JP2020129501A - Bipolar plate, cell frame, cell stack, and redox flow battery - Google Patents

Abstract

To provide a bipolar plate capable of improving battery reaction efficiency.SOLUTION: A bipolar plate 31 having a supply-side first edge portion 311 to which an electrolytic solution is supplied, and a discharge-side second edge portion 312 from which the electrolytic solution is discharged, includes a first tunnel 51 and a second tunnel 52 that are adjacent to each other, the first tunnel is formed inside the bipolar plate, has an opening at the first edge portion, has a first flow blocking structure at an end portion on the discharge side, and has a first opening portion 61 which is opened to a surface on the electrode side, and the second tunnel is formed inside the bipolar plate, has an opening portion at the second edge portion, has a second flow-blocking structure at an end portion on the supply side, and has a second opening portion 62 opened to a surface on the electrode side.SELECTED DRAWING: Figure 5

Description

The present disclosure relates to bipolar plates, cell frames, cell stacks, and redox flow batteries.

As one of large-capacity storage batteries, a redox flow battery (hereinafter sometimes referred to as "RF battery") is known (see Patent Documents 1 to 3). The RF battery mainly includes a battery cell including a positive electrode, a negative electrode, and a diaphragm interposed between the electrodes. Generally, in an RF battery, a laminated body including a plurality of battery cells called a cell stack is used. The cell stack has a structure in which a cell frame, a positive electrode, a diaphragm, and a negative electrode are repeatedly stacked in order. The cell frame has a bipolar plate arranged between the positive electrode and the negative electrode, and a frame body provided on the outer periphery of the bipolar plate. In the cell stack, positive and negative electrodes are arranged so as to face each other with a diaphragm interposed between bipolar plates of adjacent cell frames to form one battery cell. An electrolytic solution is supplied to the battery cells, a battery reaction occurs at the electrodes, and the reacted electrolytic solution is discharged from the battery cells.

Patent Documents 1 to 3 disclose a bipolar plate having a flow path formed of a plurality of grooves through which an electrolytic solution flows, on the surface facing the electrode (surface on the electrode side).

JP, 2005-122230, A JP, 2005-122231, A JP-A-2015-138771

Further improvement in battery performance of RF batteries is desired, and efficient battery reaction is required. In particular, it is required to improve the flowability of the electrolytic solution and reduce the pressure loss, and at the same time, to diffuse the electrolytic solution over a wide area of the electrode to cause the cell reaction uniformly in the entire area of the electrode.

Then, this indication makes it one of the objectives to provide the bipolar plate which can improve a battery reaction efficiency. In addition, another object of the present disclosure is to provide a cell frame and a cell stack that can improve battery reaction efficiency. Further, another object of the present disclosure is to provide a redox flow battery having high battery reaction efficiency.

The bipolar plate of the present disclosure is
A bipolar plate arranged facing the electrode, having a supply-side first edge to which an electrolytic solution is supplied and a discharge-side second edge to which the electrolytic solution is discharged,
A first tunnel and a second tunnel that are adjacent to each other are provided,
The first tunnel is formed inside the bipolar plate, has an opening at the first edge, and has an end on the discharge side,
The first tunnel has a first opening opening on the surface of the electrode side,
The discharge side end of the first tunnel has a first flow inhibition structure that inhibits the flow of the electrolytic solution from the first tunnel to the second edge,
The second tunnel is formed inside the bipolar plate, has an opening at the second edge, and has an end on the supply side,
The second tunnel has a second opening opening on the surface of the electrode side,
The end on the supply side of the second tunnel has a second flow obstruction structure that obstructs the flow of the electrolytic solution from the first edge to the second tunnel.

The cell frame of the present disclosure is
A bipolar plate of the present disclosure;
A frame provided on the outer periphery of the bipolar plate.

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

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

The bipolar plate of the present disclosure can improve battery reaction efficiency. In addition, the cell frame and cell stack according to the present disclosure can improve battery reaction efficiency. The redox flow battery of the present disclosure has high battery reaction efficiency.

FIG. 1 is an explanatory diagram showing the operating principle of the redox flow battery according to the embodiment. FIG. 2 is a schematic configuration diagram showing an example of the redox flow battery according to the embodiment. FIG. 3 is a schematic configuration diagram showing an example of a cell stack according to the embodiment. FIG. 4 is a schematic plan view of the cell frame according to the embodiment viewed from one surface side. FIG. 5 is a schematic plan view of the bipolar plate according to the embodiment seen from one surface side. FIG. 6 is a schematic sectional view taken along line VI-VI in FIG. FIG. 7 is a schematic sectional view taken along the line VII-VII of FIG. FIG. 8 is a schematic sectional view taken along the line VIII-VIII in FIG. FIG. 9 is a schematic plan view of the bipolar plate according to Modification 1A as viewed from one surface side. FIG. 10 is a schematic plan view of the bipolar plate according to Modification 1B as viewed from one surface side. FIG. 11 is a schematic plan view of a bipolar plate according to Modification 2 as seen from one surface side. FIG. 12 is a schematic plan view of the bipolar plate according to Modification 3 as seen from one surface side. FIG. 13 is a schematic plan view of the bipolar plate according to Modification 4 as seen from one surface side. FIG. 14A is a schematic plan view of a bipolar plate according to Modification 5 as seen from one surface side. FIG. 14B is a schematic sectional view taken along the line BB of FIG. 14A. FIG. 15 is a schematic plan view of a bipolar plate according to another example of the modification 5, as viewed from one surface side.

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

(1) The bipolar plate according to the embodiment of the present disclosure is
A bipolar plate arranged facing the electrode, having a supply-side first edge to which an electrolytic solution is supplied and a discharge-side second edge to which the electrolytic solution is discharged,
A first tunnel and a second tunnel that are adjacent to each other are provided,
The first tunnel is formed inside the bipolar plate, has an opening at the first edge, and has an end on the discharge side,
The first tunnel has a first opening opening on the surface of the electrode side,
The discharge side end of the first tunnel has a first flow inhibition structure that inhibits the flow of the electrolytic solution from the first tunnel to the second edge,
The second tunnel is formed inside the bipolar plate, has an opening at the second edge, and has an end on the supply side,
The second tunnel has a second opening opening on the surface of the electrode side,
The end on the supply side of the second tunnel has a second flow obstruction structure that obstructs the flow of the electrolytic solution from the first edge to the second tunnel.

The bipolar plate of the present disclosure can improve the flowability of the electrolytic solution in the battery cell by providing the first tunnel and the second tunnel as the flow path of the electrolytic solution. Therefore, the bipolar plate of the present disclosure can reduce the flow resistance of the electrolytic solution and reduce the pressure loss of the electrolytic solution in the battery cell.

Since each of the first tunnel and the second tunnel has an opening, each tunnel can adjust the flow of the electrolytic solution between the supply side and the discharge side of the bipolar plate, and each opening allows an electrode to be formed. It is possible to adjust the flow of the electrolytic solution flowing to the. Specifically, the first tunnel and the second tunnel make it difficult to be influenced by the flow of the electrolytic solution at the electrodes and control the flow of the electrolytic solution flowing from the supply side to the discharge side of the bipolar plate. .. Further, the flow of the electrolytic solution flowing through the electrode from the first tunnel to the second tunnel can be controlled via the first opening and the second opening. Therefore, in the bipolar plate of the present disclosure, it is possible to independently design the flow field of the electrolytic solution in the bipolar plate between the supply side and the discharge side and the flow field of the electrolytic solution flowing from the bipolar plate to the electrode. It is possible.

The first flow blocking structure is provided at the discharge side end of the first tunnel, and the second flow blocking structure is provided at the supply side end of the second tunnel. A pressure difference of the electrolyte occurs between the second tunnels. As a result, a flow of the electrolytic solution across the tunnels is generated via the first opening and the second opening, and the electrolytic solution flows to the electrodes. Specifically, the supplied electrolytic solution flows into the first tunnel and flows to the electrode through the first opening. Then, the electrolytic solution that has flowed to the electrode flows out into the second tunnel through the second opening and is discharged. When the electrolytic solution moves between each tunnel and the electrode, the bipolar plate of the present disclosure easily diffuses the electrolytic solution in a wide range of the electrode by passing through each opening. Therefore, the battery reaction can be uniformly generated in the entire area of the electrode, so that the battery reaction can be efficiently performed in the battery cell. Therefore, the bipolar plate of the present disclosure can improve the battery reaction efficiency of the RF battery.

(2) As one form of the bipolar plate,
It can be mentioned that the supply-side and discharge-side ends of the first opening and the supply-side and discharge-side ends of the second opening are closed.

In the above embodiment, the openings on the supply side and the discharge side of each opening are closed, so that each opening does not communicate with the first edge and the second edge. According to the above aspect, the electrolytic solution is more easily diffused in a wide range of the electrode, which contributes to further improvement of the battery reaction efficiency.

(3) As one form of the bipolar plate,
The opening area of the first opening is smaller than the plane cross-sectional area of the first tunnel,
The opening area of the second opening may be smaller than the plane cross-sectional area of the second tunnel.

Since the opening area of each opening is smaller than the plane cross-sectional area of each tunnel, the electrolytic solution can easily flow to the electrode by passing through each opening, and the electrolytic solution can be easily spread to the electrode. Therefore, the above-described embodiment facilitates the diffusion of the electrolytic solution over a wide area of the electrode and contributes to further improvement of the battery reaction efficiency.

(4) As one form of the bipolar plate,
A cross ratio in which the ratio of the width of the first opening to the circumference of the first tunnel and the ratio of the width of the second opening to the circumference of the second tunnel is less than 50%. It has a face.

When the ratio of the width of each opening to the perimeter of each tunnel is less than 50%, the electrolytic solution easily flows through the electrodes and easily spreads over the electrode by passing through each opening. Therefore, the above-described embodiment facilitates the diffusion of the electrolytic solution over a wide area of the electrode and contributes to further improvement of the battery reaction efficiency.

(5) As one form of the bipolar plate,
The distance between the supply-side end of the first opening and the first edge, and the distance between the supply-side end of the second opening and the first edge are substantially Is identical to, and
The distance between the discharge-side end of the first opening and the second edge and the distance between the discharge-side end of the second opening and the second edge are substantially. To be at least one of the above.

In the above-mentioned form, it is easy to uniformly control the flow of the electrolytic solution flowing to the electrodes, and it is easy to cause the battery reaction to be more uniform.

(6) As one form of the bipolar plate,
The first tunnel has a smaller cross-sectional area on the discharge side than on the supply side; and
The second tunnel may have at least one of a larger cross-sectional area on the discharge side than on the supply side.

Since the cross-sectional area of the first tunnel is smaller on the discharge side than on the supply side, the pressure loss of the electrolytic solution in the first tunnel can be reduced. Moreover, since the cross-sectional area of the second tunnel is larger on the discharge side than on the supply side, the pressure loss of the electrolytic solution in the second tunnel can be reduced. Therefore, the said form can reduce more the pressure loss of the electrolyte solution which flows toward a discharge side from a supply side.

(7) As one form of the bipolar plate,
It can be mentioned that the distance between the center line of the first opening and the center line of the second opening is substantially the same in the longitudinal direction.

In the above-mentioned form, it is easy to uniformly control the flow of the electrolytic solution flowing to the electrodes, and it is easy to cause the battery reaction to be more uniform. This is because the flow length of the electrolytic solution flowing from the first opening toward the second opening to the electrode can be made substantially the same.

(8) As one form of the bipolar plate,
The opening area of the first opening and the opening area of the second opening may be substantially the same.

In the above-mentioned form, it is easy to uniformly control the flow of the electrolytic solution flowing to the electrodes, and it is easy to cause the battery reaction to be more uniform. This is because the flow rate of the electrolytic solution flowing into the electrode through the first opening and the flow rate of the electrolytic solution flowing out of the electrode through the second opening can be made substantially the same.

(9) As one mode of the bipolar plate,
The opening area per unit length in the first opening and the second opening may be substantially the same in the longitudinal direction.

In particular, in the case where the first tunnel and the second tunnel each have only one first opening and one second opening, the above embodiment facilitates uniform adjustment of the flow of the electrolytic solution flowing to the electrodes, The battery reaction is likely to occur more uniformly.

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

The cell frame of the present disclosure can diffuse the electrolyte solution over a wide range of the electrode while improving the flowability of the electrolyte solution and reducing the pressure loss. Due to the reduction of the pressure loss and the diffusion of the electrolytic solution, the battery reaction can be uniformly generated in a wide range of the electrode. This is because the cell frame described above has the bipolar plate of the present disclosure described above. Therefore, the cell frame of the present disclosure can improve the battery reaction efficiency of the RF battery.

(11) The cell stack according to the embodiment of the present disclosure is
The cell frame according to (10) above is provided.

Since the cell stack of the present disclosure includes the above-described cell frame of the present disclosure, it is possible to improve the battery reaction efficiency of the RF battery.

(12) The redox flow battery according to the embodiment of the present disclosure is
The cell stack according to (11) above is provided.

The RF battery of the present disclosure includes the cell stack of the present disclosure described above, and thus has high battery reaction efficiency.

[Details of the embodiment of the present disclosure]
Specific examples of the bipolar plate, cell frame, cell stack, and redox flow battery (RF battery) of the present disclosure will be described below with reference to the drawings. The same reference numerals in the drawings indicate the same or corresponding parts. It should be noted that the present invention is not limited to these exemplifications, and is shown by the scope of the claims, and is intended to include meanings equivalent to the scope of the claims and all modifications within the scope.

[Embodiment]
An example of the bipolar plate according to the embodiment is shown in FIGS. As shown in FIG. 5, the bipolar plate 31 according to the embodiment includes a first tunnel 51 and a second tunnel 52 that are adjacent to each other. One of the characteristics of the bipolar plate 31 according to the embodiment is that the first tunnel 51 has a first opening 61 and the second tunnel 52 has a second opening, as shown in FIGS. 5 to 8. It has a part 62. In the following, first, an outline of the RF battery 1 according to the embodiment, the cell stack 2, and the cell frame 3 having the bipolar plate 31 will be described with reference to FIGS. 1 to 4. Then, with reference to Drawing 5-Drawing 13, each composition of the 1st tunnel 51 and the 2nd tunnel 52 with which bipolar plate 31 concerning an embodiment is provided is explained in detail.

<<RF battery>>
An example of the RF battery 1 according to the embodiment and a battery cell 10 included in the RF battery 1 will be described with reference to FIGS. 1 and 2. The RF battery 1 shown in FIGS. 1 and 2 uses, as the positive electrode electrolytic solution and the negative electrode electrolytic solution, an electrolytic solution containing a metal ion whose valence changes by redox as an active material. The RF battery 1 charges and discharges by utilizing the difference between the redox potential of ions contained in the positive electrode electrolyte 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 electrolytic solution containing vanadium (V) ions as a positive electrode electrolytic solution and a negative electrode electrolytic solution is shown. A solid arrow in the battery cell 10 in FIG. 1 indicates a charge reaction, and a broken arrow indicates a discharge reaction. The RF battery 1 is connected to the power system 90 via the AC/DC converter 80. The RF battery 1 is used, for example, for load leveling applications, voltage sag compensation, applications such as emergency power sources, and output smoothing applications for natural energy power generation such as solar power generation and wind power generation. The RF battery 1 may be a manganese-titanium-based RF battery in which the positive electrode electrolyte contains manganese ions and the negative electrode electrolyte contains titanium ions. The electrolyte solution may have a known composition.

The RF battery 1 includes a battery cell 10 that is charged and discharged, tanks 106 and 107 that store an electrolytic solution, and circulation flow paths 100P and 100N that circulate the electrolytic solution between the tank 106 and 107 and the battery cell 10. Prepare

《Battery cell》
As shown in FIG. 1, the battery cell 10 includes a positive electrode 14, a negative electrode 15, and a diaphragm 11 interposed between both electrodes. The structure of the battery cell 10 is divided into a positive electrode cell 12 and a negative electrode cell 13 with a diaphragm 11 interposed therebetween, and the positive electrode cell 12 has a positive electrode 14 and the negative electrode cell 13 has a negative electrode 15 built therein. As shown in FIG. 2, the battery cell 10 is configured by arranging a positive electrode 14 and a negative electrode 15 between bipolar plates 31 so as to face each other with a diaphragm 11 therebetween (see also FIG. 3 ).

(electrode)
An electrolytic solution (a positive electrode electrolytic solution and a negative electrode electrolytic solution) flows through each of the positive electrode 14 and the negative electrode 15. The positive electrode 14 and the negative electrode 15 function as a reaction field where the active material in the electrolytic solution causes a battery reaction. The positive electrode 14 and the negative electrode 15 are formed of a conductive porous body. The diaphragm 11 is formed of, for example, an ion exchange membrane that transmits hydrogen ions.

Each of the positive electrode 14 and the negative electrode 15 preferably contains carbon fiber as a main component (mass ratio of 50% or more), and typically, carbon felt, carbon cloth, carbon paper and the like can be preferably used. .. By using carbon fiber as the main component, the electrode has voids, so that the electrolytic solution can be diffused into the electrode.

The porosity of the electrode is, for example, 50% or more, further 60% or more, 70% or more. When the porosity is 50% or more, the flowability of the electrolytic solution is easily secured and the electrolytic solution is easily diffused sufficiently. The upper limit of the porosity is not particularly limited, but is, for example, 95% or less, and further 90% or less. Here, the porosity in the non-compressed state (natural state) is used. When the true volume of the electrode is V and the apparent volume of the electrode is Va, the porosity can be obtained as {(Va-V)/Va}×100(%). Further, it is preferable that the porosity in the thickness direction of the electrode has a distribution that has a minimum value in the vicinity of the surface on the side of the diaphragm 11. The “vicinity” here means a region within 50 μm in the thickness direction from the surface on the side of the diaphragm 11.

Further, the average thickness of the electrode in the uncompressed state is, for example, 0.1 mm or more and 3 mm or less.

As shown in FIGS. 1 and 2, an electrolytic solution (positive electrode electrolytic solution and negative electrode electrolytic solution) circulates in the battery cells 10 (positive electrode cell 12 and negative electrode cell 13) through circulation channels 100P and 100N. A positive electrode electrolytic solution tank 106 that stores a positive electrode electrolytic solution is connected to the positive electrode cell 12 via a positive electrode circulation flow channel 100P. Similarly, a negative electrode electrolyte tank 107 that stores a negative electrode electrolyte solution is connected to the negative electrode cell 13 via a negative electrode circulation channel 100N. Each circulation flow path 100P, 100N includes a forward path pipe 108, 109 for sending an electrolytic solution from each tank 106, 107 to the battery cell 10, and a return path pipe 110, 111 for returning an electrolytic solution from the battery cell 10 to each tank 106, 107. Have. Pumps 112 and 113 for pumping the electrolytic solution stored in the tanks 106 and 107 are provided in the outward pipes 108 and 109, respectively. The electrolyte is circulated in the battery cell 10 by the pumps 112 and 113.

《Cell stack》
The RF battery 1 normally uses a cell stack 2 in which a plurality of battery cells 10 are stacked as shown in FIG. As shown in FIG. 3, the cell stack 2 is configured by sandwiching a plurality of sub-stacks 200 from both sides thereof with two end plates 220 and tightening the end plates 220 on both sides with a tightening mechanism 230. FIG. 3 illustrates a cell stack 2 including a plurality of sub-stacks 200. The sub-stack 200 has a structure in which the cell frame 3, the positive electrode 14, the diaphragm 11, and the negative electrode 15 are repeatedly stacked in this order, and the supply/discharge plates 210 are arranged at both ends of the stacked body. To the supply/discharge plate 210, the outward pipes 108 and 109 and the return pipes 110 and 111 of the circulation flow passages 100P and 100N (see FIGS. 1 and 2) are connected.

《Cell frame》
As shown in FIG. 3, the cell frame 3 has a bipolar plate 31 arranged 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). ). The positive electrode 14 is arranged on one side of the bipolar plate 31 so as to face it. On the other surface side of the bipolar plate 31, the negative electrode 15 is arranged so as to face it. A bipolar plate 31 is provided inside the frame body 32, and a concave portion 32o is formed by the bipolar plate 31 and the frame body 32. The recesses 32o are formed on both sides of the bipolar plate 31, respectively. The positive electrode 14 is housed in the one recess 32o and the negative electrode 15 is housed in the other recess 32o, so that the positive electrode 14 and the negative electrode 15 are arranged with the bipolar plate 31 interposed therebetween. Each recess 32o forms each cell space of the positive electrode cell 12 and the negative electrode cell 13 (see FIG. 1).

The bipolar plate 31 is formed of, for example, conductive plastic, typically plastic carbon (composite material of conductive carbon and resin). The frame 32 is formed of plastic such as vinyl chloride resin (PVC), polypropylene, polyethylene, fluororesin, or epoxy resin. The cell frame 3 may be manufactured by integrating the frame 32 around the bipolar plate 31 by injection molding or the like. In addition, in the cell frame 3, a sealing member is arranged between the outer peripheral portion of the bipolar plate 31 and the inner peripheral portion of the frame body 32, and the outer peripheral portion of the bipolar plate 31 and the inner peripheral portion of the frame body 32 are overlapped with each other. It can also be manufactured in.

In the cell stack 2 (sub-stack 200), one surface side and the other surface side of the frame bodies 32 of the adjacent cell frames 3 face each other and face each other. One battery cell 10 is formed between the bipolar plates 31 in each adjacent cell frame 3 (see FIG. 3 ). In other words, the bipolar plate 31 is interposed between the adjacent battery cells 10. Each of the positive electrode 14 and the negative electrode 15 is housed in each recess 32o of the frame 32 when the battery cell 10 is constructed. An annular seal member 37 (see FIGS. 2 and 3) such as an O-ring or a flat packing is arranged between the frame bodies 32 of the cell frames 3 in order to suppress leakage of the electrolytic solution. A seal groove 38 (see FIG. 4) for disposing the seal member 37 is formed in the frame body 32.

The flow of the electrolytic solution in the battery cell 10 is carried out by penetrating the frame body 32 of the cell frame 3 with the liquid supply manifolds 33 and 34 and the drainage manifolds 35 and 36, and the liquid supply slit 33s formed in the frame body 32. , 34s and drain slits 35s, 36s. In the case of the cell frame 3 (frame body 32) shown in this example, the positive electrode electrolyte flows from the liquid feed manifold 33 formed in the lower portion of the frame body 32 through the liquid feed slit 33s formed on one surface side of the frame body 32. And is supplied to one side of the bipolar plate 31. The supplied positive electrode electrolytic solution is discharged to the drainage manifold 35 via the drainage slits 35s formed in the upper portion of the frame body 32. Similarly, the negative electrode electrolyte is supplied to the other surface side of the bipolar plate 31 from the liquid supply manifold 34 formed in the lower portion of the frame body 32 through the liquid supply slit 34s formed on the other surface side of the frame body 32. It The supplied negative electrode electrolytic solution is discharged to the drainage manifold 36 through the drainage slit 36s formed in the upper portion of the frame 32. The liquid supply manifolds 33 and 34 and the drainage manifolds 35 and 36 form a flow path of the electrolytic solution by stacking the cell frames 3. These flow passages are connected to the outward pipes 108 and 109 and the return pipes 110 and 111 of the circulation flow passages 100P and 100N (see FIGS. 1 and 2) via the supply/discharge plate 210 (see FIG. 3), respectively. .. As a result, the electrolytic solution can be circulated in the battery cell 10 via the liquid supply manifolds 33 and 34 and the drainage manifolds 35 and 36.

The battery cell 10 shown in this example is configured such that the electrolytic solution is supplied from the lower edge side of the bipolar plate 31 and the electrolytic solution is discharged from the upper edge side of the bipolar plate 31. In other words, the entire flowing direction of the electrolytic solution in the battery cell 10 is the upward direction of the paper surface.

As shown in FIG. 4, the cell frame 3 of the present example has a supply side rectifying section 330 and a discharge side rectifying section 350. The supply side rectifying section 330 is a groove formed on one surface side of the frame body 32 and extending along the lower edge of the inner periphery of the frame body 32. The liquid supply slit 33s is connected to the supply-side rectifying unit 330. The supply side rectification|straightening part 330 has a function which diffuses the positive electrode electrolyte solution supplied from 33 s of liquid supply slits along the lower edge part of the bipolar plate 31. The discharge side rectification section 350 is a groove formed on one surface side of the frame body 32 and extending along the upper edge of the inner circumference of the frame body 32. The drain slit 35s is connected to the discharge side rectifying section 350. The discharge side rectifying section 350 has a function of collecting the positive electrode electrolyte discharged from the upper edge portion of the bipolar plate 31 in the drain slit 35s.

In this example, the supply side rectification section 330 and the discharge side rectification section 350 are provided in the frame 32, but the supply side rectification section 330 and the discharge side rectification section 350 can be provided in the bipolar plate 31. When the supply side rectifying section 330 is provided on the bipolar plate 31, a groove may be formed along the lower edge of the bipolar plate 31. When the discharge side rectifying section 350 is provided on the bipolar plate 31, a groove may be formed along the upper edge of the bipolar plate 31.

In FIG. 4, only the supply side rectifying section 330 and the discharge side rectifying section 350 for the positive electrode electrolyte formed on one surface side (the positive electrode side) of the cell frame 3 in which the positive electrode 14 (see FIG. 3) is arranged are shown. There is. On the other surface side (negative electrode side) of the cell frame 3 on which the negative electrode 15 (see FIG. 3) is arranged, similarly to the one surface side, the supply side rectifying section and the discharge side rectifying section for the negative electrode electrolyte are formed. There is. Since the configurations of the supply side rectification section and the discharge side rectification section for the negative electrode electrolyte formed on the other surface side of the cell frame 3 are similar to those of the supply side rectification section 330 and the discharge side rectification section 350 shown in FIG. The description is omitted.

《Bipolar plate》
As shown in FIGS. 4 and 5, the bipolar plate 31 has a supply-side first edge 311 to which the electrolytic solution is supplied and a discharge-side second edge 312 to which the electrolytic solution is discharged. .. In the case of this example, the lower edge of the bipolar plate 31 is the first edge 311 on the side to which the electrolytic solution is supplied. The upper edge of the bipolar plate 31 is the second edge 312 on the side where the electrolytic solution is discharged.

The planar shape of the bipolar plate 31 of this example is a rectangular shape. One surface side (front side of the paper surface) of the bipolar plate 31 shown in FIGS. 4 and 5 is a surface facing the positive electrode 14 (see FIG. 3 ). The other surface side (back side of the paper surface) of the bipolar plate 31 is a surface facing the negative electrode 15 (see FIG. 3 ).

The bipolar plate 31 includes a first tunnel 51 and a second tunnel 52. Hereinafter, an example of the configurations of the first tunnel 51 and the second tunnel 52 will be described in detail with reference to FIGS. 5 to 8. In the following description, the direction from the supply side (first edge 311) of the bipolar plate 31 toward the discharge side (second edge 312) (vertical direction on the paper surface) is defined as the length direction. The direction along the first edge portion 311 and the second edge portion 312 (the left-right direction on the paper surface) is the width direction. Further, the direction orthogonal to both the length direction and the width direction is the thickness direction. 5 to 8, only the first tunnel 51 and the second tunnel 52 for the positive electrode electrolyte provided on one surface side (positive electrode side) of the bipolar plate 31 are illustrated, but the other surface side of the bipolar plate 31 ( The negative electrode side) is also provided with a first tunnel and a second tunnel for the negative electrode electrolytic solution, similarly to the one surface side. The configurations of the first tunnel and the second tunnel for the negative electrode electrolyte formed on the other surface side of the bipolar plate 31 are the same as those of the first tunnel 51 and the second tunnel 52 shown in FIGS. 5 to 8. Therefore, the description thereof will be omitted.

The first tunnel 51 and the second tunnel 52 are arranged inside the one surface side (positive electrode side) of the bipolar plate 31 so as to be adjacent to each other in the width direction. In the case of this example, as shown in FIG. 5, the first tunnels 51 and the second tunnels 52 are alternately arranged side by side over substantially the entire area on one side of the bipolar plate 31. The first tunnel 51 and the second tunnel 52 do not communicate with each other and are independent. The first tunnel 51 and the second tunnel 52 may be formed in at least a partial region on one surface side of the bipolar plate 31.

(First tunnel)
As shown in FIG. 6, the first tunnel 51 is formed inside the bipolar plate 31 and extends from the supply side (first edge 311) to the discharge side (second edge 312). The first tunnel 51 is open at the first edge 311 and has an end 512 on the discharge side. The end 512 on the discharge side has a first flow blocking structure 512a described later. Further, the first tunnel 51 has a first opening 61 described later, as shown in FIGS. 5 and 6.

The first tunnel 51 is linearly formed. In this example, the cross-sectional shape of the first tunnel 51 is uniform in the longitudinal direction, and the cross-sectional area of the first tunnel 51 is substantially the same in the longitudinal direction. The “cross-sectional shape of the first tunnel 51” is a shape of a cross section orthogonal to the longitudinal direction of the first tunnel 51. The “cross-sectional area of the first tunnel 51” is the cross-sectional area of the cross section of the first tunnel 51. “The cross-sectional area of the first tunnel 51 is substantially the same in the longitudinal direction” means the ratio of the standard deviation (σ) to the average value (ave) of the cross-sectional area of the first tunnel 51 [(σ/ave)× 100] is 30% or less. It can be said that the smaller this ratio is, the more the cross-sectional area of the first tunnel 51 is the same in the longitudinal direction. The above ratio is preferably 20% or less and 10% or less. The average value (ave) and the standard deviation (σ) of the cross-sectional area of the first tunnel 51 are selected at a plurality of arbitrary points (for example, 10 points or more) in the longitudinal direction of the first tunnel 51. The average value and standard deviation shall be determined from the cross-sectional area of. The arbitrary points may be set at equal intervals along the longitudinal direction of the first tunnel 51. In this example, the cross-sectional area of the first tunnel 51 is constant along the longitudinal direction, and the ratio of the standard deviation to the average value of the cross-sectional area of the first tunnel 51 is substantially 0%.

The cross-sectional shape of the first tunnel 51 is rectangular (see FIG. 8). The sectional shape of the first tunnel 51 is not limited to a rectangular shape, and may be, for example, a circular shape, a semicircular shape, an elliptical shape, a semielliptical shape, a triangular shape, a trapezoidal shape, or another polygonal shape. The cross-sectional area of the first tunnel 51 is, for example, 1 mm ² or more and 200 mm ² or less, and further 2 mm ² or more and 50 mm ² or less. When the cross-sectional area of the first tunnel 51 is 1 mm ² or more and 200 mm ² or less, the flowability of the electrolytic solution can be secured.

The length of the first tunnel 51 (the dimension indicated by L ₅₁ in FIG. 6) is, for example, 70% of the length of the bipolar plate 31 (the dimension from the first edge 311 to the second edge 312). As mentioned above, it may be 80% or more and 90% or more. The length of the first tunnel 51 is equal to the distance from the first edge 311 to the end 512 on the discharge side. The width of the first tunnel 51 (the dimension indicated by W ₅₁ in FIG. 8) is, for example, 1 mm or more and 50 mm or less, and further 2 mm or more and 20 mm or less. The width of the first tunnel 51 may change in the thickness direction of the bipolar plate 31. In this case, the width of the first tunnel 51 is the maximum width in the cross section of the first tunnel 51. For example, when the cross-sectional shape of the first tunnel 51 is circular, the width becomes maximum at the center position of the first tunnel 51, and one side (front surface side) and the other side in the thickness direction of the bipolar plate 31 from the center position. The width decreases toward the side (center side). The height of the first tunnel 51 (the dimension indicated by H ₅₁ in FIG. 8) is, for example, 1 mm or more and 20 mm or less, and further 2 mm or more and 10 mm or less. In this example, the width and height of the first tunnel 51 are constant along the longitudinal direction of the first tunnel 51.

<First opening>
As shown in FIG. 6, the first opening 61 opens on the surface of the bipolar plate 31 on the electrode side (the positive electrode 14 side). The first opening 61 is formed on the electrode-side surface of the bipolar plate 31 facing the electrode and communicates with the first tunnel 51. The first opening 61 is formed along the longitudinal direction of the first tunnel 51. In this example, the first opening 61 is formed by one long hole.

The planar shape of the first opening 61 is rectangular (see FIG. 5). The planar shape of the first opening 61 may be, for example, an elliptical shape, a polygonal shape, or the like other than the rectangular shape shown in FIG. Examples of the polygonal shape include a triangular shape, a trapezoidal shape, a rhombic shape, and a hexagonal shape. In the portion of the first tunnel 51 where the first opening 61 is formed, the width of the first opening 61 (the dimension indicated by W ₆₁ in FIG. 8) is equal to the width of the first tunnel 51 (W Less than ₅₁ ). The “width of the first opening 61” is the width at the connecting position between the first tunnel 51 and the first opening 61 in the cross section of the first tunnel 51. The width of the first opening 61 is, for example, 1 mm or more and 50 mm or less, and further 2 mm or more and 20 mm or less. The width of the first opening 61 is preferably smaller than the width of the first tunnel 51. In this example, the width of the first opening 61 is constant along the longitudinal direction of the first tunnel 51 and smaller than the width of the first tunnel 51. Further, when the bipolar plate 31 is viewed in a plan view, the center line of the first opening 61 (shown by a chain double-dashed line in FIG. 5) coincides with the center line of the first tunnel 51. The “center line of the first opening 61 ”is a line passing through the center of the width of the first opening 61 along the longitudinal direction of the first tunnel 51. The “center line of the first tunnel 51” is a line passing through the center of the width of the first tunnel 51 along the longitudinal direction of the first tunnel 51.

In the portion of the first tunnel 51 where the first opening 61 is formed, the ratio of the width (W ₆₁ ) of the first opening 61 to the circumference of the first tunnel 51 is less than 50%. It is preferable. The “perimeter of the first tunnel 51” is the perimeter of the cross section of the first tunnel 51. In the portion of the first tunnel 51 where the first opening 61 is not formed, the periphery of the cross section of the first tunnel 51 is closed. That is, 100% of the circumference of the first tunnel 51 is closed. On the other hand, in the portion of the first tunnel 51 where the first opening 61 is formed, the first opening 61 opens the periphery of the cross section of the first tunnel 51 (see FIG. 8 ). In the cross section of the first tunnel 51, the circumferential length of the portion of the first tunnel 51 where the first opening 61 is formed is equal to the wall length of the first tunnel 51 and the first opening 61. Total with width. “The ratio of the width of the first opening 61 to the perimeter of the first tunnel 51 is less than 50%” means that the width of the first opening 61 with respect to the average value of the perimeter of the first tunnel 51. It means that the ratio of the average value is more than 0% and less than 50%. The average value of the perimeter of the first tunnel 51 and the width of the first opening 61 is a plurality of arbitrary points in the longitudinal direction in the portion of the first tunnel 51 where the first opening 61 is formed ( (For example, 10 points or more) are selected, and the average value of the circumference of the first tunnel 51 and the width of the first opening 61 at each point is selected. The arbitrary points may be set at equal intervals along the longitudinal direction of the first tunnel 51. It can be said that the smaller the above-mentioned ratio is, the larger the ratio that the periphery of the cross section of the first tunnel 51 is closed. If the ratio is less than 50%, more than 50% and less than 100% of the circumference of the first tunnel 51 is closed. The above ratio is preferably less than 40% and less than 30%.

As shown in FIG. 6, the first opening 61 of the present example has a supply side end 611 and a discharge side end 621 closed. Therefore, the first opening 61 does not communicate with the first edge 311 and the second edge 312. Further, as shown in FIG. 5, the opening area of the first opening 61 is smaller than the planar cross-sectional area of the first tunnel 51. The “opening area of the first opening 61” is the area of the first opening 61 when the bipolar plate 31 is viewed in a plan view. The “planar cross-sectional area of the first tunnel 51” is the maximum cross-sectional area of the first tunnel 51 in a cross section parallel to the surface direction of the bipolar plate 31, that is, a cross section orthogonal to the thickness direction. In other words, the plane cross-sectional area of the first tunnel 51 is equal to the area obtained from the contour of the first tunnel 51 when the bipolar plate 31 is seen through. The opening area of the first opening 61 is preferably 50% or less of the plane cross-sectional area of the first tunnel 51, and more preferably 30% or less.

(Second tunnel)
As shown in FIG. 7, the second tunnel 52 is formed inside the bipolar plate 31, and extends from the discharge side (second edge portion 312) toward the supply side (first edge portion 311). The second tunnel 52 opens at the second edge 312 and has an end 521 on the supply side. The supply-side end 521 has a second flow blocking structure 521a described later. In addition, the second tunnel 52 has a second opening 62 that opens to the surface of the bipolar plate 31 on the electrode side (the positive electrode 14 side), as shown in FIGS. 5 and 7.

The difference between the first tunnel 51 and the second tunnel 52 is that the first tunnel 51 opens at the first edge 311 and has an end 512 on the discharge side, whereas the second tunnel 52 It is open to the second edge 312 and has an end 521 on the supply side. In the above description of the first tunnel 51, the terms “first tunnel 51” and “first opening 61” should be read as “second tunnel 52” and “second opening 62”, respectively. , Of the second tunnel 52. The length of the second tunnel 52 (the dimension indicated by L ₅₂ in FIG. 7) is equal to the distance from the second edge 312 to the end 521 on the supply side. Further, W ₅₂ and H ₅₂ in FIG. 8 indicate the width and height of the second tunnel 52. W _{62 in} FIG. 8 indicates the width of the second opening 62. In this example, the width and height of the first tunnel 51 are the same as the width and height of the second tunnel 52, and the cross-sectional area of the first tunnel 51 and the cross-sectional area of the second tunnel 52 are equal. ..

In the case of this example, as shown in FIG. 5, a first tunnel 51 and a second tunnel 52 are provided in parallel. The first tunnel 51 and the second tunnel 52 are provided so as to be partially aligned with each other in the width direction. Specifically, the portion of the first tunnel 51 from the vicinity of the opening to the end portion 512 and the portion of the second tunnel 52 from the vicinity of the opening to the end portion 521 are formed so as to be aligned in the width direction. There is. The first opening 61 and the second opening 62 have the same length and are formed so as to be aligned with each other in the width direction.

<Flow obstruction structure>
The discharge-side end portion 512 of the first tunnel 51 has a first flow blocking structure 512a, as shown in FIG. The end 521 on the supply side of the second tunnel 52 has a second flow obstruction structure 521a as shown in FIG. The first flow blocking structure 512a is a structure that blocks the outflow of the electrolytic solution from the first tunnel 51 to the second edge 312. The second flow blocking structure 521a is a structure that blocks the inflow of the electrolytic solution from the first edge portion 311 to the second tunnel 52. The first flow blocking structure 512a and the second flow blocking structure 521a may each be a structure that blocks the flow of the electrolytic solution. Specific examples of the first flow blocking structure 512a and the second flow blocking structure 521a include a structure in which the discharge-side end 512 and the supply-side end 521 are completely closed or partially closed. The structure which was made is mentioned. The “partially closed structure” means, for example, that the cross-sectional area of the first tunnel 51 or the second tunnel 52 is partially reduced at the end 512 on the discharge side or the end 521 on the supply side. Can be mentioned. In this example, the first flow obstruction structure 512a and the second flow obstruction structure 521a are configured by a structure in which the discharge end 512 and the supply end 521 are completely closed.

Depending on the structure in which the discharge side end 512 of the first tunnel 51 or the supply side end 521 of the second tunnel 52 is partially closed, the first flow blocking structure 512a or the second flow blocking structure 521a. The following requirements shall be satisfied when configuring In the first tunnel 51, the discharge-side end portion 512 provided with the first flow-blocking structure 512a is partially closed and has a small cross-sectional area. The cross-sectional area of the opening of the discharge-side end portion 512 of the first tunnel 51 is smaller than the cross-sectional area of the second edge portion 312 of the adjacent second tunnel 52. In the second tunnel 52, the end portion 521 on the supply side where the second flow obstruction structure 521a is provided is partially closed and has a small cross-sectional area. The cross-sectional area of the opening of the discharge-side end 521 of the second tunnel 52 is smaller than the cross-sectional area of the first edge 311 of the adjacent first tunnel 51.

(Method of manufacturing bipolar plate)
The following method can be given as an example of a method for manufacturing the bipolar plate 31 of this example. The first tunnel 51 is formed by making a hole from the supply side (first edge 311) of the bipolar plate 31 toward the discharge side (second edge 312) with a drill or the like. In the case of this example, since the first flow blocking structure 512a is formed at the discharge-side end portion 512 of the first tunnel 51, the discharge-side end portion 512 is left and the first tunnel 51 is formed. A hole is opened from one surface side (positive electrode side) of the bipolar plate 31 so as to communicate with the first tunnel 51, and a first opening 61 is formed. Further, a hole is drilled from the discharge side (second edge portion 312) of the bipolar plate 31 toward the supply side (first edge portion 311) by a drill or the like to form the second tunnel 52. In the case of this example, since the second flow obstruction structure 521a is formed at the end 521 on the supply side of the second tunnel 52, the second tunnel 52 is formed leaving the end 521 on the supply side. A hole is opened from one surface side (positive electrode side) of the bipolar plate 31 so as to communicate with the second tunnel 52, and a second opening 62 is formed.

As another example of the method for manufacturing the bipolar plate 31, the bipolar plate 31 is divided in the thickness direction, and the bipolar plate 31 is divided into a base portion in which the first tunnel 51 and the second tunnel 52 are formed and a first opening. It may be mentioned that the part 61 and the surface layer part in which the second opening 62 is formed are manufactured separately. In this case, a groove to be the first tunnel 51 and the second tunnel 52 is formed on the surface of the base. Further, holes to be the first opening 61 and the second opening 62 are made in the surface layer. Then, the grooves to be the first tunnel 51 and the second tunnel 52 formed in the base portion and the holes to be the first opening portion 61 and the second opening portion 62 formed in the surface layer portion overlap each other, The surface layer is attached to the base to be integrated. The base portion and the surface layer portion can be integrated by using, for example, heat welding or adhesion with an adhesive.

(Function of bipolar plate)
The bipolar plate 31 of the present example including the first tunnel 51 and the second tunnel 52 has the following functions. The electrolytic solution (positive electrode electrolytic solution) supplied from the supply side (first edge portion 311) mainly flows into the first tunnel 51. The electrolytic solution that has flowed into the first tunnel 51 flows to the electrode (positive electrode 14) through the first opening 61. At this time, the electrolytic solution flows from the first opening 61 toward the second opening 62. That is, the electrolytic solution flows so as to extend between the first tunnel 51 and the second tunnel 52 which are adjacent to each other. Therefore, the electrolytic solution is easily diffused in a wide area of the electrode. The electrolytic solution that has flowed to the electrodes flows into the second tunnel 52 through the second opening 62 and is discharged from the discharge side (second edge portion 312).

In this example, the first tunnel 51 and the second tunnel 52 adjacent to each other satisfy the following conditions (i) to (iv).

(I) The distance between the end 611 on the supply side of the first opening 61 and the first edge 311 (the dimension indicated by D ₆₁₁ in FIG. 6) and the distance on the supply side of the second opening 62. The distance between the end 621 and the first edge 311 (the dimension indicated by D ₆₂₁ in FIG. 7) is substantially the same, and the end 612 on the discharge side of the first opening 61. To the second edge 312 (the dimension indicated by D ₆₁₂ in FIG. 6) and the distance between the discharge-side end 622 of the second opening 62 and the second edge 312 (FIG. 7). And the dimension indicated by D ₆₂₂ ) is substantially the same.

“The distance (D ₆₁₁ ) between the supply-side end 611 of the first opening 61 and the first edge 311 and the supply-side end 621 and the first edge 311 of the second opening 62. Is substantially the same as the distance (D ₆₂₁ ) with respect to". The distance at the end 611 on the supply side (D ₆₁₁ ) and the distance at the end 621 on the supply side (D ₆₂₁ ) are measured. Here, an arbitrary set (for example, 10 sets or more) is selected from a plurality of sets of the first opening 61 and the second opening 62 adjacent to each other. For each of the selected plurality of first openings 61 and second openings 62, the distance (D ₆₁₁ ) between each end 611 and the first edge 311 and each end 621 and first The distance (D ₆₂₁ ) from the edge 311 is measured. Then, the average value (ave) and the standard deviation (σ) of the distance (D ₆₁₁ ) at the end 611 on the supply side and the distance (D ₆₂₁ ) at the end 621 on the supply side are obtained, and the standard with respect to the average value (ave) is obtained. When the ratio [(σ/ave)×100] of the deviation (σ) is 50% or less, it is considered that the distances are substantially the same. It can be said that the smaller the ratio is, the more the distance is the same. The above ratio is preferably 30% or less and 20% or less.

“The distance (D ₆₁₂ ) between the discharge-side end 612 of the first opening 61 and the second edge 312, and the discharge-side end 622 and the second edge 312 of the second opening 62. Is substantially the same as the distance (D ₆₂₂ ) with respect to. The distance at the end 612 on the discharge side (D ₆₁₂ ) and the distance at the end 622 on the discharge side (D ₆₂₂ ) are measured. Here, an arbitrary set (for example, 10 sets or more) is selected from a plurality of sets of the first opening 61 and the second opening 62 adjacent to each other. For each of the plurality of selected first openings 61 and second openings 62, the distance (D ₆₁₂ ) between each end 612 and the second edge 312, and each end 622 and the second opening 312. The distance (D ₆₂₂ ) from the edge 312 is measured. Then, the average value (ave) and the standard deviation (σ) of the distance (D ₆₁₂ ) at the end portion 612 on the discharge side and the distance (D ₆₂₂ ) at the end portion 622 on the discharge side are obtained, and the standard value with respect to the average value (ave) is calculated. When the ratio [(σ/ave)×100] of the deviation (σ) is 50% or less, it is considered that the distances are substantially the same. It can be said that the smaller the ratio is, the more the distance is the same. The above ratio is preferably 30% or less and 20% or less.

In this example, the distance (D ₆₁₁ ) at the end ₆₁₁ on the supply side and the distance (D ₆₁₂ ) at the end 621 on the supply side are equivalent to each other, and the distance (D ₆₁₁ ) and the distance (D ₆₁₂ ) with respect to the average value. The standard deviation percentage is substantially 0%. Further, the distance (D ₆₁₂ ) at the discharge side end ₆₁₂ and the distance (D ₆₂₂ ) at the discharge side end 622 are equal, and the standard deviation of the distance (D ₆₁₂ ) and the average value of the distance (D ₆₂₂ ) from the average value. Is substantially 0%.

The distance at the end 611 on the supply side (D ₆₁₁ ) and the distance at the end 621 on the supply side (D ₆₂₁ ), and the distance at the end 612 on the discharge side (D ₆₁₂ ) and the distance at the end 622 on the discharge side (D). _Since at least one of ₆₂₂ ) is substantially the same, it is easy to uniformly control the flow of the electrolytic solution flowing to the electrodes, and it is easy to cause the battery reaction to be more uniform. In particular, the distance at the end 611 on the supply side (D ₆₁₁ ) and the distance at the end 621 on the supply side (D ₆₂₁ ), and the distance at the end 612 on the discharge side (D ₆₁₂ ) and the distance at end 622 on the discharge side. It is preferable that both of (D ₆₂₂ ) are substantially the same. In this case, it is easy to adjust the flow of the electrolytic solution flowing through the electrodes more uniformly.

(Ii) The distance between the center line of the first opening 61 and the center line of the second opening 62 (the dimension indicated by C ₆ in FIG. 5) is substantially the same in the longitudinal direction.

“The distance (C ₆ ) between the center line of the first opening 61 and the center line of the second opening 62 is substantially the same in the longitudinal direction” means that the first opening 61 and the second opening This means that the ratio [(σ/ave)×100] of the standard deviation (σ) to the average value (ave) of the distance (C ₆ ) from the center line to the portion 62 is 50% or less. It can be said that the smaller the ratio is, the more the distance between the center line of the first opening 61 and the center line of the second opening 62 is the same in the longitudinal direction. The above ratio is preferably 30% or less and 20% or less. For the average value (ave) and standard deviation (σ) of the distance between the center lines of the first opening 61 and the second opening 62, a plurality of arbitrary points (for example, 10 points or more) are selected in the longitudinal direction. Then, the average value and the standard deviation are calculated from the distance between the center lines at each point. Arbitrary points may be set at equal intervals along the longitudinal direction.

In this example, the center line of the first opening 61 and the center line of the second opening 62 are parallel to each other, and the distance between the center lines of the first opening 61 and the second opening 62 ( The ratio of the standard deviation to the average value of C ₆ ) is substantially 0%. The distance (C ₆ ) between the center line of the first opening 61 and the center line of the second opening 62 is, for example, 2 mm or more and 50 mm or less.

The distance (C ₆ ) between the center line of the first opening portion 61 and the center line of the second opening portion 62 is substantially the same in the longitudinal direction, so that the flow of the electrolytic solution flowing through the electrodes is adjusted uniformly. It is easy to cause the battery reaction to occur more uniformly. This is because the flow length of the electrolytic solution flowing from the first opening 61 toward the second opening 62 to the electrode can be made substantially the same.

(Iii) The opening area of the first opening 61 and the opening area of the second opening 62 are substantially the same.

"The opening area of the first opening 61 and the opening area of the second opening 62 are substantially the same" means that the opening area of the first opening 61 and the opening area of the second opening 62 are the same. It means that the difference of each opening area is 30% or less with respect to the average value of. It can be said that the smaller the ratio is, the larger the opening area of the first opening 61 and the opening area of the second opening 62 are. The above ratio is preferably 20% or less and 10% or less.

In this example, the opening area of the first opening 61 and the opening area of the second opening 62 are equal, and the difference between the opening areas of the first opening 61 and the second opening 62 is different from the average value. Is substantially 0%.

Since the opening area of the first opening 61 and the opening area of the second opening 62 are substantially the same, it is easy to uniformly adjust the flow of the electrolytic solution flowing to the electrodes, and to make the battery reaction more uniform. Easy to cause. This is because the flow rate of the electrolytic solution flowing into the electrode through the first opening 61 and the flow rate of the electrolytic solution flowing out of the electrode through the second opening 62 can be made substantially the same.

(Iv) The opening area per unit length in the first opening 61 and the second opening 62 is substantially the same in the longitudinal direction.

"The opening area per unit length is substantially the same in the longitudinal direction" is defined as follows. The opening area per unit length (for example, 1 cm) in the first opening 61 and the second opening 62 is measured. Here, the first opening 61 and the second opening 62 are divided into a plurality of arbitrary sections (for example, 10 or more) in the longitudinal direction, and the opening area per unit length in each section is measured. .. Arbitrary sections may be set at equal intervals along the longitudinal direction. Then, the average value (ave) and the standard deviation (σ) of the opening area per unit length in each section in the first opening portion 61 and the second opening portion 62 are obtained, and the standard deviation with respect to the average value (ave). When the ratio [(σ/ave)×100] of (σ) is 30% or less, the opening areas per unit length are considered to be substantially the same. It can be said that the smaller this ratio is, the more the opening area per unit length is the same. The above ratio is preferably 20% or less and 10% or less.

In this example, the width of each of the first opening 61 and the second opening 62 is constant along the longitudinal direction, and the width of the first opening 61 and the width of the second opening 62 are equal to each other. equal. Therefore, the opening areas per unit length in the first opening 61 and the second opening 62 are equal, and the ratio of the standard deviation to the average value of the opening areas per unit length is substantially 0%. is there.

Since the opening areas per unit length in the first opening 61 and the second opening 62 are substantially the same in the longitudinal direction, it is easy to uniformly adjust the flow of the electrolytic solution flowing to the electrodes, and the battery reaction Is more likely to occur more uniformly.

[Effect of Embodiment]
Since the bipolar plate 31 according to the embodiment includes the first tunnel 51 and the second tunnel 52, the flowability of the electrolytic solution in the battery cell 10 (see FIGS. 2 and 3) can be improved. Therefore, the bipolar plate 31 can reduce the flow resistance of the electrolytic solution and reduce the pressure loss of the electrolytic solution in the battery cell 10.

Further, the first tunnel 51 has a first opening 61, and the second tunnel 52 has a second opening 62. Therefore, the bipolar plate 31 uses the first tunnel 51 and the second tunnel 52 to cause the electrolysis between the supply side (first edge 311) and the discharge side (second edge 312) of the bipolar plate 31. The flow of liquid can be adjusted. Further, the bipolar plate 31 can adjust the flow of the electrolytic solution flowing from the bipolar plate 31 to the electrodes by the first opening 61 and the second opening 62. Therefore, the bipolar plate 31 can independently design the flow field of the electrolytic solution inside the bipolar plate 31 between the supply side and the discharge side and the flow field of the electrolytic solution flowing from the inside of the bipolar plate 31 to the electrode. It is possible.

By arranging the first tunnel 51 and the second tunnel 52 so as to be adjacent to each other, it is easy to diffuse the electrolytic solution over a wide range of the electrode. The first tunnel 51 has the first flow blocking structure 512a at the discharge-side end 512, and the second tunnel 52 has the second flow blocking structure 521a at the supply-side end 521. The electrolytic solution supplied from the side (first edge portion 311) mainly flows into the first tunnel 51. In the first tunnel 51 and the second tunnel 52, a pressure difference of the electrolytic solution is generated by the first flow blocking structure 512a and the second flow blocking structure 521a. Therefore, the electrolytic solution that has flowed into the first tunnel 51 flows into the electrode through the first opening 61. At this time, the electrolytic solution flows from the first opening 61 toward the second opening 62. That is, the flow of the electrolytic solution across the first tunnel 51 and the second tunnel 52 causes the electrolytic solution to easily diffuse in a wide area of the electrode. The electrolytic solution that has flowed to the electrodes flows into the second tunnel 52 through the second opening 62 and is discharged from the discharge side (second edge portion 312). Therefore, the bipolar plate 31 can uniformly cause the battery reaction in the entire area of the electrode, and can efficiently perform the battery reaction in the battery cell 10. Therefore, the bipolar plate 31 can improve the battery reaction efficiency of the RF battery 1.

Since the cell frame 3 according to the embodiment has the bipolar plate 31 described above, the flowability of the electrolytic solution can be improved and the pressure loss can be reduced, and at the same time, the electrolytic solution can be diffused over a wide area of the electrode to cause the battery reaction to occur over the entire area of the electrode. Can be uniformly generated. Therefore, the cell frame 3 can improve the battery reaction efficiency of the RF battery 1.

Since the cell stack 2 according to the embodiment includes the cell frame 3 described above, the battery reaction efficiency of the RF battery 1 can be improved.

Since the RF battery 1 according to the embodiment includes the cell stack 2 described above, the battery reaction efficiency is high.

Hereinafter, modified examples of the bipolar plate 31 according to the above-described embodiment will be described with reference to FIGS. 9 to 13. In the description of the modified example, differences from the above-described embodiment will be mainly described, and description of similar matters will be omitted.

[Modification 1]
Modification 1 of the bipolar plate 31 will be described with reference to FIGS. 9 and 10. In the above-described embodiment, as shown in FIG. 5, in the first tunnel 51 and the second tunnel 52, one first opening 61 and one second opening 62 are formed. explained. Modification 1 describes a configuration in which a plurality of first openings 61 and a plurality of second openings 62 are formed in each of the first tunnel 51 and the second tunnel 52.

FIG. 9 shows a bipolar plate 31 according to Modification 1A. In Modification 1A shown in FIG. 9, a plurality of first openings 61 are provided in the first tunnel 51 at intervals in the longitudinal direction of the first tunnel 51. Further, a plurality of second openings 62 are provided in the second tunnel 52 at intervals in the longitudinal direction of the second tunnel 52. In this example, the first opening 51 and the second opening 62 are provided at equal intervals along the longitudinal direction with respect to the first tunnel 51 and the second tunnel 52.

The planar shapes of the first opening 61 and the second opening 62 shown in the modification 1A are circular. In this example, the individual opening areas of the first opening 61 and the second opening 62 are equal. The first opening 61 and the second opening 62 are formed at positions aligned with each other in the width direction.

In Modification 1A, the distance between the center line of the first opening 61 and the center line of the second opening 62 (the dimension indicated by C ₆ in FIG. 9) is substantially the same in the longitudinal direction. .. When there are a plurality of first openings 61 as in Modification 1A, the center line of the first openings 61 is an approximate straight line passing through the center of the width (diameter) of each first opening 61. You should ask. When there are a plurality of second openings 62, the center line of the second openings 62 may be obtained as an approximate straight line passing through the center of the width (diameter) of each second opening 62.

In Modification 1A, the opening area of the first opening 61 and the opening area of the second opening 62 are substantially the same. When there are a plurality of first openings 61, the opening area of the first openings 61 is the total opening area of the first openings 61. When there are a plurality of second openings 62, the opening area of the second openings 62 is the total opening area of each second opening 62.

In Modification 1A, the case where the planar shapes of the first opening 61 and the second opening 62 are circular is illustrated, but the present invention is not limited to this. For example, as in Modification 1B shown in FIG. 10, the planar shapes of the first opening 61 and the second opening 62 may be rectangular. The planar shapes of the first opening 61 and the second opening 62 may be other shapes such as an oval shape and a polygonal shape. Examples of the polygonal shape include a triangular shape, a trapezoidal shape, a rhombic shape, and a hexagonal shape.

The numbers of the first openings 61 and the second openings 62 may be the same or different. Moreover, the planar shape and the opening area of each first opening 61 may be the same, or at least one of the planar shape and the opening area may be different. Furthermore, the first opening 61 and the second opening 62 may differ in at least one of the planar shape and the opening area.

[Modification 2]
A modified example 2 of the bipolar plate 31 will be described with reference to FIG. 11. In Modification 1A described above, as shown in FIG. 9, a configuration in which a plurality of first openings 61 and second openings 62 are formed has been described. When there are a plurality of first openings 61 and second openings 62, the first openings 61 and the second openings 62 are the first groove portions, respectively, as in Modification 2 shown in FIG. 11. 71 and the second groove 72 may be connected.

The first groove portion 71 shown in FIG. 11 is formed on the surface of one side of the bipolar plate 31 so as to connect the first opening portions 61 adjacent to each other in the longitudinal direction of the first tunnel 51. The first groove portion 71 does not extend to the first tunnel 51 and does not communicate with the first tunnel 51. Further, the second groove portion 72 is formed on the surface of the bipolar plate 31 on the one surface side so as to connect the second opening portions 62 adjacent to each other in the longitudinal direction of the second tunnel 52. The second groove 72 does not extend to the second tunnel 52 and does not communicate with the second tunnel 52.

[Modification 3]
Modification 3 of the bipolar plate 31 will be described with reference to FIG. In the above-described embodiment, as shown in FIG. 5, the configuration in which the opening area of the first opening 61 and the opening area of the second opening 62 are substantially the same has been described. As in Modification 3 shown in FIG. 12, the opening area of the first opening 61 and the opening area of the second opening 62 may be different.

In the third modification, as shown in FIG. 12, the case where the opening area of the second opening portion 62 is larger than the opening area of the first opening portion 61 is illustrated, but the present invention is not limited to this, and the first opening portion is not limited thereto. The opening area of the opening 61 may be larger than the opening area of the second opening 62.

The pressure of the electrolytic solution that has flowed to the electrodes is reduced by flowing through the electrodes. As shown in FIG. 12, when the opening area of the second opening 62 is larger than the opening area of the first opening 61, the effect of compensating for the pressure drop of the electrolytic solution in the electrode can be expected.

[Modification 4]
A modified example 4 of the bipolar plate 31 will be described with reference to FIG. In the above-described embodiment, as shown in FIG. 5, the configuration in which the cross-sectional areas of the first tunnel 51 and the second tunnel 52 are constant along the longitudinal direction has been described. As in Modification 4 shown in FIG. 13, the cross-sectional areas of the first tunnel 51 and the second tunnel 52 may change in the longitudinal direction.

The first tunnel 51 shown in FIG. 13 has a smaller cross-sectional area on the discharge side than on the supply side. "The cross-sectional area on the discharge side is smaller than that on the supply side" means that when the first tunnel 51 is divided into two sections in the longitudinal direction into two sections, the supply side and the discharge side, the average cross-sectional area of the section on the supply side. It means that the average value of the cross-sectional area of the discharge side section is smaller than the value. The second tunnel 52 has a larger cross-sectional area on the discharge side than on the supply side. “The cross-sectional area on the discharge side is larger than that on the supply side” means that when the second tunnel 52 is divided into two sections in the longitudinal direction into two sections on the supply side and the discharge side, the average cross-sectional area of the section on the supply side. It means that the average value of the cross-sectional area of the discharge side section is larger than the value. Regarding the average value of the cross-sectional area of each section on the supply side and the discharge side, a plurality of arbitrary points (for example, 10 points or more) are selected in the longitudinal direction, and the average value is obtained from the cross-sectional area at each point. Arbitrary points may be set at equal intervals along the longitudinal direction.

In Modified Example 4, as shown in FIG. 13, the cross-sectional area (specifically, the width) of the first tunnel 51 gradually decreases from the supply side toward the discharge side. On the other hand, the cross-sectional area (specifically, the width) of the second tunnel 52 gradually increases from the supply side to the discharge side.

In the bipolar plate 31 according to the modified example 4, the cross-sectional area of the first tunnel 51 is smaller on the discharge side than on the supply side, so that the cross-sectional area of the first tunnel 51 is constant in the longitudinal direction. Therefore, the pressure loss of the electrolytic solution along the longitudinal direction in the first tunnel 51 can be further reduced. In addition, since the cross-sectional area of the second tunnel 52 is larger on the discharge side than on the supply side, the cross-sectional area of the second tunnel 52 in the second tunnel 52 is larger than that in the case of being constant in the longitudinal direction. The pressure loss of the electrolytic solution along the longitudinal direction can be further reduced. Therefore, the bipolar plate 31 of Modification 4 can further reduce the pressure loss of the electrolytic solution flowing from the supply side to the discharge side.

In particular, when the cross-sectional area of the discharge side of the first tunnel 51 is made smaller than that of the supply side, the cross-sectional area of the first tunnel 51 is changed from the supply side to the discharge side at least in the portion where the first opening 61 is formed. It is preferable to decrease gradually. On the other hand, when increasing the cross-sectional area of the second tunnel 52 from the supply side to the discharge side, the cross-sectional area of the second tunnel 52 is changed from the supply side to the discharge side at least in the portion where the second opening 62 is formed. It is preferable to increase gradually.

[Modification 5]
Modification 5 of the bipolar plate 31 will be described with reference to FIGS. 14A and 14B. In the above-described embodiment, as shown in FIG. 5, each of the first tunnel 51 and the second tunnel 52 has a structure configured by one segment. At least one of the first tunnel 51 and the second tunnel 52 may have a structure including a plurality of segments 81, as in Modification 5 shown in FIGS. 14A and 14B.

Modified Example 5 exemplifies a case where each of the first tunnel 51 and the second tunnel 52 is composed of two segments 81 as shown in FIGS. 14A and 14B. The first tunnel 51 (second tunnel 52) is divided into two segments 81 in the width direction. One first opening 61 (second opening 62) is formed for each of the two segments 81. A wall portion 82 is provided between the adjacent segments 81 so as to divide the first tunnel 51 (second tunnel 52) in the width direction. As shown in FIG. 14B, in the wall portion 82, the bottom surface and the first opening portion 61 (second opening portion 62) are not opened inside the first tunnel 51 (second tunnel 52). Connect with the upper surface of the part. Therefore, in the first tunnel 51 (second tunnel 52), the upper surface of the portion where the first opening 61 (second opening 62) is not formed is supported by the wall 82. Therefore, when the first tunnel 51 (second tunnel 52) is composed of a single tunnel without the wall portion 82 by dividing the width direction into a plurality of segments 81 by the wall portion 82. Compared with, the structural strength can be improved. In addition, as shown in FIG. 14A, when the wall portion 82 is provided over the entire length in the longitudinal direction of the first tunnel 51 (second tunnel 52), further improvement in structural strength can be expected. This is because the wall portion 82 extending over the entire length of the first tunnel 51 (second tunnel 52) functions as a rib that reinforces the structural strength of the first tunnel 51 (second tunnel 52).

In particular, the larger the cross-sectional area of the first tunnel 51 (second tunnel 52), specifically, the wider the width, the lower the structural strength of the first tunnel 51 (second tunnel 52) is likely to be. When the cross-sectional area (width) of the first tunnel 51 (second tunnel 52) is large, the structural strength is reduced by dividing the first tunnel 51 (second tunnel 52) into a plurality of segments 81. Can be effectively suppressed.

Further, in this example, as shown in FIG. 14A, the wall portion 82 is provided over the entire longitudinal direction of the first tunnel 51 (second tunnel 52). The wall portion 82 may be provided only in a portion of the first tunnel 51 (second tunnel 52) where the first opening portion 61 (second opening portion 62) is not formed. Specifically, in the first tunnel 51, between the first edge portion 311 and the supply-side end portion 611 of the first opening 61, and the discharge-side end portion 512 of the first tunnel 51. The wall portion 82 may be provided only between the first opening portion 61 and the discharge-side end portion 612. In addition, in the second tunnel 52, between the second edge 312 and the discharge side end 622 of the second opening 62, and between the supply side end 521 and the second end of the second tunnel 52. The wall portion 82 may be provided only between the opening portion 62 and the end portion 621 on the supply side.

Further, as shown in FIG. 15, when the cross-sectional area (specifically, the width) of the first tunnel 51 (second tunnel 52) changes in the longitudinal direction, the wall portion 82 is formed only in a portion having a large cross-sectional area. May be provided. The first tunnel 51 shown in FIG. 15 has a smaller cross-sectional area on the discharge side than on the supply side, as in the modified example 4 shown in FIG. The second tunnel 52 has a larger cross-sectional area on the discharge side than on the supply side. In this case, in the first tunnel 51, the wall portion 82 may be provided only on the supply side having a large cross-sectional area. That is, the wall portion 82 is provided between the first edge portion 311 and the supply-side end portion 611 of the first opening portion 61. Moreover, in the second tunnel 52, the wall portion 82 may be provided only on the discharge side having a large cross-sectional area. That is, the wall portion 82 is provided between the second edge portion 312 and the discharge-side end portion 622 of the second opening portion 62. By providing the wall portion 82 only in a portion where the cross-sectional area of the first tunnel 51 (second tunnel 52) is large, it is possible to effectively suppress a decrease in the structural strength of the first tunnel 51 (second tunnel 52). it can.

1 Redox flow battery (RF battery)
2 cell stack 10 battery cell 11 membrane 12 positive electrode cell 13 negative electrode cell 14 positive electrode 15 negative electrode 3 cell frame 31 bipolar plate 311 first edge 312 second edge 32 frame 32o recess 33, 34 liquid supply manifold 35 , 36 Drainage manifold 33s, 34s Liquid feed slit 35s, 36s Drainage slit 37 Seal member 38 Seal groove 330 Supply side rectification section 350 Discharge side rectification section 51 First tunnel 512 Discharge side end 512a First flow obstruction Structure 52 Second tunnel 521 Supply side end 521a Second flow obstruction structure 61 First opening 62 Second opening 611, 621 Supply side end 612, 622 Discharge side end 71 First Groove portion 72 Second groove portion 81 Segment 82 Wall portion 100P Positive electrode circulation flow passage 100N Negative electrode circulation flow passage 106 Positive electrode electrolyte tank 107 Negative electrode electrolyte tank 108, 109 Forward pipe 110, 111 Return pipe 112, 113 Pump 200 Sub-stack 210 Supply/discharge plate 220 End plate 230 Tightening mechanism 80 AC/DC converter 90 Electric power system

Claims (12)

A bipolar plate arranged facing the electrode, having a supply-side first edge to which an electrolytic solution is supplied and a discharge-side second edge to which the electrolytic solution is discharged,
A first tunnel and a second tunnel that are adjacent to each other are provided,
The first tunnel is formed inside the bipolar plate, has an opening at the first edge, and has an end on the discharge side,
The first tunnel has a first opening opening on the surface of the electrode side,
The discharge side end of the first tunnel has a first flow inhibition structure that inhibits the flow of the electrolytic solution from the first tunnel to the second edge,
The second tunnel is formed inside the bipolar plate, has an opening at the second edge, and has an end on the supply side,
The second tunnel has a second opening opening on the surface of the electrode side,
The end on the supply side in the second tunnel has a second flow obstruction structure that obstructs the flow of the electrolytic solution from the first edge to the second tunnel,
Bipolar plate. The bipolar plate according to claim 1, wherein the supply-side and discharge-side ends of the first opening and the supply-side and discharge-side ends of the second opening are closed. The opening area of the first opening is smaller than the plane cross-sectional area of the first tunnel,
The bipolar plate according to claim 1 or 2, wherein an opening area of the second opening is smaller than a plane sectional area of the second tunnel. A cross ratio in which the ratio of the width of the first opening to the circumference of the first tunnel and the ratio of the width of the second opening to the circumference of the second tunnel is less than 50%. The bipolar plate according to any one of claims 1 to 3, which has a surface. The distance between the supply-side end of the first opening and the first edge, and the distance between the supply-side end of the second opening and the first edge are substantially Is identical to, and
The distance between the discharge-side end of the first opening and the second edge and the distance between the discharge-side end of the second opening and the second edge are substantially. 5. The bipolar plate according to claim 1, wherein at least one of the above is satisfied. The first tunnel has a smaller cross-sectional area on the discharge side than on the supply side; and
The bipolar plate according to any one of claims 1 to 5, wherein the second tunnel has at least one of a larger cross-sectional area on the discharge side than on the supply side. The bipolar plate according to any one of claims 1 to 6, wherein the distance between the center line of the first opening and the center line of the second opening is substantially the same in the longitudinal direction. .. The bipolar plate according to any one of claims 1 to 7, wherein an opening area of the first opening and an opening area of the second opening are substantially the same. The bipolar plate according to any one of claims 1 to 8, wherein the opening areas per unit length of the first opening and the second opening are substantially the same in the longitudinal direction. A bipolar plate according to any one of claims 1 to 9;
A frame provided on the outer periphery of the bipolar plate,
Cell frame. The cell frame according to claim 10,
Cell stack. Comprising the cell stack of claim 11.
Redox flow battery.

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