WO2019234868A1 - Bipolar plate, cell frame, cell stack, and redox flow battery - Google Patents

Abstract

A bipolar plate that has a facing surface facing an electrode of a redox flow battery, and an electrolytic solution introduction section and discharge section positioned on the facing surface, said bipolar plate comprising: an introduction path that has a groove section CI₀ connecting to the introduction section and a groove section CI_n branching off from the groove section CI₀, neither of said grooves connecting to the discharge section; and a discharge path that has a groove section CO₀ connecting to the discharge section and a groove section CO_m branching off from the groove section CO₀, neither of said grooves connecting to the introduction section, wherein the groove section CI_n branches off from a groove section CI_n-1 in a direction intersecting the direction of extension of the groove section CI_n-1, the groove section CO_m branches off from a groove section CO_m-1 in a direction intersecting the direction of extension of the groove section CO_m-1, and when the bipolar plate is in planar view, tip end sections of all of the grooves are tapered. Here, n and m are arbitrary natural numbers greater than or equal to 1.

Description

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

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

As one of large-capacity storage batteries, a redox flow battery (hereinafter sometimes referred to as “RF battery”) is known (see, for example, Patent Documents 1 and 2). In general, an RF battery uses a cell stack in which a plurality of cell frames, positive electrodes, diaphragms, and negative electrodes are stacked. The cell frame includes a bipolar plate disposed between the positive electrode and the negative electrode, and a frame provided on the outer periphery of the bipolar plate. In the cell stack, positive and negative electrodes are arranged between bipolar plates of adjacent cell frames with a diaphragm interposed therebetween to form one cell. The RF battery performs charging / discharging by circulating an electrolyte solution in a cell containing an electrode by a pump.

Patent Documents 1 and 2 describe that a channel is formed by forming a plurality of grooves through which an electrolytic solution flows on the electrode side surface of a bipolar plate.

JP2015-122230A JP 2015-210849 A

The bipolar plate of the present disclosure is
A bipolar plate having a facing surface facing an electrode of a redox flow battery, and an introduction portion and a discharging portion for an electrolyte solution disposed on the facing surface,
A groove portion CI _n branching from the groove portion CI _0, and the groove CI ₀ to be connected to the inlet portion, and the introduction groove not connect any of the grooves in the discharge portion,
A groove portion CO ₀ connected to the discharge portion, and a groove portion CO _m branched from the groove portion CO ₀ , each of the groove portions including a discharge groove not connected to the introduction portion,
Groove CI _n branches in a direction crossing the extending direction of the groove _{CI n-1} from the groove _{CI n-1,}
Groove CO _m branches in a direction crossing the extending direction of the groove _{CO m-1} from the groove _{CO m-1,}
When the bipolar plate is viewed in plan, the tip of each groove is tapered.
However, n and m are 1 or more arbitrary natural numbers.

The cell frame of the present disclosure is
The bipolar plate of the present disclosure and a frame body provided on the outer periphery of the bipolar plate.

The cell stack of the present disclosure is
The cell frame of the present disclosure is provided.

The redox flow battery of the present disclosure is
The cell stack of the present disclosure is provided.

It is an operation principle figure of the redox flow battery concerning an embodiment. It is a schematic block diagram which shows an example of the redox flow battery which concerns on embodiment. It is a schematic block diagram which shows an example of the cell stack which concerns on embodiment. It is a schematic plan view when a cell frame provided with the bipolar plate which concerns on embodiment is planarly viewed from the one surface side of the bipolar plate. It is an enlarged view which extracts and shows a part of flow path of the electrolyte solution shown in FIG. It is a schematic sectional drawing which shows typically the cross-sectional shape of the groove | channel in embodiment. It is a schematic plan view which shows the modification of the bipolar plate which concerns on embodiment. Sample No. used in Test Example 1 It is a top view which shows 1 bipolar plate. Sample No. used in Test Example 1 It is a top view which shows 2 bipolar plates. Sample No. used in Test Example 1 3 is a plan view showing a bipolar plate 3. FIG.

[Problems to be solved by the present disclosure]
Further improvement of the battery performance of the redox flow battery is desired. From the viewpoint of improving the battery performance, it is required to reduce the internal resistance (cell resistance) of the battery. As a factor of the internal resistance, there are a flow state of the electrolytic solution, for example, a flow resistance of the electrolytic solution, a reaction resistance at the electrode, and the like.

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. A porous material such as carbon felt made of carbon fiber is usually used for the electrode, and an electrolytic solution flows in the electrode. When a flow path having a groove through which the electrolytic solution flows is provided on the electrode side surface of the bipolar plate, the flow resistance of the electrolytic solution can be reduced, and the pressure loss due to the flow resistance of the electrolytic solution can be reduced. Further, by using a bipolar plate having a channel having a groove, the flow of the electrolyte solution penetrating into the electrode can be controlled, and the distribution of the electrolyte solution in the electrode can be suppressed from becoming non-uniform. By suppressing variations in the distribution of the electrolyte solution penetrating into the electrode, the reactivity between the electrode and the electrolyte solution can be improved, and the reaction resistance at the electrode can be reduced.

However, in the past, it has not been said that sufficient studies have been made to reduce the internal resistance after sufficiently considering the flow state of the electrolyte solution at the electrode. In the conventional bipolar plate, since the flow path is mainly composed of linear grooves, the degree of freedom in the layout of the grooves is low, and it is difficult to sufficiently improve the uniformity of the distribution of the electrolyte in the electrodes. There is room for improving the reactivity between the electrode and the electrolyte.

Therefore, an object of the present disclosure is to provide a bipolar plate that can improve the reactivity between the electrode and the electrolyte while reducing the flow resistance of the electrolyte. Another object of the present disclosure is to provide a cell frame and a cell stack that can improve battery performance. Furthermore, an object of the present disclosure is to provide a redox flow battery having excellent battery performance.

[Effects of the present disclosure]
According to the present disclosure, it is possible to provide a bipolar plate that can improve the reactivity between the electrode and the electrolytic solution while reducing the flow resistance of the electrolytic solution. Moreover, according to this indication, the cell frame and cell stack which can improve battery performance can be provided. Furthermore, according to the present disclosure, a redox flow battery having excellent battery performance can be provided.

[Description of Embodiment of Present Invention]
First, the contents of the embodiments of the present invention will be listed and described.

(1) The bipolar plate according to the embodiment is
A bipolar plate having a facing surface facing an electrode of a redox flow battery, and an introduction portion and a discharging portion for an electrolyte solution disposed on the facing surface,
A groove portion CI _n branching from the groove portion CI _0, and the groove CI ₀ to be connected to the inlet portion, and the introduction groove not connect any of the grooves in the discharge portion,
A groove portion CO ₀ connected to the discharge portion, and a groove portion CO _m branched from the groove portion CO ₀ , each of the groove portions including a discharge groove not connected to the introduction portion,
Groove CI _n branches in a direction crossing the extending direction of the groove _{CI n-1} from the groove _{CI n-1,}
Groove CO _m branches in a direction crossing the extending direction of the groove _{CO m-1} from the groove _{CO m-1,}
When the bipolar plate is viewed in plan, the tip of each groove is tapered.
However, n and m are 1 or more arbitrary natural numbers.

The introduction groove shown in the above definition is formed in a tree shape with the groove part CI ₀ as a trunk and the groove part CI _n as a branch. It can be said that the introduction groove is formed in a tree shape also in that the tip of each groove part of the introduction groove is tapered. Similarly, the discharge groove is formed in a tree shape with the groove portion CO ₀ as a trunk and the groove portion CO _m as a branch, and the discharge groove has a tree shape in that the tip of each groove portion of the discharge groove is tapered. It can be said that it is formed.

By providing a tree-like introduction groove and discharge groove that are independent of each other on the opposite surface of the bipolar plate, the electrolyte solution can be quickly dispersed in the plane direction of the bipolar plate, so that the flow resistance of the electrolyte solution can be reduced. At the same time, it is easy to distribute the electrolyte uniformly throughout the electrode. In particular, since the groove width in each groove portion of the introduction groove becomes smaller toward the tip side, the pressure of the electrolyte solution increases as it approaches the tip side, and the electrolyte solution easily penetrates and diffuses from the groove portion into the electrode. Furthermore, since the groove width in each groove portion of the discharge groove is reduced toward the tip side, it is possible to suppress the electrolyte from moving excessively from the electrode to the discharge groove, and it is discharged to the discharge groove without reacting with the electrode. The amount of electrolyte solution can be reduced. As described above, according to the bipolar plate of the embodiment, the electrolyte can be uniformly distributed to the electrode, and the reactivity between the electrode and the electrolyte can be improved, so that the internal resistance (cell resistance) of the redox flow battery can be improved. Can be reduced.

(2) As one form of the bipolar plate,
The form which has an opposing comb-tooth area | region where the one part groove part of the said introduction groove | channel and the one part groove part of the said discharge groove mutually mesh | engage is mentioned.

Opposing comb teeth regions where a part of the introduction groove and a part of the discharge groove mesh with each other, i.e., a part of the introduction groove and a part of the discharge groove are alternately arranged facing each other. By forming the formed region, the amount of the electrolytic solution flowing so as to cross between the introduction groove and the discharge groove can be increased. As a result, the electrolyte solution that permeates and diffuses into the electrode can be increased, and the reaction efficiency between the electrode and the electrolyte solution can be increased. The opposing comb-tooth region only needs to be on at least a part of the opposing surface of the bipolar plate, and there may be a portion where the groove portion of the introduction groove and the groove portion of the discharge groove are not alternately arranged.

(3) As one form of the bipolar plate,
An intermediate groove not connected to any of the introduction part, the discharge part, the introduction groove, and the discharge groove;
The intermediate groove has a groove part CC ₀ extending from the introduction part side toward the discharge part side, and a groove part CC _k branched from the groove part CC ₀ ,
Groove CC _k branches in a direction crossing the extending direction of the groove _{CC k-1} from the groove _{CC k-1,}
When the bipolar plate is viewed in plan, the shape of the tip of any groove may be narrower than the width of other portions.
However, k is an arbitrary natural number of 1 or more.

</ RTI> By forming the intermediate groove in addition to the introduction groove and the discharge groove, the electrolyte can be more quickly dispersed over the entire surface of the electrode. As a result, it is possible to reduce the flow resistance of the electrolytic solution and to make the distribution of the electrolytic solution more uniform.

(4) As one form of the bipolar plate of (3) above,
Having a counter comb tooth region in which a part of the groove part of the introduction groove and a part of the groove part of the intermediate groove mesh with each other;
The form which has an opposing comb-tooth area | region where the one part groove part of the said discharge groove and the one part groove part of the said intermediate groove mutually mesh | engage is mentioned.

By forming the opposed comb tooth region, it is possible to increase the amount of the electrolyte flowing so as to cross between the introduction groove and the intermediate groove and between the intermediate groove and the discharge groove. As a result, the electrolyte solution that permeates and diffuses into the electrode can be increased, and the reaction efficiency between the electrode and the electrolyte solution can be increased.

(5) As one form of the bipolar plate,
Examples include a form in which all the groove portions are non-linear and the groove widths are randomly changed.

The groove has the largest groove width at the base and the narrowest groove width at the tip. The groove width of the groove part may be gradually narrowed from the root of the groove part toward the tip, or may be locally widened in the middle. The said structure has shown that the introduction groove | channel and the discharge groove | channel are formed in more organic dendritic shape. By using such organic dendritic introduction grooves and discharge grooves, the electrolyte can be easily dispersed uniformly over the entire surface of the electrode.

(6) As one form of the bipolar plate,
The total area of the groove CI _n when bipolar plate in a plan view, the groove CI less than the total area of the _n-1, and the total area of the groove CO _m in a plan view the bipolar plate groove CO _{m- A} form smaller than the total area of ₁ is mentioned.

The above configuration is a configuration in which the opening area of the groove portion decreases step by step each time a branch is made. In the introduction groove, after the electrolyte solution is quickly spread to every corner of the introduction groove, the electrolyte solution easily penetrates and diffuses from each groove portion to the electrode. Further, in the discharge groove, the electrolyte solution is prevented from excessively moving from the electrode to each groove portion, and the reactivity between the electrode and the electrolyte solution is improved, and the electrolyte solution collected in each groove portion is quickly guided to the outlet. Thereby, the distribution | circulation resistance of electrolyte solution can be reduced.

(7) As one form of the bipolar plate,
The introduction part includes an inlet of the electrolyte solution in the bipolar plate, and an introduction side rectification part formed along the edge of the bipolar plate from the inlet,
The said discharge part is a form provided with the exit of the said electrolyte solution in the said bipolar plate, and the discharge side rectification | straightening part formed along the edge of the said bipolar plate from the said exit.

By providing the introduction side rectification unit in the introduction part, the electrolyte introduced from the inlet can be efficiently diffused into the introduction groove. Further, by providing the discharge side rectification unit in the discharge unit, the electrolyte solution can be efficiently recovered from the discharge groove and the electrolyte solution can be discharged from the outlet.

(8) As one form of the bipolar plate of (7),
Of the opposed surfaces, the effective electrode region that actually faces the electrode is rectangular,
The inlet and the outlet are provided at diagonal positions of the effective electrode region;
The form which the angle which the said introduction side rectification part and the said discharge side rectification part and the diagonal of the said effective electrode area | region make is 40 degrees or more and 50 degrees or less is mentioned.

The pressure loss in each rectifying unit can be reduced by making the angle between each rectifying unit and the diagonal line of the effective electrode region be 40 ° or more and 50 ° or less.

(9) As one form of the bipolar plate,
It is mentioned that A / S is more than 0.5 and less than 0.95, where S is the area of the facing surface and A is the contact area of the facing surface that contacts the electrode.

Since the ratio A / S of the contact area (A) of the electrode to the area (S) of the opposing surface of the bipolar plate is more than 0.5, the contact area between the electrode and the bipolar plate is secured, and the electrode and the bipolar plate The contact resistance between the plates can be reduced. Thereby, the internal resistance (cell resistance) of the battery can be reduced. In addition, from the viewpoint of ensuring the groove formation area (electrolyte flow path area) on the opposing surface of the bipolar plate, the ratio A / S of the contact area of the electrode is preferably less than 0.95, whereby the electrolyte solution The distribution resistance can be effectively reduced.

(10) The cell frame according to the embodiment is
The bipolar plate according to any one of (1) to (9) above and a frame provided on the outer periphery of the bipolar plate.

Since the cell frame includes the bipolar plate according to the above-described embodiment, the reactivity between the electrode and the electrolytic solution can be improved while reducing the flow resistance of the electrolytic solution. While being able to reduce, it is possible to reduce the reaction resistance at the electrode. Therefore, when the 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.

(11) The cell stack according to the embodiment is
The cell frame according to (10) is provided.

The cell stack includes the cell frame according to the above-described embodiment, so that the reaction resistance at the electrode can be reduced while the pressure loss due to the flow resistance of the electrolytic solution can be reduced. Therefore, when the cell stack is used for a redox flow battery, the internal resistance (cell resistance) of the battery can be reduced, and the battery performance can be improved.

(12) The redox flow battery according to the embodiment is
The cell stack described in (11) above is provided.

Since the redox flow battery includes the cell stack according to the above-described embodiment, it is possible to reduce the reaction loss at the electrode while reducing the pressure loss due to the flow resistance of the electrolytic solution. Resistance (cell resistance) can be reduced. Therefore, the redox flow battery is excellent in battery performance.

[Details of the embodiment of the present invention]
Specific examples of a bipolar plate for a redox flow battery, a cell frame and a cell stack, and a redox flow battery (RF battery) according to an embodiment of the present invention will be described below with reference to the drawings. The same reference numerals in the drawings indicate the same or corresponding parts. In addition, this invention is not limited to these illustrations, is shown by the claim, and it is intended that all the changes within the meaning and range equivalent to a claim are included.

FIG. 4 is a schematic plan view of the cell frame 3 including the bipolar plate 31 according to the embodiment when viewed from the one surface side of the bipolar plate 31. One of the features of the bipolar plate 31 of the embodiment is that it has a tree-like flow path 4 (introduction path 41, discharge path 42) through which the electrolyte flows on the facing surface facing the electrode 14, as shown in FIG. In the point.

In the following, referring to FIG. 1 to FIG. 4, the outline of the RF battery 1 according to the embodiment, and the cell 10 (cell stack 2) and the bipolar plate 31 (cell frame 3) included in the RF battery 1 will be described. explain. Thereafter, the flow path 4 provided in the bipolar plate 31 according to the embodiment will be described in detail mainly with reference to FIGS.

<< RF battery >>
First, an example of the RF battery 1 and the cell 10 (cell stack 2) according to the embodiment will be described with reference to FIGS. The RF battery 1 shown in FIG. 1 and FIG. 2 uses an electrolytic solution containing, as an active material, a metal ion whose valence changes as a result of oxidation and reduction in the positive electrode electrolyte and the negative electrode electrolyte. The battery performs charging / discharging by utilizing the difference between the redox potential and the redox potential of 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 in the positive electrode electrolyte and the negative electrode electrolyte is shown. A solid line arrow in the cell 10 in FIG. 1 indicates a charging reaction, and a broken line arrow indicates a discharging reaction. The RF battery 1 is connected to the electric power system P via an AC / DC converter C, for example, for load leveling applications, applications such as sag compensation and emergency power supplies, natural energy power generation such as solar power generation and wind power generation. Used for output smoothing.

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

"cell"
As shown in FIG. 1, the cell 10 includes a positive electrode 14, a negative electrode 15, and a diaphragm 11 interposed between the electrodes 14 and 15. The structure of the cell 10 is separated into a positive electrode cell 12 and a negative electrode cell 13 with a diaphragm 11 interposed therebetween, and a positive electrode 14 is incorporated in the positive electrode cell 12 and a negative electrode 15 is incorporated in the negative electrode cell 13.

Each electrode of the positive electrode 14 and the negative electrode 15 is formed of a carbon fiber aggregate including carbon fibers. Since the electrode of the carbon fiber aggregate is porous and has voids in the electrode, the electrolytic solution flows through the electrode, and the electrolytic solution can permeate and diffuse. Examples of the carbon fiber aggregate include carbon felt, carbon cloth, and carbon paper. Examples of the carbon fiber include PAN-based carbon fiber using polyacrylonitrile (PAN) fiber as a raw material, pitch-based carbon fiber using pitch fiber as a raw material, and rayon-based carbon fiber using rayon fiber as a raw material. The diaphragm 11 is formed of, for example, an ion exchange membrane that transmits hydrogen ions.

In the cell 10 (the positive electrode cell 12 and the negative electrode cell 13), an electrolytic solution (a positive electrode electrolytic solution and a negative electrode electrolytic solution) circulates through the circulation channels 100P and 100N. A positive electrode electrolyte tank 106 that stores a positive electrode electrolyte is connected to the positive electrode cell 12 via a positive electrode circulation channel 100P. Similarly, a negative electrode electrolyte tank 107 that stores a negative electrode electrolyte is connected to the negative electrode cell 13 via a negative electrode circulation channel 100N. Each circulation flow path 100P, 100N has forward piping 108, 109 for sending the electrolytic solution from each tank 106, 107 to the cell 10 and return piping 110, 111 for returning the electrolytic solution from the cell 10 to each tank 106, 107. Pumps 112 and 113 for pumping the electrolytic solution stored in the tanks 106 and 107 are provided in the outgoing pipes 108 and 109, and the electrolytic solution is circulated to the cell 10 by the pumps 112 and 113.

Cell stack
The cell 10 may be configured as a single cell including a single cell 10 or may be configured as a multi-cell including a plurality of cells 10. The cell 10 is normally used in a form called a cell stack 2 including a plurality of stacked cells 10 as shown in FIG. As shown in the lower diagram of FIG. 3, the cell stack 2 is configured by sandwiching the sub stack 200 from two end plates 220 from both sides and fastening the end plates 220 on both sides by a fastening mechanism 230. FIG. 3 illustrates a cell stack 2 including a plurality of substacks 200. A plurality of sub-stacks 200 are stacked in the order of the cell frame 3, the positive electrode 14, the diaphragm 11, and the negative electrode 15 (see the upper diagram of FIG. 3), and supply / discharge plates 210 (see the lower diagram of FIG. 2 is not shown in FIG. Connected to the supply / discharge plate 210 are the forward pipes 108 and 109 and the return pipes 110 and 111 of the circulation passages 100P and 100N (see FIGS. 1 and 2).

《Cell Frame》
3, the cell 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 FIG. 3). (See also 4). On one surface side of the bipolar plate 31, the positive electrode 14 is disposed so as to face the other surface, and on the other surface side of the bipolar plate 31, the negative electrode 15 is disposed so as to face it. A bipolar plate 31 is provided inside the frame body 32, and a recess 32 o 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 the concave portions 32o with the bipolar plate 31 interposed therebetween. Each recessed part 32o forms each cell space of the positive electrode cell 12 and the negative electrode cell 13 (refer FIG. 1). The planar shape of each of the positive electrode 14 and the negative electrode 15 is not particularly limited, but is rectangular in this embodiment. Moreover, the planar opening shape of the recessed part 32o is the same rectangular shape as an electrode, and the size of the recessed part 32o and an electrode is substantially the same. And the effective electrode area | region where each electrode in the bipolar plate 31 overlaps with a lamination direction is a rectangular shape. In this example, since the positive electrode 14 and the negative electrode 15 have the same size, a region where the bipolar plate 31 and the electrode 14 shown in FIG. 4 face each other is an effective electrode region. When the positive electrode 14 and the negative electrode 15 have different sizes, a region where the three of the positive electrode 14, the negative electrode 15, and the bipolar plate 31 overlap is an effective electrode region.

The bipolar plate 31 is made of, for example, plastic carbon, and the frame body 32 is made of, for example, plastic such as vinyl chloride resin (PVC), polypropylene, polyethylene, fluorine resin, or epoxy resin. In the cell frame 3, a frame 32 is integrated around the bipolar plate 31 by injection molding or the like.

In the cell stack 2 (sub-stack 200), the one surface side and the other surface side of the frame 32 of each adjacent cell frame 3 face each other and face each other, and between the bipolar plates 31 of each adjacent cell frame 3 respectively. One cell 10 is formed. When the cell 10 is assembled, the electrodes 14 and 15 are accommodated in the recessed portions 32o of the frame body 32 in a compressed state in the thickness direction. An annular seal member 37 such as an O-ring or a flat packing is disposed between the frame bodies 32 of each cell frame 3 in order to suppress leakage of the electrolytic solution. A seal groove 38 (see FIG. 4) for arranging the seal member 37 is formed in the frame body 32.

The electrolyte solution in the cell 10 flows through the supply manifolds 33 and 34 and the drainage manifolds 35 and 36 formed through the frame 32 of the cell frame 3 and the supply slits 33 s formed in the frame 32. , 34s and drainage slits 35s, 36s. In the case of the cell frame 3 (frame body 32) shown in this example, the positive electrode electrolyte is supplied from a liquid supply manifold 33 formed in the lower part of the frame body 32 through a liquid supply slit 33s formed on one surface side of the frame body 32. Are supplied to the positive electrode 14 and discharged to the drainage manifold 35 through the drainage slit 35 s formed in the upper part of the frame 32. Similarly, the negative electrode electrolyte is supplied from the liquid supply manifold 34 formed in the lower part of the frame 32 to the negative electrode 15 through the liquid supply slit 34 s formed on the other surface side of the frame 32, and the frame 32. The liquid is discharged to the drainage manifold 36 through the drainage slit 36s formed in the upper part. The liquid supply manifolds 33 and 34 and the drainage manifolds 35 and 36 constitute a flow path for the electrolytic solution by stacking the cell frames 3. These flow paths communicate with the forward pipes 108 and 109 and the return pipes 110 and 111 of the circulation flow paths 100P and 100N (see FIGS. 1 and 2) via the supply / discharge plate 210 (see the lower figure of FIG. 3), respectively. It is possible to distribute the electrolyte in the cell 10.

In the cell 10 shown in this example, the electrolytic solution is introduced from the lower side of the positive electrode 14 and the negative electrode 15, and the electrolytic solution is discharged from the upper side of the electrodes 14, 15. The electrolyte flows from the lower edge of 15 toward the upper edge. 2 and 3, the arrows in the electrodes 14 and 15 indicate the overall flow direction of the electrolytic solution.

《Dipolar plate》
As shown in FIG. 4, a flow path 4 through which an electrolytic solution flows is formed on the opposing surface of the bipolar plate 31 that faces the electrodes 14 and 15. The flow path 4 of this embodiment is comprised by the introduction part 4A, the introduction path 41, the discharge part 4B, and the discharge path 42 which are mentioned later. In FIG. 4, the portion where the flow path 4 is not formed is hatched. One side (the front side of the drawing) of the bipolar plate 31 shown in FIG. 4 is a facing surface facing the positive electrode 14, and the other side (the back side of the drawing) is the negative electrode 15 (see FIG. 3, not shown in FIG. 4). It is the opposing surface which opposes. In the bipolar plate 31 shown in FIG. 4, the lower side to which the liquid supply slit 33s is connected is the positive electrode electrolyte introduction side, and the upper side to which the drainage slit 35s is connected is the positive electrode electrolyte discharge side. In FIG. 4, the thick line arrow on the left side of the drawing indicates the overall flow direction of the electrolytic solution.

In FIG. 4, only one surface side of the bipolar plate 31 facing the positive electrode 14 is shown, but the flow path of the electrolytic solution is also provided on the other surface side of the bipolar plate 31 facing the negative electrode 15, similarly to the one surface side. Is formed. Since the structure of the negative electrode electrolyte channel formed on the other surface side of the bipolar plate 31 is the same as that of the positive electrode electrolyte channel 4 shown in FIG.

<Introduction>
The introduction part 4 </ b> A is a part for introducing the electrolytic solution into the bipolar plate 31. 4 A of introduction parts of this example are provided with the inlet 4i of electrolyte solution, and the introduction side rectification | straightening part 410 formed along the edge of the bipolar plate 31 from the inlet 4i. The inlet 4i is a portion to which the liquid supply slit 33s is connected, and the electrolytic solution is introduced from the inlet 4i through the liquid supply slit 33s. In the present embodiment, the inlet 4i is located at the center of the lower side of the effective electrode region. On the other hand, the introduction side rectification unit 410 is formed along the lower edge of the bipolar plate 31. The introduction path 41 is connected to the introduction side rectification unit 410 and communicates with the inlet 4 i through the introduction side rectification unit 410. The introduction-side rectification unit 410 diffuses the electrolyte introduced from the inlet 4 i along the lower edge of the bipolar plate 31 and uniformly introduces the electrolyte into each introduction path 41. The introduction side rectification unit 410 may be omitted, and in this case, the introduction unit 4A is configured only by the inlet 4i.

<Discharge unit>
The discharge part 4 </ b> B is a part for discharging the electrolytic solution from the bipolar plate 31. The discharge unit 4B of the present example includes an outlet 4o for the electrolyte, and a discharge-side rectifying unit 420 formed along the edge of the bipolar plate 31 from the outlet 4o. The outlet 4o is a portion to which the drainage slit 35s is connected, and the electrolytic solution is discharged from the outlet 4o to the drainage slit 35s. In the present embodiment, the outlet 4o is located at the center of the upper side of the effective electrode region. On the other hand, the discharge side rectification unit 420 is formed along the upper edge of the bipolar plate 31. The discharge path 42 formed in a tree shape is connected to the discharge side rectification unit 420 and communicates with the outlet 4o via the discharge side rectification unit 420. The discharge side rectification unit 420 collects the electrolyte discharged from each discharge path 42 along the upper edge of the bipolar plate 31 at the outlet 4o. The discharge side rectification unit 420 may be omitted, and in that case, the discharge unit 4B is configured only by the outlet 4o.

<Introduction route / Discharge route>
The introduction path 41 includes a plurality of introduction grooves 51 a, 51 b, 51 c connected to the introduction part 4 </ b> A, and diffuses the electrolytic solution from the introduction part 4 </ b> A in the planar direction of the bipolar plate 31. On the other hand, the discharge path 42 is composed of a plurality of discharge grooves 52a, 52b, 52c connected to the discharge part 4B, collects the electrolyte solution diffused in the plane direction of the bipolar plate 31, and guides it to the discharge part 4B. The introduction path 41 and the discharge path 42 are independent without communicating with each other. When the bipolar plate 31 includes the introduction path 41 and the discharge path 42, the electrolytic solution flows so as to cross between the introduction path 41 and the discharge path 42, and at that time, the electrolytic solution permeates and diffuses into the electrode 14. Thus, the electrolytic solution can be uniformly distributed throughout the electrode 14. As a result, the distribution of the electrolytic solution in the electrode 14 can be made more effective and uniform, and the reactivity between the electrode 14 and the electrolytic solution can be further improved.

The flow path 4 shown in FIG. 4 is axisymmetric (left-right symmetric) with a center line (indicated by a one-dot chain line in the figure) connecting the inlet 4i and the outlet 4o as an axis of symmetry, and further, the inlet 4i side ( The lower side is asymmetric with the outlet 4o side (upper side). Since the flow path 4 is formed asymmetrically between the introduction side and the discharge side, it is possible to improve the flow of the electrolyte solution on the discharge side where the pressure of the electrolyte solution decreases.

(groove)
The introduction grooves 51a to 51c constituting the introduction path 41 are connected to the introduction side rectification unit 410, extend from the introduction side (lower side) to the discharge side (upper side), and the distal end on the discharge side is a closed end. . The discharge grooves 52a to 52c constituting the discharge path 42 are connected to the discharge side rectification unit 420, extend from the discharge side (upper side) toward the introduction side (lower side), and the leading end on the introduction side is a closed end. .

Each groove 5 (introduction grooves 51a to 51c and discharge grooves 52a to 52c) is open on the surface of the bipolar plate 31 facing the electrode 14, and as shown in FIG. It is formed so as to become smaller toward. In the case of the introduction grooves 51a to 51c, the opening width decreases toward the tip side, so that the pressure of the electrolyte increases as it approaches the tip side, and the electrolyte solution easily penetrates into the electrode 14 from the introduction grooves 51a to 51c. . The “opening width” of the groove 5 refers to a groove width orthogonal to the longitudinal direction of the groove 5.

The opening width (groove width) and depth (groove depth) of the groove 5 can be appropriately selected according to the size and thickness of the bipolar plate 31 and are not particularly limited. The groove width is, for example, from 0.2 mm to 10 mm, further from 0.5 mm to 5 mm, and the groove depth is, for example, from 0.1 mm to 3 mm, further from 0.2 mm to 2 mm.

As a method for forming the groove 5, for example, the surface of the bipolar plate 31 is cut with a cutting tool such as an end mill. Alternatively, it is also possible to provide a projection corresponding to the shape of the groove 5 in the mold for forming the bipolar plate 31 and form the groove 5 by mold forming such as injection molding.

<Percentage of electrode contact area>
The area of the surface of the bipolar plate 31 facing the electrode 14 (ie, the effective electrode region) is S, and the contact area of the facing surface that is in contact with the electrode 14 (the area of the hatched portion of the bipolar plate 31 shown in FIG. 4) is A. , A / S is preferably more than 0.5 and less than 0.95. Since the ratio A / S of the contact area (A) of the electrode 14 to the area (S) of the opposite surface of the bipolar plate 31 is more than 0.5, the contact area between the electrode 14 and the bipolar plate 31 is secured. The contact resistance between the electrode 14 and the bipolar plate 31 can be reduced. Thereby, the internal resistance (cell resistance) of the battery can be reduced. Further, from the viewpoint of securing the formation area of the grooves 5 (electrolyte flow passage area) on the opposing surface of the bipolar plate 31, the ratio A / S of the contact area of the electrode 14 is preferably less than 0.95. Thus, the flow resistance of the electrolytic solution can be effectively reduced. The ratio A / S of the contact area of the electrode 14 is, for example, preferably 0.6 or more and 0.9 or less, and more preferably 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 on the facing surface when the bipolar plate 31 is viewed in plan.

<Cross-sectional shape>
FIG. 6 shows a cross-sectional shape of the groove 5 in the present embodiment. In the present embodiment, as shown in FIG. 6, the width of the groove 5 on the opening 56 side is equal to or larger than the width on the bottom 57 side in the cross section orthogonal to the flow direction of the electrolyte in the groove 5. The cross-sectional shape is tapered from the opening 56 side toward the bottom 57 side. Therefore, when the width of the groove 5 on the opening 56 side is equal to or larger than the width on the bottom 57 side, the groove 5 can be formed more easily than the case where the width on the bottom 57 side is wider than the opening 56 side. Further, when the cross-sectional shape of the groove 5 (particularly, the introduction grooves 51a to 51c) is tapered from the opening 56 side toward the bottom 57 side, the electrolytic solution can easily penetrate from the groove 5 into the electrode. Examples of the cross-sectional shape of the groove 5 include a rectangular shape, a triangular shape (V shape), a trapezoidal shape, a semicircular shape, and a semielliptical shape.

<Dendritic groove>
Among the grooves 5 shown in FIG. 4, at least a part of the introduction groove and at least a part of the discharge groove are formed in a tree shape.

The dendritic introduction groove is an introduction groove that satisfies the following three conditions. In this example, the introduction grooves 51a and 51c correspond to the dendritic introduction grooves.
· Groove CI ₀ to be connected to inlet portion 4A, and (the n 1 or more natural number) grooves _CI n branching from the groove portion CI ₀ has, not connected to the discharge unit 4B none of the grooves.
· Groove CI _n has branches in a direction intersecting the groove _{CI n-1} in the groove _{CI n-1} in the stretching direction.
When the bipolar plate 31 is viewed in plan, the tip width of any groove is narrower than the width of other portions.
Hereinafter, the groove portion CI _{0 is referred} to as a trunk groove portion 60, the groove portion CI _{1 is referred} to as a branch groove portion 61, and the groove portion CI _{2 is referred} to as a branch groove portion 62. Here, the number of branching of the branch groove, that is, n is preferably 3 or less. By limiting n to 3 or less, excessive narrowing of the groove width of the branch groove portion due to branching can be avoided.

On the other hand, the tree-shaped discharge groove is a discharge groove that satisfies the following three conditions, and in this example, the discharge grooves 52a and 52c correspond to the tree-shaped discharge grooves.
The tree-shaped discharge groove has a groove portion CO ₀ connected to the discharge portion 4B and a groove portion CO _m branched from the groove portion CO ₀ (m is a natural number of 1 or more), and any groove portion is connected to the introduction portion 4A. do not do.
· Groove CO _m has branches in a direction intersecting the groove _{CO m-1} in the extending direction of the groove _{CO m-1.}
When the bipolar plate 31 is viewed in plan, the tip width of any groove is narrower than the width of other portions.
Hereinafter, the groove CO _{0 is referred} to as a trunk groove 70, the groove CO _{1 is referred} to as a branch groove 71, and the groove CO _{2 is referred} to as a branch groove 72. Here, the number of branching of the branch groove portion, that is, m is preferably 3 or less. By limiting m to 3 or less, excessive narrowing of the groove width of the branch groove portion due to branching can be avoided.

As described above, at least a part of the introduction grooves 51a and 51c and at least a part of the discharge grooves 52a and 52c are formed in a tree shape, so that the electrolyte can easily permeate and diffuse over a wide range in the electrode 14. It is possible to make the distribution of the electrolytic solution in the electrode 14 more uniform. Therefore, the reactivity between the electrode 14 and the electrolytic solution can be further improved.

Referring to FIG. 5, the configuration of the introduction groove and the discharge groove formed in a tree shape will be described in detail by taking the introduction groove 51c and the discharge groove 52c as examples.

As shown in FIG. 5, the introduction groove 51 c includes a trunk groove part 60, two branch groove parts 61 branched from the trunk groove part 60, and a branch groove part 62 branched from one branch groove part 61. At the location where the branch groove portion 61 branches from the trunk groove portion 60, the opening width (W _a1 ) of the branch groove portion 61 is smaller than the opening width (W _a0 ) of the trunk groove portion 60. Further, at the location 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. The relationship between the opening widths before and after branching is the same even when the number of branches is further increased, and the opening widths of the groove portions 60, 61, and 62 are gradually reduced as they branch. Therefore, the total area of the trunk groove part 60> the total area of the two branch groove parts 61> the total area of the branch groove part 62. With such a configuration, the contact area between the electrode 14 and the bipolar plate 31 is increased, and the contact resistance between the electrode 14 and the bipolar plate 31 can be reduced.

On the other hand, the discharge groove 52 c includes a trunk groove part 70 and a branch groove part 71 branched from the trunk groove part 70. At the location where the branch groove portion 71 branches from the trunk groove portion 70, the opening width (W _c1 ) of the branch groove portion 71 is smaller than the opening width (W _c0 ) of the trunk groove portion 70. The relationship between the opening widths before and after branching is the same even if the number of branches is further increased, and the opening widths of the groove portions 70 and 71 are gradually reduced as the branching is performed. Therefore, the total area of the trunk groove part 70> the total area of the branch groove part 71. With such a configuration, the contact area between the electrode 14 and the bipolar plate 31 is increased, and the contact resistance between the electrode 14 and the bipolar plate 31 can be reduced.

Furthermore, in this embodiment, as shown in FIG. 5, in the tree-like introduction groove 51c (discharge groove 52c), the branch groove part 61 (71) intersects the trunk groove part 60 (70) non-orthogonally. . Since the branch groove portion 61 (71) intersects the trunk groove portion 60 (70) in a non-orthogonal direction, the flow resistance of the electrolytic solution is larger than when the branch groove portion 61 (71) is perpendicular to the trunk groove portion 60 (70). Can be reduced. “Intersecting non-orthogonally” typically refers to a case where the inclination angle α (β) of the branch groove portion 61 (71) in the extending direction with respect to the extending direction of the trunk groove portion 60 (70) is an acute angle. The inclination angle α (β) is, for example, not less than 10 ° and not more than 80 °.

<Counter comb region>
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 have opposing comb tooth regions that are alternately arranged facing each other. Further, 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 72 of the discharge groove 52a are alternately arranged facing each other, and these also form an opposing comb tooth region. Has been. Since the flow path 4 has the opposing comb tooth region, the amount of the electrolyte flowing so as to cross between the introduction path 41 (introduction grooves 51a to 51c) and the discharge path 42 (discharge grooves 52a to 52c) increases. The electrolyte solution that permeates and diffuses into the electrode 14 increases. Thereby, the reaction efficiency of the electrode 14 and electrolyte solution can be improved.

<Convex>
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 portion may be formed in the wide portion. Since the convex portion 59 is provided in the wide portion of the groove 5, it is possible to suppress the electrode 14 from being buried in the groove 5. In the present embodiment, as shown in FIG. 4, the base end sides (sides connected to the rectifying units 410 and 420) of the introduction groove 51a and the discharge groove 52a are partially widened, and the portion Convex part 59 is provided in this. The shape of the convex portion 59 when viewed in plan is not particularly limited, and various shapes such as a polygonal shape such as a triangle and a quadrangle, a circular shape, and an elliptical shape can be employed. Further, the number of the convex portions 59 arranged in the wide portion may be one or plural.

<Others>
All the groove portions 60, 61, 62, 70, 71, 72 constituting the introduction grooves 51a to 51c and the discharge grooves 52a to 52c may be non-linear and the groove width may be changed randomly. This indicates that the introduction grooves 51a to 51c and the discharge grooves 52a to 52c are formed in a more organic dendritic shape. Such organic dendritic introduction grooves 51a to 51c and discharge grooves 52a to 52c facilitate uniform dispersion of the electrolyte over the entire surface of the electrode 14.

[Effect of the embodiment]
As shown in the embodiment, by providing tree- like introduction grooves 51 a and 51 c and discharge grooves 52 a and 52 c that are independent from each other on the opposing surface of the bipolar plate 31, the electrolyte solution can be quickly supplied in the planar direction of the bipolar plate 31. Can be dispersed. As a result, the flow resistance of the electrolytic solution can be reduced, and the electrolytic solution can be easily distributed uniformly throughout the electrode 14. In particular, since the groove widths of the trunk groove portion 60 and the branch groove portions 61 and 62 of the introduction grooves 51a and 51c become smaller toward the distal end side, the pressure of the electrolytic solution becomes higher as approaching the distal end side. It is easy to permeate and diffuse the electrolytic solution from 61 and 62 into the electrode 14. Further, since the groove widths of the trunk groove portion 70 and the branch groove portions 71 and 72 of the discharge grooves 52a and 52c are reduced toward the distal end side, the electrolyte solution moves too much from the electrode 14 to the discharge grooves 52a and 52c. The amount of the electrolytic solution discharged to the discharge grooves 52a and 52c without reacting with the electrode 14 can be reduced. Thus, according to the bipolar plate 31 of the embodiment, the electrolyte solution can be uniformly distributed on the electrode 14 and the reactivity between the electrode 14 and the electrolyte solution can be improved, so that the internal resistance of the redox flow battery ( (Cell resistance) can be reduced.

Since the cell frame 3 according to the embodiment includes the bipolar plate 31, the reactivity between the electrode 14 and the electrolytic solution can be improved while reducing the flow resistance of the electrolytic solution. The reaction resistance at the electrode 14 can be reduced.

Since the cell stack 2 according to the embodiment includes the cell frame 3, it is possible to reduce the reaction resistance at the electrode 14 while reducing the pressure loss due to the flow resistance of the electrolytic solution.

Since the RF battery 1 according to the embodiment includes the cell stack 2, the reaction resistance at the electrode 14 can be reduced while the pressure loss due to the flow resistance of the electrolytic solution can be reduced. Resistance (cell resistance) can be reduced.

[Modification]
A modification of the bipolar plate 31 will be described with reference to FIG. The bipolar plate 31 shown in FIG. 7 is different from the bipolar plate 31 of the embodiment shown in FIG. Below, it demonstrates centering on difference with embodiment mentioned above.

The effective electrode area of the bipolar plate 31 shown in FIG. 7 is rectangular. In the modification, as shown in FIG. 7, the inlet 4i is positioned at the lower right corner of the effective electrode region, the outlet 4o is positioned at the upper left corner of the effective electrode region, and the inlet 4i and the outlet 4o are the effective electrodes. It is provided at a diagonal position of the region. Further, in the modification, the introduction side rectification unit connected to the inlet 4i is formed along the introduction side rectification unit 410 formed along the lower edge portion of the bipolar plate 31 and the right edge portion of the bipolar plate 31. And an introduction side rectification unit 411. Further, as a discharge side rectification unit connected to the outlet 4o, a discharge side rectification unit 420 formed along the upper edge of the bipolar plate 31, and a discharge side rectification formed along the left edge of the bipolar plate 31 Part 421. The introduction side rectification units 410 and 411 and the discharge side rectification units 420 and 421 are formed so as not to communicate with each other.

7 includes an introduction path 41 and a discharge path 42. The introduction path 41 includes introduction grooves 51a to 51d connected to the introduction side rectification sections 410 and 411, and the discharge path 42 includes discharge grooves 52a to 52d connected to the discharge side rectification sections 420 and 421. Among these grooves, the introduction grooves 51c and 51d (discharge grooves 52c) are dendritic grooves formed in a tree shape, and the trunk groove portion 60 (70) and the branch groove portion 61 branched from the trunk groove portion 60 (70). (71). In the introduction grooves 51c and 51d (discharge groove 52c), the branch groove part 61 (71) intersects the trunk groove part 60 (70) non-orthogonally.

The flow path 4 is axisymmetric with respect to a diagonal line (indicated by a one-dot chain line in the figure) connecting the inlet 4i and the outlet 4o. Further, the angle formed by the rectifying units 410, 411, 420, and 421 and the diagonal line of 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 between each rectifying unit 410, 411, 420, 421 and the diagonal line of the effective electrode region within the above range, pressure loss in the rectifying units 410, 411, 420, 421 can be reduced.

7 has an intermediate groove 54 that is not connected to the introduction path 41 and the discharge path 42, as shown in FIG. The intermediate groove 54 is an independent closed groove that does not communicate with the introduction- side rectification units 410 and 411 and the discharge- side rectification units 420 and 421, and the introduction grooves 51a to 51d and the discharge grooves 52a to 52d.

The intermediate groove 54 is a dendritic groove that satisfies the following three conditions.
· Groove CC ₀ to be connected to the inlet section 4A, and the groove _CC k branching from the groove section CC ₀ (k is a natural number of 1 or more) having a.
· Groove CC _k has branches in a direction intersecting the groove _{CC k-1} in the extending direction of the groove _{CC k-1.}
When the bipolar plate 31 is viewed in plan, the tip width of any groove is narrower than the width of other portions.
Hereinafter, the groove portion CC _{0 is referred} to as a trunk groove portion 80, the groove portion CC _{1 is referred} to as a branch groove portion 81, and the groove portion CC _{2 is referred} to as a branch groove portion 82. Here, it is preferable that the number of branches of the branch groove portion, that is, k is 3 or less. By limiting k to 3 or less, excessive narrowing of the groove width of the branch groove portion due to branching can be avoided.

The trunk groove 80 of the intermediate groove 44 extends along a diagonal line connecting the inlet 4i and the outlet 4o. The branch groove portion 81 is branched from each end portion on the introduction side (lower right side) and the discharge side (upper left side) of the trunk groove portion 80. Furthermore, the branch groove part 82 branches off from the tip of each branch groove part 81. In the intermediate groove 54, the branch groove portion 81 intersects the trunk groove portion 80 in a non-orthogonal manner.

In the flow path 4 shown in FIG. 7, in addition to the opposing comb tooth region formed by the introduction grooves 51c and 51d and the discharge grooves 52c and 52d, the opposed comb tooth region formed by the introduction grooves 51a to 51c or the discharge grooves 52a to 52c and the intermediate groove 54. Have By forming these opposed comb-tooth regions, it is easy to diffuse the electrolytic solution over a wide range with respect to the electrode, and it is easy to make the distribution of the electrolytic solution in the electrode more uniform.

Furthermore, in the modification, the introduction groove 51a and the trunk groove part 60 of the intermediate groove 54 each have a wide part, and the convex part 59 is arranged in each wide part.

[Test Example 1]
A bipolar plate having an electrolyte flow path corresponding to the embodiment was fabricated, and an RF battery was assembled using the bipolar plate, and the cell resistivity was examined.

In Test Example 1, sample No. 1 in which the flow path shown in FIGS. 1-No. Three grooved bipolar plates were prepared. The material of the bipolar plate is plastic carbon. Sample No. 1-No. The bipolar plate No. 3 has the same shape and size, and only the flow path is different, and the electrode contact area A on the surface facing the electrode and the planar opening area B of the grooves constituting the flow path are different. The area (S) of the opposing surface of each bipolar plate is the same at 891 mm ² (27 mm × 33 mm). Table 1 shows the electrode contact area A of the bipolar plate in each sample and the ratio A / S of the electrode contact area (A) to the area (S) of the facing surface.

Sample No. 1-No. A single cell RF battery was assembled using 3 bipolar plates. The single cell was prepared by placing positive and negative electrodes on both sides of the diaphragm and sandwiching the cell frame with bipolar plates from both sides. Carbon felt was used for each positive and negative electrode.

(Measurement of cell resistivity)
A single cell RF battery using the bipolar plate of each sample was subjected to a charge / discharge test under the following test conditions. And the cell resistivity (ohm * cm < ² >) at the time of 3 cycles charging / discharging was calculated | required. Table 1 shows the cell resistivity of each sample. The cell resistivity was calculated by 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 outflow
Charging / discharging method: constant current Current density: 70 (mA / cm ² )
Charging end voltage: 1.55 (V)
Discharge end voltage: 1.00 (V)
Temperature: 25 ° C
<Cell resistivity>
Formula: R = (V2-V1) / 2I
R: Cell resistivity (Ω · cm ² )
I: Current density (A / cm ² )
V1: Voltage (V) at the middle of the charging time
V2: Voltage (V) at the intermediate point of the discharge time

As shown in Table 1, sample no. 1-No. The cell resistivity of No. 3 1> No. 2> No. No. 3 in order, sample No. 2, No. 3 is sample No. Compared with 1, the cell resistivity can be greatly reduced. From this result, it is understood that the ratio (A / S) of the electrode contact area is preferably more than 0.5.

1 Redox flow battery (RF battery)
2 cell stack 10 cell 11 diaphragm 12 positive electrode cell 13 negative electrode cell 14 positive electrode 15 negative electrode 3 cell frame 31 bipolar plate 32 frame 32o recess 33, 34 liquid supply manifold 35, 36 drainage manifold 33s, 34s liquid supply slit 35s, 36s Drain slit 37 Seal member 38 Seal groove 4 Flow path 4A Introducing section 4B Discharging section 4i Inlet 4o Outlet 41 Introducing path 42 Discharging path 5 Grooves 51a, 51b, 51c, 51d Introducing grooves 52a, 52b, 52c, 52d Discharging groove 410 411 Inlet side rectifying portion 420, 421 Discharge side rectifying portion 54 Intermediate groove 56 Opening portion 57 Bottom portion 59 Protruding portion 60 Trunk portion (groove portion CI ₀ )
61 Branch groove part (groove part CI ₁ )
62 Branch groove part (groove part CI ₂ )
70 Trunk groove (groove CO ₀ )
71 Branch groove part (groove part CO ₁ )
72 Branch groove part (groove part CO ₂ )
80 Trunk groove (groove CC ₀ )
81 Branch groove part (groove part CC ₁ )
82 Branch groove (groove CC ₂ )
100P Cathode circulation channel 100N Cathode circulation channel 106 Cathode electrolyte tank 107 Cathode electrolyte tank 108, 109 Outward piping 110, 111 Return piping 112, 113 Pump 200 Substack 210 Supply / discharge plate 220 End plate 230 Tightening mechanism C AC / DC converter P Power system

Claims (12)

1. A bipolar plate having a facing surface facing an electrode of a redox flow battery, and an introduction portion and a discharging portion for an electrolyte solution disposed on the facing surface,
   A groove portion CI _n branching from the groove portion CI _0, and the groove CI ₀ to be connected to the inlet portion, and the introduction groove not connect any of the grooves in the discharge portion,
   A groove portion CO ₀ connected to the discharge portion, and a groove portion CO _m branched from the groove portion CO ₀ , each of the groove portions including a discharge groove not connected to the introduction portion,
   Groove CI _n branches in a direction crossing the extending direction of the groove _{CI n-1} from the groove _{CI n-1,}
   Groove CO _m branches in a direction crossing the extending direction of the groove _{CO m-1} from the groove _{CO m-1,}
   A bipolar plate having a tapered tip at any groove when the bipolar plate is viewed in plan.
   However, n and m are 1 or more arbitrary natural numbers.
2. 2. The bipolar plate according to claim 1, wherein the bipolar plate has an opposing comb tooth region in which a part of the introduction groove and a part of the discharge groove are engaged with each other.
3. An intermediate groove not connected to any of the introduction part, the discharge part, the introduction groove, and the discharge groove;
   The intermediate groove has a groove part CC ₀ extending from the introduction part side toward the discharge part side, and a groove part CC _k branched from the groove part CC ₀ ,
   Groove CC _k branches in a direction crossing the extending direction of the groove _{CC k-1} from the groove _{CC k-1,}
   3. The bipolar plate according to claim 1, wherein when the bipolar plate is viewed in plan, the tip width of any groove is narrower than the width of the other portion.
   However, k is an arbitrary natural number of 1 or more.
4. Having a counter comb tooth region in which a part of the groove part of the introduction groove and a part of the groove part of the intermediate groove mesh with each other;
   The bipolar plate according to claim 3, wherein the bipolar plate has an opposing comb tooth region in which a part of the groove of the discharge groove and a part of the groove of the intermediate groove are engaged with each other.
5. The bipolar plate according to any one of claims 1 to 4, wherein all the groove portions are non-linear, and the groove width changes randomly.
6. The total area of the groove CI _n when bipolar plate in a plan view, the groove CI less than the total area of the _n-1, and the total area of the groove CO _m in a plan view the bipolar plate groove CO _m- bipolar plate according to any one of claims 5 smaller claims 1 than the total area of _1.
7. The introduction part includes an inlet of the electrolyte solution in the bipolar plate, and an introduction side rectification part formed along the edge of the bipolar plate from the inlet,
   The said discharge part is provided with the exit of the said electrolyte solution in the said bipolar plate, and the discharge side rectification | straightening part formed along the edge of the said bipolar plate from the said exit. The bipolar plate according to item.
8. Of the opposed surfaces, the effective electrode region that actually faces the electrode is rectangular,
   The inlet and the outlet are provided at diagonal positions of the effective electrode region;
   The bipolar plate according to claim 7, wherein an angle formed by the introduction-side rectification unit and the discharge-side rectification unit and a diagonal line of the effective electrode region is 40 ° or more and 50 ° or less.
9. 9. The A / S is more than 0.5 and less than 0.95, where S is the area of the facing surface and A is the contact area of the facing surface that contacts the electrode. 2. The bipolar plate according to item 1.
10. A cell frame comprising: the bipolar plate according to any one of claims 1 to 9; and a frame provided on an outer periphery of the bipolar plate.
11. A cell stack comprising the cell frame according to claim 10.
12. A redox flow battery comprising the cell stack according to claim 11.

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