WO2019030903A1 - Cell stack and redox flow battery - Google Patents

Abstract

This cell stack is provided with: a stacked body in which a plurality of redox flow battery cells are stacked; a pair of end plates sandwiching the stacked body; and a plurality of binding members which are arranged in outer edge regions of both end plates, and which bind the end plates together. The end plates have a rectangular planar shape. The length x of one side of the rectangle is not less than 100 mm and not more than 2000 mm. The number y of the binding members arranged on one side of the rectangle is a natural number such that 0.0025x ≤ y ≤ 0.014x + 5 is satisfied.

Description

Cell stack and redox flow battery

The present invention relates to a cell stack and a redox flow battery.

One of the storage batteries is a redox flow battery (hereinafter sometimes referred to as an RF battery) in which a battery reaction is performed by supplying an electrolytic solution to an electrode. As described in Patent Document 1, an RF battery includes a positive electrode supplied with a positive electrode electrolyte, a negative electrode supplied with a negative electrode electrolyte, and a diaphragm (ion exchange membrane) interposed between both electrodes. A battery cell comprising the A battery cell is constructed using a cell frame typically provided with a bipolar plate and a frame provided on the periphery of the bipolar plate (FIG. 7 of Patent Document 1). An RF battery is typically used in a form called a cell stack in which a plurality of battery cells are stacked (FIG. 1, FIG. 7, etc. in Patent Document 1). The cell stack is formed by sandwiching the stack of battery cells with a pair of end plates from both sides, and stacking in the stacking direction of the stack by a tightening shaft passing through both end plates and a nut provided at an end of the tightening shaft The body is tightened (Patent Document 1 [0004]).

JP, 2012-099368, A

The cell stack of the present disclosure is
A laminate in which a plurality of redox flow battery cells are laminated;
A pair of end plates sandwiching the laminate;
And a plurality of clamping members disposed in outer edge regions of both end plates and clamping between the two end plates,
The end plate has a rectangular planar shape,
The length x of one side of the rectangle is 100 mm or more and 2000 mm or less,
The number y of the clamping members arranged on one side of the rectangle is
It is a natural number that satisfies 0.0025x ≦ y ≦ 0.014x + 5.

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

The redox flow battery of embodiment WHEREIN: It is a graph which shows the range of the length of the one side of the end plate with which a cell stack is equipped, and the number of clamping members. In Experiment 1, it is a graph which shows the relationship between the length of one side (long side) of an end plate, and the number of clamping members. In Experiment 1, it is a graph which shows the relationship between the length of one side (short side) of an end plate, and the number of clamping members. In Experiment 2, it is a graph which shows the relationship between the length of the one side of an end plate, and the number of clamping members. The redox flow battery of embodiment WHEREIN: It is explanatory drawing explaining the state which arrange | positioned the clamping member to the end plate with which a cell stack is equipped. It is a schematic block diagram which shows the cell stack of embodiment, and a disassembled perspective view which shows the redox flow battery cell with which a cell stack is equipped. It is a schematic block diagram which shows the redox flow battery of embodiment.

[Problems to be solved by the invention]
With respect to a redox flow battery (RF battery) including the above-described battery cell stack, it is desirable to be able to reduce an increase in internal pressure of the battery cell while preventing excessive deformation of the end plate. This is because, in the worst case, the components of the battery cell may be damaged by the increase of the internal pressure.

The rise in internal pressure is caused, for example, by changing the temperature when the operation of the RF battery is stopped in a state in which the battery cell is filled with the electrolytic solution, and the electrolysis is stored in the battery cell, typically in the cell frame. What arises due to thermal expansion of the liquid is mentioned. When the electrolyte is thermally expanded, a force is applied to each cell frame from the opening (window) side of the frame to the outer edge side. When each cell frame is in a state of being firmly restrained by the end plate and hard to be elastically deformed, the stress applied to the cell frame is increased by the above-described pressing force, and the internal pressure of the battery cell is increased. If the increase in internal pressure is too large, the stress may be too large, which may lead to breakage of battery cell components such as cracking or cracking of the cell frame, particularly the frame. On the other hand, when the restraint by the end plate is weak, each cell frame is easily elastically deformed when receiving the above-mentioned pressing force, but there is a possibility that the end plate may be deformed excessively and the electrolyte may leak from adjacent battery cells. .

An object of the present disclosure is to provide a cell stack that can suppress excessive deformation of the end plate and that the internal pressure of the battery cell is less likely to rise. In addition, another object of the present disclosure is to provide a redox flow battery which can suppress excessive deformation of the end plate and which is difficult to increase the internal pressure of the battery cell.

[Effect of the present disclosure]
The cell stack of the present disclosure and the redox flow battery of the present disclosure can suppress excessive deformation of the end plate, and the internal pressure of the battery cell does not easily rise.

Description of an embodiment of the present invention
First, embodiments of the present invention will be listed and described.
(1) A cell stack according to an aspect of the present invention is
A laminate in which a plurality of redox flow battery cells are laminated;
A pair of end plates sandwiching the laminate;
And a plurality of clamping members disposed in outer edge regions of both end plates and clamping between the two end plates,
The end plate has a rectangular planar shape,
The length x of one side of the rectangle is 100 mm or more and 2000 mm or less,
The number y of the clamping members arranged on one side of the rectangle is
It is a natural number that satisfies 0.0025x ≦ y ≦ 0.014x + 5.
The clamping members arranged on one side of the rectangle are typically arranged uniformly (details will be described later).

In the cell stack described above, it can be said that the clamping member disposed in the outer edge region of the end plate and clamping the laminate satisfies the above-mentioned specific range, and is appropriately provided with a restraint point by the clamping member. In detail, it can be said that the laminate is not excessively restrained by the end plate by not having too many tightening members, and the cell frame constituting the laminate, in particular, the frame can be elastically deformed to some extent. In a redox flow battery (RF battery) provided with such a cell stack as described above, the temperature changes when the operation is stopped in a state in which the electrolytic solution is filled in the battery cell, and the electrolysis is stored in the battery cell Even when a force is generated to press each cell frame due to the thermal expansion of the liquid, the stress applied to the cell frame can be relaxed by elastically deforming each cell frame. Therefore, according to the above-described cell stack, it is possible to construct an RF battery in which the internal pressure of the battery cell is difficult to increase due to thermal expansion of the electrolyte, and the components of the battery cell are not easily damaged due to the increase of the internal pressure. . And, by not having too few clamping members, the laminate is properly restrained by the end plate. Therefore, in the RF battery provided with the above-described cell stack, excessive deformation of the end plate can be suppressed even if hydraulic pressure accompanying the flow of the electrolyte acts on the end plate during operation. Therefore, the above cell stack can hold the laminate of the RF battery cells in a liquid-tight manner, and can construct an RF battery in which the electrolytic solution is unlikely to leak from between adjacent RF battery cells.

(2) As an example of the above cell stack,
The number of the clamping members disposed on the long side of the rectangle may be equal to or greater than the number of the clamping members disposed on the short side of the rectangle.

The above-mentioned form tends to increase the number of tightening members disposed on the long side which is relatively less rigid among the long side and the short side of the end plate while reducing the rise of the internal pressure of the battery cell as described above In the above, it is easy to suppress excessive deformation of the end plate and the electrolyte is less likely to leak.

(3) As an example of the above cell stack,
The number y of the fastening members may be in a form satisfying 0.00333x ≦ y.

Since the said form reduces the raise of the internal pressure of a battery cell as mentioned above, since there are more numbers of clamping members, it is easy to suppress an excessive deformation | transformation of an end plate more, and electrolyte solution leaks less.

(4) As an example of the above cell stack,
The number y of the fastening members may be such that y ≦ 0.012x + 4.

In the above-described embodiment, the electrolytic solution is less likely to leak as described above, and the number of tightening members is smaller. Therefore, the above-described stress can be easily relieved, and the internal pressure of the battery cell is more difficult to increase.

(5) The redox flow battery (RF battery) according to one aspect of the present invention is
The cell stack according to any one of the above (1) to (4) is provided.

Since the above-described RF battery includes the above-described cell stack in which the restraint by the fastening member is appropriate, the internal pressure of the battery cell is unlikely to increase due to the thermal expansion of the electrolyte as described above. In addition to preventing damage to the components of the battery cell, it is easy to suppress excessive deformation of the end plate to prevent leakage of the electrolytic solution from between adjacent battery cells.

[Details of the Embodiment of the Present Invention]
Embodiments of the present invention will be specifically described below with reference to the drawings. In the figures, the same reference numerals indicate the same names.

[Embodiment]
First, an outline of the redox flow battery (RF battery) 10 according to the embodiment will be described mainly with reference to FIGS. 6 and 7. Next, the details of the end plate 32 and the fastening member 33 will be described mainly with reference to FIG.
The ions shown in the positive electrode tank 16 and the negative electrode tank 17 of FIG. 7 show examples of ion species contained in the electrolyte solution of each electrode.

(Overview of RF battery)
As shown in FIG. 7, the RF battery 10 according to the embodiment includes at least one battery cell (RF battery cell) 10C and a circulation mechanism for circulating and supplying the electrolytic solution to the battery cell 10C. In particular, the RF battery 10 of the embodiment is a multi-cell battery including the cell stack 30 of the embodiment that mainly includes the laminate 100 in which the plurality of battery cells 10C are stacked.

The RF battery 10 is typically connected to the power generation unit 420 and a load 440 such as a power system or a customer via the AC / DC converter 400 or the transformation equipment 410, and the power generation unit 420 is supplied with power. It charges as a source and discharges the load 440 as a power supply target. Examples of the power generation unit 420 include a solar power generator, a wind power generator, and other general power plants.

<Battery cell>
The battery cell 10C includes a positive electrode 14 to which a positive electrode electrolyte is supplied, a negative electrode 15 to which a negative electrode electrolyte is supplied, and a diaphragm 11 interposed between the positive electrode 14 and the negative electrode 15.
The positive electrode 14 and the negative electrode 15 are reaction sites to which an electrolytic solution containing an active material is supplied to cause a battery reaction of the active material (ion), and a porous material such as a fiber aggregate of a carbon material is used.
The diaphragm 11 is a member that separates the positive electrode 14 and the negative electrode 15 from each other and transmits a predetermined ion, and an ion exchange membrane or the like is used.

<Cell frame>
Battery cell 10C is typically constructed using cell frame 20 illustrated in FIG. The cell frame 20 includes a bipolar plate 21 and a frame 22 provided on the periphery of the bipolar plate 21.

Typically, the bipolar plate 21 is a conductive member in which the positive electrode 14 is disposed on one side, the negative electrode 15 is disposed on the other side, and a current flows but an electrolyte does not pass. The bipolar plate 21 is, for example, a conductive plastic plate containing graphite and the like and an organic material.

The frame 22 includes a window 22 w in which the positive electrode 14 and the negative electrode 15 and the bipolar plate 21 are disposed, a supply path for supplying an electrolytic solution to the positive electrode 14 and the negative electrode 15, and the positive electrode 14 and the negative electrode 15. And a discharge path for discharging the electrolyte solution from the In FIG. 6, the case where the positive electrode supply passage and the positive electrode discharge passage are provided on one surface side of the frame 22 and the negative electrode supply passage and the negative electrode discharge passage are provided on the other surface side of the frame 22 is illustrated. The positive electrode supply passage and the negative electrode supply passage have liquid supply holes 24i and 25i, and slits 26i and 27i extending from the liquid supply holes 24i and 25i to the window 22w. The positive electrode discharge path and the negative electrode discharge path include drain holes 24o and 25o, and slits 26o and 27o extending from the window 22w to the drain holes 24o and 25o. Each of the holes 24 i, 24 o, 25 i, 25 o is a through hole penetrating the front and back of the frame 22. The slits 26 i and 26 o on the positive electrode side are provided on one surface of the frame 22. The slits 27 i and 27 o on the negative electrode side are provided on the other surface of the frame 22. In the cell stack 30, the plurality of cell frames 20 are stacked, whereby the liquid supply holes 24i and 25i and the drain holes 24o and 25o respectively form a flow channel of the electrolytic solution.

The frame 22 of this example surrounds the window 22w, and the seal material 18 is disposed on the outer edge side of the liquid supply holes 24i, 25i and the drain holes 24o, 25o. In the cell stack 30, the sealing material 18 is interposed between the frames 22 and 22 (see also FIG. 7). The seal member 18 is made of an elastic material or the like, and the laminates 100 are clamped by the end plates 32 and 32 and the fastening members 33 as described later, thereby maintaining the frames 22 and 22 in a liquid tight manner.

The constituent material of the frame 22 is excellent in insulation, and does not react with the electrolytic solution, and a resin having resistance (chemical resistance, acid resistance, etc.) to the electrolytic solution, for example, vinyl chloride, polyethylene, polypropylene, etc. is used. .

The planar shape of the bipolar plate 21 (the window 22w), the frame 22, the positive electrode 14 and the negative electrode 15 described above is typically a rectangle shown in FIG. In addition, the above-mentioned planar shape includes a curved shape such as a circle and an ellipse, and a polygonal shape such as a hexagon. If the planar shape is rectangular as in this example, the laminated body 100 has a rectangular shape and is easy to handle. The end plates 32 sandwiching the rectangular parallelepiped laminate 100 are rectangular as will be described later, and the fastening members 33 are equally arranged in the rectangular frame-like outer edge side area 35. Therefore, in the laminated body 100, the tightening member 33 is uniformly disposed in the circumferential direction, and the tightening force by the end plate 32 and the tightening member 33 tends to be uniformly applied.

<Cell stack>
The cell stack 30 includes a stacked body 100 in which a plurality of cell frames 20 (bipolar plates 21), a positive electrode 14, a diaphragm 11, and a negative electrode 15 are stacked in this order, a pair of end plates 32 and 32 sandwiching the stacked body 100, and both A plurality of clamping members 33 disposed in the outer peripheral area 35 of the end plates 32, 32 and clamping between the end plates 32, 32 are provided. When the end plates 32, 32 are tightened by the tightening member 33, the stacked body 100 is held in the stacked state by the tightening force in the stacking direction. Further, the laminated body 100 is held in a liquid-tight manner by crushing the sealing material 18 by the tightening force. The number of battery cells 10C in the laminate 100 can be appropriately selected.

The end plate 32 is a member that sandwiches the stacked body 100, directly receives a tightening force by the tightening member 33, and causes the received force to act on the stacked body 100. The end plate 32 has an annular outer edge region 35 extending from the outer edge of the laminate 100 to the outer edge 32 o of the end plate 32 when viewed through in the stacking direction of the laminate 100 with the laminate 100 interposed therebetween. And is larger than the outer edge of the laminate 100 (see also FIG. 5). The outer edge area 35 is an arrangement area of the tightening member 33. The size of the outer edge side region 35 (protruding length from the laminate 100) may be adjusted according to the size of the laminate 100, the tightening member 33, and the like.

In addition, the cell stack 30 can include a stack 100 in which a predetermined number of battery cells 10C are used as a sub-cell stack and a plurality of sub-cell stacks are stacked. The subcell stack can include an electrolyte supply / discharge plate portion. FIG. 6 exemplifies a case where a plurality of subcell stacks including a supply and discharge plate portion are provided. In the cell frames positioned at both ends in the stacking direction of the battery cells 10C in the sub-cell stack or the laminate 100, a bipolar plate 21 may be used or a current collector plate made of metal or the like may be arranged together with the bipolar plate 21. .

<Circulation mechanism>
As shown in FIG. 7, the circulation mechanism includes a positive electrode tank 16 storing positive electrode electrolyte to be supplied to the positive electrode 14, a negative electrode tank 17 storing the negative electrode electrolyte to be supplied to the negative electrode 15, and a positive electrode tank 16. Piping 162, 164 which connects between the cell stacks 30, piping 172, 174 which connects between the negative electrode tank 17 and the cell stack 30, and pumps 160, 170 provided in the piping 162, 172 on the supply side are provided. The pipes 162, 164, 172, and 174 are connected to flow channels by the liquid supply holes 24i and 25i and the drain holes 24o and 25o, respectively, to construct a circulation path of the electrolyte of each electrode.

For the basic configuration, materials, electrolyte solution and the like of the RF battery 10, known configurations, materials, electrolyte solution and the like can be appropriately used. For example, electrolytes other than the vanadium-based electrolyte illustrated in FIG. 7 can be used.

(Details of end plate and tightening member)
The end plate 32 provided in the RF battery 10 of the embodiment and the cell stack 30 of the embodiment has a rectangular planar shape as illustrated in FIG. 5. In the end plate 32, the number of the fastening members 33 disposed in the rectangular frame-like outer edge side area 35 along the outer edge 32o satisfies the specific range described later. In FIG. 5, the outer edge side area 35 is hatched with a two-dot chain line for easy understanding. Further, in FIG. 5, the tightening members 33 (a to e, A to D) are indicated by white circles. The rectangle here also includes a square (as well as the components of the above-described laminate 100).

<Length x of one side>
The length x of one side of the rectangle drawn by the outer edge 32 o of the end plate 32, that is, the length L of the long side and the length H of the short side can be appropriately selected according to the size of the laminate 100. For example, the length x of at least one of the long side length L and the short side length H may be 100 mm or more and 2000 mm or less (however, the short side length H ≦ long side length L) . The RF battery 10 may be provided with an end plate 32 having a length x of less than 100 mm or more than 2000 mm.

If the above-mentioned length x is 100 mm or more, in particular if the short side length H is 100 mm or more, the practical RF battery 10 can be obtained. As the length x is larger, the laminate 100 is also larger, and the RF battery 10 with high output can be obtained. If the length x is 2000 mm or less, particularly if the length L of the long side is 2000 mm or less, the components of the laminate 100 and the cell stack 30 are not too large, and it is easy to construct them. If both the long side length L and the short side length H are 100 mm or more and 2000 mm or less, it is easy to construct, and it is easy to make the high-power RF battery 10.

From the viewpoint of increasing the output and the like, the above-mentioned length x may be 200 mm or more, 300 mm or more, and particularly, the long side length L may be 400 mm or more, 500 mm or more. From the viewpoint of ease of handling and reduction of manufacturing errors, the length x may be, for example, 1900 mm or less, or 1800 mm or less.

<Number of tightening members y>
When the length x is in the range of 100 mm to 2000 mm, the number y of the fastening members 33 disposed on one side of the rectangle drawn by the outer edge 32 o of the end plate 32, ie, at least one of the long side and the short side, is 0. It is satisfied that ≦ x ≦ y ≦ 0.014x + 5. The number y is a natural number. FIG. 1 is a graph showing the relationship between the length x (mm) of one side and the number y of the fastening members 33 on one side, in which a region satisfying 0.0025x ≦ y ≦ 0.014x + 5 is hatched. . In the graph of FIG. 1, the horizontal axis indicates the length x (mm) of one side of the rectangle, and the vertical axis indicates the number y of clamping members disposed on one side of the rectangle.

When the number y of the fastening members 33 arranged on the long side and the short side satisfies 0.0025x ≦ y, the length x of one side is long and the fastening member is long even if the large end plate 32 is provided. The number y of 33 is not too small, and the stack member 100 can be appropriately restrained by the fastening member 33. For example, during operation of the RF battery 10, excessive deformation of the end plate 32 can be suppressed even if hydraulic pressure or the like accompanying the flow of the electrolyte acts on the cell stack 30. When the number y of the fastening members satisfies 0.00333x ≦ y, it is possible to further suppress excessive deformation of the end plate 32. When the length x is less than 400 mm, the value of 0.0025 x is less than 1, but it is practical to set the number y to 2 or more.

When the number y of the fastening members 33 arranged on the long side and the short side satisfies y ≦ 0.014x + 5, the fastening members are long even if the length x of one side is long and the large end plate 32 is provided. The number y of 33 is not too large, and the clamping member 33 can exert an appropriate restraining force on the end plate 32. Therefore, when the operation of the RF battery 10 is stopped in a state where the battery cell 10C is filled with the electrolytic solution, the electrolytic solution in the battery cell 10C thermally expands due to a temperature change, and the frame 22 is viewed from the window 22w side Even when pressed to the outer edge side, the frame 22 can be elastically deformed. The elastic deformation can relieve the stress applied to the cell frame 20. This stress relaxation can make it difficult to increase the internal pressure of the battery cell 10C. Therefore, damage to the components of the battery cell 10C, such as cracks or cracks in the frame 22, due to the increase in the internal pressure can be prevented. When the number y of the fastening members satisfies y ≦ 0.012x + 4, the internal pressure of the above-described battery cell 10C is more difficult to increase.

The number y1 of the fastening members 33 arranged on the long side of the rectangle can be equal to or more than the number ys of the fastening members 33 arranged on the short side of the rectangle Number of sides y). The long side is considered to be more easily deformed because the length is longer than the short side (H ≦ L). If ys ≦ yl is satisfied, it is easy to increase the number y of the fastening members 33 disposed on the long side. Therefore, it is easier to suppress the above-mentioned excessive deformation of the end plate 32 and the like, and it is easier to prevent the leakage of the electrolytic solution from between the adjacent battery cells 10C and 10C.

When the number y1 of the fastening members 33 on the long side at least satisfies 0.0025x ≦ y1 ≦ 0.014x + 5, the above-mentioned effect of reducing the increase in internal pressure and the effect of suppressing excessive deformation can be obtained. When both the number y1 of the fastening members 33 on the long side and the number ys of the fastening members 33 on the short side satisfy 0.0025x ≦ y1, ys ≦ 0.014x + 5 It is easier to obtain the reduction effect and the excessive deformation suppression effect. In this case, the difference between the number y1 on the long side and the number ys on the short side changes in a range satisfying 0.0025x ≦ y1 and ys ≦ 0.014x + 5.

The number yl of the fastening members 33 on the long side can also be smaller than the number ys of the fastening members 33 on the short side (however, 0.0025x ≦ yl ≦ 0.014x + 5 is satisfied). In this case, in the frame 22 of the cell frame 20, a region constrained by the long side of the end plate 32 is easily elastically deformed, and it is expected that the above-described reduction effect of the rise in internal pressure is more easily obtained.

When the length x is in the range of 100 mm to 2000 mm, depending on the length x, the number y1 of the fastening members 33 on the long side is, for example, 2 to 25 or less, the fastening on the short side The number ys of the members 33 is, for example, about 2 or more and 20 or less.

<Arrangement condition of tightening member>
In the rectangular end plate 32, the clamping members 33 of the number y arranged on one side of the length x are typically arranged evenly. The uniform arrangement means that the distance between the adjacent tightening members 33, 33 is equal to one side of the length x so that the geometrically uniform length can be obtained by the length x / (number y-1). It means that the fastening member 33 of y is arrange | positioned. In addition, in one side of the length x, a portion may be included in which the distance between the adjacent tightening members 33, 33 is 70% or more and 130% or less of the equal length. This will be specifically described with reference to FIG. For example, when the clamping members a to e of several yl = 5 are arranged on the long side of the length L, the adjacent clamping members (a, b), (b, c), (c, d), (d) The intervals La, Lb, Lc, and Ld of and e) are each equal to L / 4 if they have an equal length. When including a portion having a substantially uniform length, for example, when the spacing between the fastening members (b, c) has a substantially uniform length, this spacing is 70% of the uniform length Lb (= Lb × 70). % = _{L S)} or more, 130% of the equivalent length Lb (= La × 130% = is _{L L)} or less.

Alternatively, for example, in the case of arranging clamping members A to D with several ys = 4 on the short side of the length H, adjacent clamping members (A, B), (B, C), (C, D) The intervals H _A , H _B and H _c are respectively H / 3 if they have an equal length. The short side can also include a portion having a substantially uniform length, as in the case of the long side described above.

<Others>
If the end plate 32 is provided with a flat plate body and ribs projecting from the plate body as shown in FIG. 6, the strength can be enhanced and the weight can be reduced even if the thickness of the plate body is reduced to some extent. be able to. Although the grid-like rib is illustrated in FIG. 6, the shape of the rib can be changed as appropriate. If the ribs are omitted and only the plate body is used, a thick plate can increase the strength.

The fastening member 33 includes, for example, a bolt 330 screwed at both ends and provided with a bolt 330 disposed between the end plates 32, 32 and a nut 332 attached to the end of the bolt 330. . As the bolt 330 and the nut 332, those having sizes standardized by JIS or ISO can be appropriately used. The thicker the bolt 330 is, the larger the clamping force can be obtained, so the bolt 330 can be made thicker according to the length x. However, in this case, the outer edge area 35 of the end plate 32 becomes large, and the weight of the end plate 32 tends to increase. On the other hand, when the number y of the fastening members 33 satisfies 0.0025x ≦ y ≦ 0.014x + 5 in the range where the above-mentioned length x is 100 mm or more and 2000 mm or less, the size is typically a certain size. The bolt 330 and the nut 332 of (for example, M20) can be commonly used.

The constituent material of the end plate 32 and the fastening member 33 is excellent in strength if it is a metal, particularly an iron-based material such as steel.

(Use)
The RF battery 10 according to the embodiment is a storage battery for the purpose of stabilizing the fluctuation of the power generation output, storing power when surplus of generated power, load leveling, etc. for power generation of natural energy such as solar power generation and wind power generation. Available. In addition, the RF battery 10 of the embodiment is juxtaposed to a general power plant, and can be used as a storage battery for the purpose of the countermeasure against the instantaneous drop / blackout and the load leveling.

(effect)
In the RF battery 10 of the embodiment including the cell stack 30 of the embodiment, the number y of the fastening members 33 disposed in the outer edge area 35 of the end plate 32 corresponds to the length x of one side of the rectangular end plate 32. The above-described specific range is satisfied, and the restraint point by the fastening member 33 is appropriately provided. Therefore, the temperature of the RF battery 10 changes when the operation is stopped in a state where the battery cell 10C is filled with the electrolytic solution, and the electrolytic solution stored in the battery cell 10C is thermally expanded. It is difficult for the internal pressure of the battery cell 10C to rise due to the thermal expansion of the electrolytic solution. In addition, the RF battery 10 can suppress excessive deformation of the end plate 32 during operation. These effects are specifically described in the following test examples.

[Test Example 1]
With respect to the end plate provided in the above-described cell stack and RF battery, the deformation state of the end plate was investigated by variously changing the lengths of the long side and the short side and the number y of the fastening members.

In this test, using an bolt and a nut as a fastening member for an end plate having a length L (mm) of the long side and a length H (mm) of the short side shown in Table 1, the following conditions Find the amount of deformation when tightening with. Here, maximum deflection δmax (mm) on the long side and maximum deflection δmax (mm) on the short side are determined as follows, and are shown in Table 1.
For the long side of the end plate, the distance between adjacent bolts on the long side (long side length L / (number of bolts on the long side: yl-1)) is the beam length a, adjacent bolts on the short side Distance (short side length H / (short side side number of bolts ys-1)) width of the beam, thickness of the end plate height of the beam t, Young's modulus of the end plate Young's modulus of the beam E, the maximum deflection δmax of the free end static determination beam whose hydraulic load is the distributed load P of the beam is determined.
For the short side of the end plate, the distance between the adjacent bolts on the short side (short side length H / (number of bolts on the short side ys-1)) is the beam length a, and the adjacent bolts on the long side The maximum deflection δmax of the free end stationary beam is determined in the same manner as the long side, assuming that the interval of (long side length L / (long side side bolt number yl-1)) is the beam width b.
The maximum deflection δmax is expressed as follows using the second moment of area I (= (b × t ³ ) / 12) according to the equation of deflection of the beam.
δmax = 5 × P × b × (a ⁴ ) / (384 × E × I)

(conditions)
Young's modulus E = 206 GPa (in this case, the end plate is made of rolled steel for general structure, and Young's modulus of rolled steel for general structure is adopted)
Thickness t = 75 mm
Number of bolts y1 on the long side, number ys of bolts on the short side = value shown in Table 1, in this case the number ys on the short side ≦ the number y of long sides
Bolt placement condition Bolts are evenly placed on each of the long side and short side (see Fig. 5).
Fluid pressure P = 0.64MPa, evenly distributed load The size of bolt and nut is constant (eg, M20 equivalent bolt)

(Evaluation judgment)
It can be said that the smaller the maximum deflection δmax, the less the deflection of the end plate and the less the deformation thereof. Here, among the maximum deflection δmax on the long side and the maximum deflection δmax on the short side, a larger value is set as the maximum deflection δMAX, and the case where the maximum deflection δMAX exceeds 0.38 mm (0.38 <δMAX) is deformed. It is evaluated as B as easy. When the maximum deflection δMAX is more than 0.076 mm and 0.38 mm or less (0.076 <δMAX ≦ 0.38), it is evaluated as G as being difficult to deform. When the maximum deflection δMAX is less than or equal to 0.076 mm (δMAX ≦ 0.076), it is evaluated as VG that is very difficult to deform. The results are shown in Table 1. Here, the maximum deflection δmax on the long side is often equal to or greater than the maximum deflection δmax on the short side.

In addition, by tightening the end plate, as described above, the seal material provided in the laminated body is crushed and made liquid-tight. The crushing margin of the sealing material is preferably about 8% to 40% of the thickness of the sealing material, although it depends on the size of the cell stack and the sealing material. For example, in the case of an O-ring having a diameter of 変 化 2.4 mm, the change width of the desirable crushing margin range (0.2 mm to 0.96 mm) is 0.76 mm. Therefore, here, with respect to the range of the crushing margin of the sealing material, 0.38 mm, which is the maximum change width due to the deformation of the end plate being 1/2 at maximum, is taken as the allowable upper limit value of the maximum deflection δMAX. A case where the width is at most 1/2 or less, that is, 0.38 mm or less is evaluated as G. Assuming that the variation width is 0.076 mm, which is the maximum 1/10, as the preferable allowable upper limit value of the maximum deflection δMAX described above, and the variation is the maximum 1/10 or less, that is, the case where it is 0.076 mm or less. Evaluate.

As shown in Table 1, sample nos. 1 to No. In all cases 10, the maximum deflection δMAX is small (here, 0.38 mm or less), and the evaluation is G or VG. It can be seen that the end plate is unlikely to undergo excessive deformation even when receiving hydraulic pressure or the like. Sample No. 4 to No. 10 shows that the maximum deflection δMAX is smaller (here, less than 0.076 mm), and the end plate is more difficult to deform. On the other hand, for sample no. 101 to No. In all cases, the maximum deflection δmax is large (here, 0.47 mm or more, and the maximum deflection δMAX is 0.75 mm or more), and the evaluation is B. 1 to No. It turns out that it is easier to deform than 10.

Sample No. 1 to No. Sample No. 10 has a small maximum deflection. 101 to No. The reason why the maximum deflection of 104 is larger is considered as follows. FIG. 2 is a graph showing the relationship between the length of one side of the end plate (here, the length of the long side) and the number of tightening members disposed on this side. FIG. 3 is a graph showing the relationship between the length of one side of the end plate (here, the length of the short side) and the number of tightening members disposed on this side. In the graph of FIG. 2 and the graph of FIG. 3, the horizontal axis represents the length x (mm) of one side, and the vertical axis represents the number y of clamping members.

As shown in the graphs of FIG. 2 and FIG. 1 to No. Focusing on 3, it can be said that the length x of one side and the number y of clamping members are correlated.
As for the long side, sample no. 1 to No. When an approximate line with an order of 1 is determined by Microsoft Excel using 3., y = 0.0024x + 0.22. If it is a value of the area | region of the upper side than this approximation line as shown in FIG. 2, it can be said that an end plate does not deform | transform excessively. Sample No. 1 for which the evaluation is VG. 4 to No. Sample No. 10 out of 10. Focusing on 4, 5, and 7, although it can be said that the length x of one side and the number y of the fastening members are correlated, when an approximate line is similarly obtained, y = 0.00333x. As shown in FIG. 2, it can be said that the end plate is more difficult to deform if it is the value of the region above the approximate line.
As for the short side, sample no. 1 to No. Similarly, when the approximate line is determined using 3 and y = 0.0026x + 0.21, it can be said that the end plate is unlikely to be deformed excessively if the value is in the region above the approximate line. Sample No. 4 to No. Focusing on 10, these samples all have values in the region above y = 0.00333x. Also, for sample no. Similar approximation lines were obtained using 5, 9 and found to be y = 0.00333x + 0.33.
From the above, by averaging the inclination 0.0024 on the long side and the inclination 0.0026 on the short side and ignoring the y-intercept, the end plate deforms excessively by y = 0.0025x It can be said that it is rational to adopt it as a difficult boundary equation. In addition, it can be said that it is rational to adopt y = 0.00333x as the boundary equation in which the end plate is more difficult to deform. In the graphs of FIGS. 1 to 3, y = 0.0025x is indicated by a solid line, and y = 0.00333x is indicated by an alternate long and short dash line.

With reference to the above-mentioned boundary equation y = 0.0025x, y = 00. 1 to No. In each case 10, the values of 0.0025x and 0.00333x in Table 1 are compared with the number y of the tightening members, or as shown in the graphs of FIG. 2 and FIG. Since the number y is 0.0025x or more (0.0025x ≦ y), it is considered that the maximum deflection is small when the above-described hydraulic pressure or the like is received. Also, for sample no. 4 to No. In each case 10, it is considered that the maximum deflection is smaller because the number y of the fastening members is 0.00333x or more (0.00333x ≦ y). On the other hand, for sample no. 101 to No. In all cases, since the number y of clamping members is less than 0.0025x (y <0.0025x), the maximum deflection is greater than that of sample No. 1 to No. Considered greater than ten.

In addition, since the short side of the end plate is shorter than the long side (H <L), it tends to be difficult to deform. Therefore, if 0.0025x ≦ yl is satisfied for at least the long side of the long side and the short side of the end plate, it is considered that bending hardly occurs when receiving the above-described hydraulic pressure or the like. In this test, although the number ys of fastening members disposed on the short side of the end plate is equal to or less than the number y1 of fastening members disposed on the long side, 0.0025x ≦ ys is satisfied. From this point as well, sample no. 1 to No. The short side of the 10 end plates is considered to be difficult to deform. In addition, it is expected that the rise of the internal pressure can be more easily reduced as described later if the number y1 of the tightening members on the long side is smaller than the number ys of the tightening members on the short side.

[Test Example 2]
Regarding the end plate provided in the cell stack and the RF battery described above, the length of one side and the number y of clamping members disposed on this side are variously changed to change the internal pressure of the battery cell due to the thermal expansion of the electrolyte. I checked the status.

In this test, when the battery cell stack is sandwiched between end plates having long sides having a side length L (mm) shown in Table 2 and clamped using bolts and nuts as clamping members The amount of change in the internal pressure of the battery cell when the electrolytic solution (here, the aqueous solution) stored in the battery cell thermally expands is determined. Specifically, the battery cell has a cell frame (see the above-mentioned FIG. 6 and the like) including a bipolar plate and a frame as a component, the frame and its opening (window) have a rectangular shape, and the width of the frame h _f ) is uniform on both the long side and the short side. Then, the deformation (deflection δx) of the frame caused by the increase ΔP of the internal pressure of the battery cell due to the thermal expansion of the electrolyte is determined as follows using the deflection formula of the beam.

(conditions)
Number of bolts on the long side = Value shown in Table 2 Bolt placement condition Equalize the bolts on each of the long side and short side (see Fig. 5)
The size of the bolt and nut should be constant (eg M20 equivalent bolt)
Frame thickness (t _f below) = 5 mm
Frame width (h _f ) = 15 mm
Young's modulus E _f = 3 GPa of frame (here, the frame is made of polyvinyl chloride (PVC), and the Young's modulus of PVC is adopted)
Bulk modulus of water k = 2.16 GPa, coefficient of thermal expansion of water β = 210 × 10 ⁻⁶ / ° C.
Temperature change ΔT = 20 ° C

The increase ΔP in internal pressure when the temperature change ΔT = 20 ° C. is expressed as follows using the volume change ratio of the electrolytic solution (ΔV / V = β × ΔT).
ΔP = k × (ΔV / V) = k × β × ΔT = (2.16 × 10 ³ ) × (210 × 10 ⁻⁶ ) × 20 ≒ 9.07 MPa

The maximum deflection δmax of the long side of the frame due to the above-mentioned increase ΔP in internal pressure is expressed as follows. In the following equation, the distance between adjacent bolts is the beam length a _f , the frame thickness is the beam width t _f , the frame width is the beam height h _f , and the sectional moment is I _f It is assumed that (= ((t _f ) × (h _f ³ ) / 12).
_{δmax = 5 × ΔP × (t} f) × (a f 4) / (384 × E f × I f)
In the long side of the frame, the change ΔS in the area of the opening of the frame caused by the deflection δx of the frame at a point of x (mm) along the longitudinal direction from the end is expressed as follows Ru. The area S of the opening of the frame is determined by (length of long side of frame-width of frame h _f × 2) x (length of short side-width of frame h _f × 2).
δx = [5 × ΔP × (t _f ) × x / (24 × E _f × I _f )] × [(a _f ³ ) −2 × (a _f ) × x ² + x ³ ]
ΔS = [∫ _{0 → af} (δx) dx] × [(number of tightening members on one side−1) × 2]
= [ΔP x (t _f ) x (a _f ⁵ ) / (120 x E _f x I _f )] x [(number of tightening members on one side-1) x 2]
The area S (mm ² ) of the opening, the second moment of area I _f , the increase in internal pressure ΔP (MPa), and the area change ΔS of the opening are shown in Table 2.

When the above-mentioned increase ΔP in internal pressure occurs, if the frame is elastically deformed, the subsequent internal pressure Pi is reduced. Since the change ΔS in the area of the opening described above is proportional to the change ΔV in the volume of the electrolyte (ΔS∝ΔV), the internal pressure Pi after the elastic deformation described above is expressed as follows. In addition, when the internal pressure Pi becomes a negative value by the following calculation, it is referred to as 0 MPa. The area ratio ΔS / S of the opening and the internal pressure Pi (MPa) are shown in Table 2.
Pi = ΔP-k × (ΔS / S)

(Evaluation judgment)
When the increase in internal pressure ΔP described above occurs, the frame elastically deforms, and the smaller the internal pressure Pi that exists thereafter, the smaller the internal pressure of the battery cell, even if the electrolytic solution in the battery cell is thermally expanded due to a temperature change. It can be said that the increase is small. Here, when the above-mentioned internal pressure Pi exceeds 1 MPa, the increase in internal pressure is large and it is evaluated as B because the internal pressure tends to rise. When the internal pressure Pi exceeds 0 MPa and is 1 MPa or less, the increase in internal pressure is small, and it is evaluated as G because the internal pressure is difficult to increase. The case where the internal pressure Pi is substantially 0 MPa is evaluated as VG as the internal pressure does not substantially increase. The results are shown in Table 2.

As shown in Table 2, sample nos. 11 to No. In all cases 20, the value of internal pressure Pi is small (here, 0.9 MPa or less), and the evaluation is G or VG. Even if the electrolyte stored in the battery cell thermally expands due to temperature change, it is restrained by the end plate It can be seen that the internal pressure of the battery cell does not easily rise, preferably does not substantially rise. Sample No. 16 to No. 20 shows that the value of the internal pressure Pi is smaller (here, 0 MPa), and substantially no increase in internal pressure due to the above-described thermal expansion of the electrolyte occurs. On the other hand, for sample no. 105-No. In all cases, the value of the internal pressure Pi is large (in this case, 5.2 MPa or more). 11 to No. It is understood that the above-mentioned increase in internal pressure is more likely to occur than 20.

Sample No. 11 to No. The value of the internal pressure Pi of 20 is small. 105-No. The reason why the value of the internal pressure Pi of 109 is larger is considered as follows. FIG. 4 is a graph showing the relationship between the length of one side of the end plate and the number of tightening members arranged on one side, where the horizontal axis is the length x (mm) of one side, and the vertical axis is the tightening member Indicates the number y of As shown in the graph of FIG. 11 to No. Sample No. 15 with an evaluation of B; 105-No. Focusing on 109, it can be said that the length x of one side and the number y of the fastening members are correlated. Therefore, when an approximate line having an order of 1 was determined by Microsoft Excel, sample No. 1 was obtained. 11 to No. The approximate line of 15 is y = 0.0116x + 5.71. Sample No. 105-No. The approximate line of 109 is y = 0.0172x + 4.35. The average of the slopes of these two approximate lines and the average of the y-intercept are determined. The approximation line using the average value is y = 0.014x + 5. It can be said that it is rational to adopt this equation y = 0.014x + 5 as the equation of the boundary where the internal pressure of the battery cell is hard to rise. Similarly, for sample no. 16 to No. The approximate line of 20 is y = 0.0102x + 4.19. Using the slope of y = 0.0116x + 5.71 and the y-intercept of y = 0.0102x + 4.19, the equation y = 0.012x + 4 is obtained. It can be said that it is rational to adopt this equation y = 0.012x + 4 as the equation of the boundary where the internal pressure of the battery cell is more difficult to increase. In the graphs of FIG. 1 and FIG. 4, y = 0.014x + 5 is indicated by a solid line, and y = 0.012x + 4 is indicated by a two-dot chain line.

With reference to the boundary equation y = 0.014x + 5, y = 0.012x + 4 described above, sample no. 11 to No. In each case 20, the number y of clamping members is as shown by comparing the value of 0.014x + 5 or the value of 0.012x + 4 in Table 2 with the number y of clamping members or as shown in the graph of FIG. It is 0.014x + 5 or less (y <= 0.014x + 5). Therefore, the cell frame (frame) can be elastically deformed even if the electrolytic solution in the battery cell thermally expands due to a temperature change when the RF battery is stopped in a state where the electrolytic solution is stored in the battery cell. This elastic deformation can alleviate the pressing force applied to the frame due to the thermal expansion, and is considered to be easy to reduce the rise in the internal pressure of the battery cell. Also, for sample no. 16 to No. In each case 20, since the number y of the fastening members is 0.012x + 4 or less (y ≦ 0.012x + 4), it is considered that the rise in the internal pressure of the battery cell can be further easily reduced. On the other hand, for sample no. 105-No. In each case, since the number y of tightening members exceeds 0.014x + 5 (0.014x + 5 <y), sample No. 11 to No. It is considered that the internal pressure of the battery cell is more likely to rise than 20. For these sample nos. 105-No. At 109, it is considered that the cell frame, particularly the frame, may cause breakage of the battery cell components such as cracking or cracking.

In this test, the long side of the end plate and the frame of the cell frame is shown, but the same applies to the short side.

By combining the results of Test Examples 1 and 2, when the length x of one side of the end plate is in the range of 500 mm or more and 1600 mm or less, the number y of clamping members disposed on this side is 0.0025 x ≦ y ≦ 0. It has been shown that if 014x + 5 is satisfied, it is possible to construct a cell stack or an RF battery in which the internal pressure of the battery cell is difficult to increase due to thermal expansion of the electrolyte while suppressing excessive deformation of the end plate. In addition, from this result, when the number y of the tightening members satisfies 0.0025x ≦ y ≦ 0.014x + 5 in the range where the length x is 100 mm or more and 2000 mm or less, excessive deformation of the end plate is similarly obtained. While suppressing, it is expected that it can be set as a cell stack and RF battery which are hard to increase the internal pressure of a battery cell due to the thermal expansion of electrolyte solution.

The present invention is not limited to these exemplifications, is shown by the claims, and is intended to include all modifications within the scope and meaning equivalent to the claims.

10 redox flow battery (RF battery)
DESCRIPTION OF SYMBOLS 10C battery cell 100 laminated body 11 diaphragm 14 positive electrode 15 negative electrode 16 negative electrode tank 17 negative electrode tank 160,170 pump 162,164,172,174 Piping 18 seal material 20 cell frame 21 bipolar plate 22 frame 22 frame 22 w window part 24i, 25i Liquid supply hole 24o, 25o Drain hole 26i, 26o, 27i, 27o Slit 30 Cell stack 32 End plate 32o Outer edge 33, a to e, A to D Fastening member 330 bolt 332 Nut 35 Outer region 400 AC / DC conversion Transformer 410 substation equipment 420 generator 440 load

Claims (5)

A laminate in which a plurality of redox flow battery cells are laminated;
A pair of end plates sandwiching the laminate;
And a plurality of clamping members disposed in outer edge regions of both end plates and clamping between the two end plates,
The end plate has a rectangular planar shape,
The length x of one side of the rectangle is 100 mm or more and 2000 mm or less,
The number y of the clamping members arranged on one side of the rectangle is
A cell stack which is a natural number that satisfies 0.0025x ≦ y ≦ 0.014x + 5. The cell stack according to claim 1, wherein the number of the fastening members disposed on the long side of the rectangle is equal to or more than the number of the fastening members disposed on the short side of the rectangle. The cell stack according to claim 1, wherein the number y of the fastening members satisfies 0.00333 x ≦ y. The cell stack according to any one of claims 1 to 3, wherein the number y of the fastening members satisfies y ≦ 0.012x + 4. A redox flow battery comprising the cell stack according to any one of claims 1 to 4.

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