown in FIG. 5, in the portion where the branch groove portion 61 branches from the main trunk portion 60, the opening width (W _a1 ) of the branch groove portion 61 is smaller than the opening width (W _a0 ) of the main trunk portion 60. In addition, at a portion where the branch groove portion 62 branches from the branch groove portion 61, the opening width (W _a2 ) of the branch groove portion 62 is smaller than the opening width (W _b1 ) of the branch groove portion 61. Since the opening width of the branch groove portions 61 and 62 of the branches gradually decreases each time the branches pass, the contact area between the electrode 14 and the bipolar plate 31 is increased, and the distance between the electrode 14 and the bipolar plate 31 can be reduced Contact resistance.

<Number of branches> In the dendritic tank described above, when the number of branches of the branch groove portion is set to N (N: natural number), N is preferably 3 or less. The "branch frequency" mentioned here refers to the number of times that the branch of the trunk is counted from the main trunk. For example, in the introduction tank 51c or the discharge tank 52a, the number N of branches of the branch groove portion 61 branching from the main trunk portion 60 is 1, and the number of branches N of the branch groove portion 62 branching further from the branch groove portion 61 is 2. Assuming that there is another branch groove portion that branches further from the branch groove portion 62, the branching frequency N is 3. In the present embodiment, by repeating branching of the main trunk groove portion 60, the groove width (opening width) of the branched branch groove portions 61 and 62 is reduced and narrowed. As in the present embodiment, by limiting the number of branches N to 3 or less, it is possible to avoid excessive narrowing of the groove width of the branch groove portions 61 and 62 due to branching.

Furthermore, in this embodiment, as shown in FIG. 4, for example, in the introduction groove 51 c or the discharge groove 52 a, the branch groove portion 61 intersects the main groove portion 60 non-orthogonally. Since the branch groove portion 61 intersects the main groove portion 60 non-orthogonally, compared to the case where the branch groove portion 61 and the main groove portion 60 are orthogonal, the flow resistance of the electrolyte can be reduced. “Non-orthogonal intersection” refers to a case where the inclination angle α (see FIG. 5) of the extending direction of the branch groove portion 61 with respect to the extending direction of the main groove portion 60 is an acute angle. The inclination angle α is, for example, 10° or more and 80° or less.

<counter comb area> In the present embodiment, the introduction grooves 51a to 51c of the introduction path 41 and the discharge grooves 52a to 52c of the discharge path 42 are opposed to each other and are arranged in opposite comb tooth regions. Furthermore, in the case of the flow path 4 shown in FIG. 4, for example, the branch groove portions 61 of the introduction groove 51a and the branch groove portions 62 of the discharge groove 52a are alternately arranged opposite to each other, and these also form the opposite comb teeth area. Since the flow path 4 has the opposite comb-tooth area, the amount of electrolyte flowing through the introduction path 41 (introduction grooves 51a to 51c) and the discharge path 42 (discharge grooves 52a to 52c) increases to the electrode 14 The electrolyte penetration and diffusion increases. Thereby, the reaction efficiency of the electrode 14 and the electrolyte can be improved.

<convex part> When at least a part of the groove 5 has a wide portion with an opening width of 2 mm or more, a convex portion 59 protruding from the bottom may be formed in the wide portion. By providing the convex portion 59 in the wide portion of the groove 5, it is possible to suppress the electrode 14 from being buried in the groove 5. In this embodiment, as shown in FIG. 4, the base end side (the side connected to the rectifying portions 510 and 520) of each of the introduction groove 51 a and the discharge groove 52 a partially becomes a wide portion, and a convex portion is provided at this portion Department 59. The shape of the convex portion 59 in a plan view is not particularly limited, and various shapes such as a polygonal shape such as a triangle or a quadrangle, a round shape, or an ellipse shape can be used. In addition, the number of the convex portions 59 arranged in the wide portion may be one, or plural.

<curve section> One of the characteristics of this embodiment is that at least one of the grooves 5 has a curved portion. "Curved part" refers to a part that is curved in the longitudinal direction of the groove 5, and is typically a non-periodic curve. In the present embodiment, for example, the branch groove portions 61, 62 of the introduction groove 51c or the branch groove portions 61, 62 of the discharge groove 52a are formed by bending, and each is constituted by a curved portion. The radius of curvature of the curved portion may be, for example, 0.1 mm or more, further 1 mm or more, and further 3 mm or more.

[Effect of the embodiment] The bipolar plate 31 of the above-mentioned embodiment can reduce the resistance to the flow of the electrolyte by forming the electrolyte flow path 4 on the opposite surface to the electrode 14 and can control the penetration of the electrolyte into the electrode 14 distributed. Furthermore, since at least one of the grooves 5 constituting the flow path 4 has a curved portion, the degree of freedom of layout is improved compared to a linear groove, so that the distribution of the electrolyte in the electrode 14 becomes uniform地Configuration槽5. Thereby, the uniformity of the distribution of the electrolyte in the electrode 14 can be sufficiently improved to improve the reactivity of the electrode 14 and the electrolyte. Therefore, the bipolar plate 31 can reduce the flow resistance of the electrolyte, and can improve the reactivity of the electrode 14 and the electrolyte. Therefore, when the bipolar plate 31 of the embodiment is used in the RF battery 1, the pressure loss due to the flow resistance of the electrolyte can be reduced, and the reaction resistance in the electrode 14 can be reduced. Therefore, the battery can be reduced Internal resistance (cell resistance).

When the tank 5 has a curved portion, the direction of the electrolyte flowing in the tank 5 can be smoothly changed. Compared with the case where the electrolyte is bent at a right angle or an acute angle, the electrolyte flows smoothly, thereby easily reducing the flow resistance .

By including the above-mentioned bipolar plate 31, the unit frame 3 of the embodiment can reduce the flow resistance of the electrolyte, and can increase the reactivity of the electrode 14 and the electrolyte, so that the pressure loss due to the flow resistance of the electrolyte can be reduced. And the reaction resistance in the electrode 14 can be reduced.

By including the above-mentioned unit frame 3, the unit stack 2 of the embodiment can reduce the pressure loss due to the flow resistance of the electrolyte, and can also reduce the reaction resistance in the electrode 14.

The RF battery 1 of the embodiment can reduce the pressure loss due to the flow resistance of the electrolyte and reduce the reaction resistance in the electrode 14 due to the above-mentioned cell stack 2, so the internal resistance (cell resistance) of the battery can be reduced .

[Variation] Referring to Fig. 7, a modification of the bipolar plate 31 will be described. In the bipolar plate 31 shown in FIG. 7, the configuration of the electrolyte flow path 4 is different from the bipolar plate 31 of the embodiment shown in FIG. 4 described above. The following description will focus on the differences from the above embodiment.

The effective electrode area of the bipolar plate 31 shown in FIG. 7 is rectangular. In a modified example, as shown in FIG. 7, the inlet 4i is located at the lower right corner of the effective electrode area, the outlet 4o is located at the upper left corner of the effective electrode area, and the inlet 4i and the outlet 4o are located diagonally to the effective electrode area position. Furthermore, in a modified example, as the rectifying portion connected to the introduction side of the inlet 4i, there is a rectifying portion 510 formed along the lower edge of the bipolar plate 31 and a rectifying portion formed along the right edge of the bipolar plate 31部511. As the rectifying portion connected to the discharge side of the discharge port 4o, there are a rectifying portion 520 formed along the upper edge of the bipolar plate 31 and a rectifying portion 521 formed along the left edge of the bipolar plate 31. The rectifying parts 510 and 511 on the introduction side and the rectifying parts 520 and 521 on the discharge side are formed so as not to communicate with each other.

The flow path 4 shown in FIG. 7 includes an introduction path 41 and a discharge path 42. The introduction path 41 includes introduction grooves 51 a to 51 d connected to the rectification portions 510 and 511 on the introduction side, and the discharge path 42 includes discharge grooves 52 a to 52 d connected to the rectification portions 520 and 521 on the discharge side. Among these grooves, the introduction grooves 51c and 51d and the discharge groove 52c are formed as a dendritic dendritic groove, and are provided with a trunk groove portion 60 and a branch groove portion 61 branched from the autonomous trunk groove portion 60. For example, in the introduction grooves 51c, 51d or the discharge groove 52c, the branch groove portion 61 intersects the main groove portion 60 non-orthogonally. Also, for example, the branch groove portion 61 of the introduction grooves 51c, 51d or the branch groove portion 61 of the discharge groove 52c has a curved portion.

The flow path 4 becomes symmetrical with a line connecting a diagonal line (indicated by a single-dot chain line in the figure) connecting the introduction port 4i and the discharge port 4o. Moreover, the angle formed by the diagonal lines of the rectifying portions 510 and 520 and the effective electrode region (the diagonal line connecting the inlet 4i and the outlet 4o) is 40° or more and 50° or less. By setting the angle formed by each of the rectifying portions 510 and 520 and the diagonal of the effective electrode region within the above range, the pressure loss in the rectifying portions 510 and 520 can be reduced.

In a modified example, as shown in FIG. 7, there is an intermediate groove 54 that is not connected to the introduction path 41 and the discharge path 42. The intermediate groove 54 is an independent closed groove that does not communicate with the rectifying portions 510 and 511 on the introduction side and the rectifying portions 520 and 521 on the discharge side, and the introduction grooves 51a to 51d and the discharge grooves 52a to 52d. The intermediate groove 54 is a dendritic groove that extends along the above-mentioned diagonal line and is formed into a dendritic shape from the middle portion in the longitudinal direction toward both ends. In detail, the branch groove which has each branch part of the main groove part 60 located in the middle part of the longitudinal direction of the intermediate groove 54, the introduction side (lower right side), and the discharge side (upper left side) of the main dry groove part 60 is respectively branched Branch 61, and branch groove portion 62 branching further from each branch groove portion 61. In the intermediate groove 54, the branch groove portion 61 intersects the main groove portion 60 non-orthogonally, and the branch groove portions 61 and 62 have curved portions.

The flow path 4 shown in FIG. 7 has, in addition to the opposed comb-tooth area formed by the introduction grooves 51c and 51d and the discharge grooves 52c and 52d, it also has the introduction grooves 51a to 51c or the discharge grooves 52a to 52c and the intermediate groove 54 forms the opposite comb-tooth area. By forming the opposing comb-tooth area using three of the introduction grooves 51a to 51d, the discharge grooves 52a to 52d and the intermediate groove 54, it is easy to spread the electrolyte over a larger area of the electrode, and it is easy to make the electrolyte in the electrode The distribution is more uniform.

Furthermore, in a modified example, the main groove portion 60 of the introduction groove 51 a and the intermediate groove 54 each has a wide width portion, and the convex portion 59 is arranged in each wide width portion.

[Test Example 1] A bipolar plate corresponding to the embodiment in which the flow path of the electrolyte is formed was fabricated, an RF battery was assembled using the bipolar plate, and the cell resistivity was investigated.

In Test Example 1, the grooved bipolar plates of Sample No. 1 to No. 3 with flow paths formed as shown in FIGS. 8A to 8C were prepared. The material of the bipolar plate is plastic carbon. The bipolar plates of samples No. 1 to No. 3 have the same shape and size, only the flow path is different, and the electrode contact area A in the opposing surface of the electrode and the plane opening area B of the groove constituting the flow path are different. The area (A+B) of the opposite surface of each bipolar plate is the same and is 891 mm ² (27 mm×33 mm). The ratio [A/(A+B)] of the electrode contact area A of the bipolar plate and the electrode contact area (A) in the area of the opposite surface (A+B) in each sample is shown in the table 1. In addition, the numerical value of the electrode contact area ratio [A/(A+B)] shown in Table 1 is the value after rounding off the 3rd decimal place.

Use sample No.1~No.3 bipolar plates to assemble a single unit RF battery. The single unit is equipped with positive and negative electrodes on both sides of the diaphragm, and is manufactured by clamping the unit frame with bipolar plates from both sides. Carbon electrodes are used for the positive and negative electrodes.

(Measurement of cell resistivity) A single cell RF battery using bipolar plates of each sample was subjected to a charge and discharge test under the test conditions shown below. Furthermore, the cell resistivity (Ω·cm ² ) at the time of 3 cycles of charge and discharge was obtained. Table 1 shows the cell resistivity of each sample. The cell resistivity is calculated according to the calculation formula shown below.

<Test conditions>"Electrolyte" Vanadium sulfate aqueous solution (V concentration: 1.7 mol/L, sulfuric acid concentration: 3.4 mol/L) "Electrolyte flow rate" Inlet flow rate: 0.31 (mL/min) Outlet flow rate: free flow "Charge and discharge Conditions>> Charge and discharge method: constant current Current density: 70 (mA/cm ² ) End-of-charge voltage: 1.55 (V) End-of-discharge voltage: 1.00 (V) Temperature: 25°C <unit resistivity> Formula: R=(V2- V1)/2I R: unit resistivity (Ω·cm ² ) I: current density (A/cm ² ) V1: voltage at the intermediate time point of charging time (V) V2: voltage at the intermediate time point of discharging time (V )

[Table 1]

As shown in Table 1, the cell resistivities of samples No. 1 to No. 3 decrease in the order of No. 1>No. 2>No. 3, and samples No. 2, No. 3 and sample No. Compared with 1, the cell resistivity can be greatly reduced. From this result, it can be seen that the ratio [A/(A+B)] of the electrode contact area preferably exceeds 0.5.

1‧‧‧Redox flow battery (RF battery) 2‧‧‧ unit stack 3‧‧‧ unit frame 4‧‧‧ flow path 4i‧‧‧ inlet port 4o‧‧‧ discharge port 5‧‧‧ tank 10‧ ‧‧Unit 11‧‧‧Separator 12‧‧‧Positive unit 13‧‧‧Negative unit 14‧‧‧Positive electrode 15‧‧‧Negative electrode 31‧‧‧Bipolar plate 32‧‧‧Frame 32o‧‧‧Concave part 33‧‧‧Liquid supply manifold 33s‧‧‧Liquid supply slit 34‧‧‧Liquid supply manifold 34s‧‧‧Liquid supply slit 35‧‧‧Drainage manifold 35s‧‧‧Drainage slit 36‧ ‧‧Drain manifold 36s‧‧‧Drain slit 37‧‧‧Sealing member 38‧‧‧Seal groove 41‧‧‧Introduction path 42‧‧‧Exhaust path 51a‧‧‧Introduction groove 51b‧‧‧Introduction groove 51c‧‧‧Introduction groove 51d‧‧‧Introduction groove 52a‧‧‧Exhaust groove 52b‧‧‧Exhaust groove 52c‧‧‧Exhaust groove 52d‧‧‧Exhaust groove 54‧‧‧‧Intermediate groove 56‧‧‧Open part 57‧ ‧‧Bottom 59‧‧‧Convex part 60‧‧‧Main trough part 61‧‧‧Branch trough part (primary branch trough) 62‧‧‧Branch trough part (secondary branch trough) 100N‧‧‧Negative electrode circulation 100P‧‧‧Positive cathode flow channel 106‧‧‧Positive electrolyte tank 107‧‧‧Negative electrolyte tank 108,109‧‧‧Outline piping 110,111‧‧‧Return piping 112,113‧‧‧Pump 200‧ ‧‧Sub-stack 210‧‧‧Supply and discharge plate 220‧‧‧End plate 230‧‧‧Clamping mechanism 510‧‧‧Rectifier (introduction side) 511‧‧‧Rectifier (introduction side) 520‧‧‧Rectifier (Discharge side) 521‧‧‧Rectifier (discharge side) C‧‧‧AC/DC converter P‧‧‧Power system W _a0 ‧‧‧ opening width W _a1 ‧‧‧ opening width W _a2 ‧‧‧ opening width W _b1 ‧‧‧ opening width α‧‧‧ inclination angle

FIG. 1 is an operation principle diagram of the redox flow battery of the embodiment. 2 is a schematic configuration diagram showing an example of the redox flow battery of the embodiment. Fig. 3 is a schematic configuration diagram showing an example of a unit stack according to an embodiment. 4 is a schematic plan view of a unit frame equipped with a bipolar plate according to an embodiment when viewed from one side of a bipolar plate. FIG. 5 is an enlarged view showing one of the tanks constituting the flow path of the electrolyte shown in FIG. 4 withdrawn. 6 is a schematic cross-sectional view schematically showing the cross-sectional shape of the groove in the embodiment. 7 is a schematic plan view showing a modified example of the bipolar plate of the embodiment. 8A is a plan view showing the bipolar plate of sample No. 1 used in Test Example 1. FIG. 8B is a plan view showing the bipolar plate of sample No. 2 used in Test Example 1. FIG. 8C is a plan view showing the bipolar plate of sample No. 3 used in Test Example 1. FIG.

3‧‧‧ unit frame

4‧‧‧Flow

4i‧‧‧Import

4o‧‧‧Exhaust

5‧‧‧slot

14‧‧‧Positive electrode

31‧‧‧bipolar plate

32‧‧‧frame

33, 34‧‧‧ Liquid supply manifold

33s, 34s‧‧‧ liquid supply slit

35、36‧‧‧Drain manifold

35s, 36s‧‧‧Discharge slit

38‧‧‧Seal groove

41‧‧‧ Leading way

42‧‧‧Exhaust

51a‧‧‧Introduction slot

51b‧‧‧Introduction slot

51c‧‧‧Introduction slot

52a‧‧‧Discharge slot

52b‧‧‧Discharge slot

52c‧‧‧Discharge slot

59‧‧‧Convex

60‧‧‧trunk trough

61‧‧‧Branch trough (1st branch trough)

62‧‧‧Branch trough (second branch trough)

510‧‧‧Rectifier (introduction side)

520‧‧‧rectifier (discharge side)

Claims (19)

A bipolar plate for providing electrodes for a redox flow battery, having an opposing surface facing the electrode, and having at least one groove forming a flow path for the electrolyte to circulate on the opposing surface, and When looking down on the bipolar plate, at least one of the grooves has a curved portion. As in the bipolar plate of claim 1, the radius of curvature of the above-mentioned curve is 0.1 mm or more. The bipolar plate according to claim 1, wherein the opening width of the above-mentioned groove becomes smaller toward the front end side. According to the bipolar plate of claim 1, wherein the contact area of the opposing surface of the bipolar plate that is in contact with the electrode is A, and the planar opening area of the groove is B, A/(A+B ) Exceeds 0.5 and does not reach 0.95. The bipolar plate according to claim 1, wherein in the cross section of the groove orthogonal to the flow direction of the electrolyte, the width of the opening side of the groove is more than the width of the bottom side. The bipolar plate according to claim 5, wherein the cross-sectional shape of the groove is formed into a tapered shape from the opening side toward the bottom side. The bipolar plate according to claim 1, wherein the groove is formed in a dendritic shape, and includes a trunk groove portion and at least one branch groove portion branched from the trunk groove portion, and At least one of the branch groove portions intersects the main groove portion non-orthogonally. The bipolar plate according to claim 7, wherein at least one of the branch groove portions has the curved portion. The bipolar plate according to claim 7, wherein at least one of the branch groove portions has a branch groove portion further branched from the branch groove portion. According to the bipolar plate of claim 9, where the number of branches of the branch groove portion is set to N (N: natural number), N is 3 or less. The bipolar plate according to claim 9, wherein the opening width of the branch groove portion after branching is smaller than the opening width of the branch groove portion before branching. As in the bipolar plate of claim 1, where The above flow path has: The inlet and outlet of the above electrolyte; An introduction path that introduces the electrolyte from the inlet; and The discharge path, which is independent of the introduction path and is independent, discharges the electrolyte to the discharge port; The introduction path and the discharge path each include at least one of the grooves, and At least one of the introduction path and the discharge path includes a rectifying portion connected to the introduction port or the discharge port and formed along the edge of the bipolar plate. The bipolar plate according to claim 12, wherein the effective electrode area facing the bipolar plate and the electrode is rectangular, and the introduction port and the discharge port are provided at diagonal positions of the effective electrode area, and The angle formed by the rectifying portion and the diagonal of the effective electrode region is 40° or more and 50° or less. The bipolar plate according to claim 12, wherein in the bipolar plate, the inlet port side is set to the lower side and the outlet port side is set to the upper side, The above flow path is asymmetrical. The bipolar plate according to claim 12 has opposing comb-tooth regions where the grooves of the introduction path and the grooves of the discharge path are alternately arranged opposite to each other. The bipolar plate according to claim 1, wherein at least a part of the groove has a wide portion with an opening width of 2 mm or more, and a convex portion protruding from the bottom is formed in the wide portion. A unit frame including the bipolar plate according to any one of claims 1 to 16, and a frame provided on the outer periphery of the bipolar plate. A unit stack having a unit frame as in claim 17. A redox flow battery provided with the unit stack according to claim 18.

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