JP2015122231A - Redox flow cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a redox flow cell excellent in overall energy efficiency.SOLUTION: A redox flow cell including a barrier membrane, a bipolar plate, and an electrode arranged between the barrier membrane and the bipolar plate circulates electrolyte through the electrode to perform charge/discharge. The bipolar plate includes a flow channel through which the electrolyte flows on an electrode side surface. The electrode includes an electrode layer of which permeability K is 7.0×10mor more and 9.1×10mor less. The flow channel preferably comprises an introduction path through which the electrolyte is introduced into the electrode, and an exhaust path through which the electrolyte is exhausted from the electrode, and the introduction path and the exhaust path are independent without communicating with each other.

Description

  The present invention relates to a redox flow battery. In particular, the present invention relates to a redox flow battery that is excellent in overall energy efficiency by reducing the pressure loss of the electrolyte in an electrolyte flow type redox flow battery.

  Recently, as a countermeasure against global warming, power generation using natural energy (so-called renewable energy) such as solar power generation and wind power generation has been actively performed worldwide. These power generation outputs greatly depend on natural conditions such as the weather. Therefore, when the proportion of the power derived from natural energy in all the generated power increases, a problem in operating the power system, for example, a problem that it becomes difficult to maintain the frequency and voltage is predicted. One solution to this problem is to install large-capacity storage batteries to smooth output fluctuations, store surplus power, and level load.

  One of the large-capacity storage batteries is a redox flow battery (hereinafter sometimes referred to as an RF battery). An RF battery is a secondary battery that includes a diaphragm, a bipolar plate, and an electrode disposed between the diaphragm and the bipolar plate, and performs charging / discharging by circulating an electrolyte through the electrode. The electrolyte solution for an RF battery used for such an RF battery usually uses a metal ion whose valence changes by oxidation-reduction as an active material.

  The RF battery is required to have a low internal resistance and a small pressure loss when the electrolyte is permeated through the electrode. This is to increase the energy efficiency of the entire RF battery. For example, in order to reduce internal resistance, use of an electrode obtained by compressing a fibrous electrode material (hereinafter referred to as a compressed electrode) has been studied. However, depending on the electrode, the resistance (hereinafter referred to as the permeation resistance) when the electrolyte is circulated through the electrode may increase. That is, an electrode having a small transmittance represented by the reciprocal of the permeation resistance has a large pressure loss when the electrolyte is circulated. Therefore, in order to keep the flow rate of the electrolyte within a certain level within the electrode, it is necessary to increase the power of the pump, and the energy efficiency of the entire RF battery may be reduced.

  As a technique for solving such a problem, for example, an RF battery described in Patent Document 1 is cited. The RF battery described in Patent Document 1 includes an electrode composed of two layers of porous electrodes. And by making the surface area of the carbon fiber constituting the porous electrode on the diaphragm side larger than the surface area of the carbon fiber constituting the porous electrode on the bipolar plate side, it is possible to reduce the internal resistance and the permeation resistance, respectively. It is said that an RF battery with improved energy efficiency can be provided.

  Moreover, there exists a technique of patent document 2 as another technique for solving such a problem. In the RF battery described in Patent Document 2, a liquid permeable porous electrode having an A layer and a B layer made of different materials, wherein a groove is formed in the A layer disposed on the bipolar plate side. Is provided. And by arranging B layer toward the diaphragm side, it is said that an internal resistance and a permeation resistance can be reduced, and by extension, an RF battery with improved overall energy efficiency can be provided.

JP-A-8-287938 JP-A-9-245805

  With the future expansion of the use of RF batteries, there is a need for RF batteries that are further excellent in overall energy efficiency. Although the RF batteries described in Patent Document 1 and Patent Document 2 described above are excellent in energy efficiency as a whole RF battery to some extent, there is room for further improvement.

  Accordingly, one of the objects of the present invention is to provide an RF battery having excellent overall energy efficiency.

The redox flow battery of the present invention is a redox flow battery including a diaphragm, a bipolar plate, and an electrode disposed between the diaphragm and the bipolar plate, and charging / discharging by passing an electrolyte through the electrode. The bipolar plate has a flow path through which the electrolytic solution flows on the surface on the electrode side, and the transmittance K of the electrode is 7.0 × 10 ⁻¹⁴ m ² or more and 9.1 × 10 ⁻¹⁰ m. ² or less.

  According to the RF battery of the present invention, the pressure loss of the electrolytic solution can be reduced, and as a result, the overall energy efficiency is excellent.

It is a schematic front view showing the meshing type | mold opposing comb-tooth shaped flow path provided in the bipolar plate with which the RF battery which concerns on embodiment is equipped. It is a schematic sectional drawing showing the flow of the electrolyte solution in the meshing type | mold opposing comb-tooth shaped flow path provided in the bipolar plate with which the RF battery which concerns on embodiment is equipped. It is a schematic front view showing the non-meshing type opposing comb-tooth shaped flow path provided in the bipolar plate with which the RF battery which concerns on embodiment is equipped. It is a schematic front view showing the grid-shaped flow path provided in the bipolar plate with which the RF battery which concerns on embodiment is equipped. It is a schematic front view showing the meandering type flow path provided in the bipolar plate with which the RF battery which concerns on embodiment is equipped. It is a schematic front view showing the intermittent flow path provided in the bipolar plate with which the RF battery which concerns on embodiment is equipped. It is a schematic side view showing one form of the electrode with which the RF battery concerning an embodiment is provided. It is a schematic block diagram of the pressure loss measurement system used for the measurement of the transmittance | permeability. 1 is a schematic principle diagram of an RF battery according to an embodiment. It is a schematic block diagram of the cell stack with which the RF battery which concerns on embodiment is provided.

[Description of Embodiment of the Present Invention]
In order to increase energy efficiency, the present inventors have studied a method for reducing the pressure loss of the electrolytic solution. As a result, it was found that the pressure loss of the electrolytic solution can be reduced by providing a flow path through which the electrolytic solution flows on the electrode side surface of the bipolar plate. It has also been found that when an electrode provided with an electrode layer having a transmittance K in a certain range is used, the pressure loss of the electrolytic solution can be significantly reduced. The present invention has been made based on these findings. The contents of the embodiments of the present invention will be listed and described below.

(1) The RF battery according to the embodiment includes a diaphragm, a bipolar plate, and an electrode disposed between the diaphragm and the bipolar plate, and performs a charge / discharge reaction by circulating an electrolyte through the electrode. The bipolar plate has a flow path through which an electrolyte flows on the surface on the electrode side. The electrode includes an electrode layer having a transmittance K of 7.0 × 10 ⁻¹⁴ m ² or more and 9.1 × 10 ⁻¹⁰ m ² or less.

  By using a bipolar plate having a flow path, the pressure loss of the electrolyte can be reduced. This is because the flow of the electrolytic solution along the flow channel is promoted by the flow channel as compared with the case without the flow channel, and as a result, the flow of the electrolytic solution circulated through the electrode can be adjusted. In particular, in an electrode including an electrode layer having a transmittance K in the above range, the pressure loss of the electrolytic solution can be greatly reduced. From the above, the RF battery of the present embodiment is excellent in energy efficiency as a whole by reducing the pressure loss of the electrolytic solution.

(2) As RF battery of embodiment, the said flow path is provided with the introduction path which introduces the said electrolyte solution into the said electrode, and the discharge path which discharges the said electrolyte solution from the said electrode, The said introduction path and the said discharge path And are independent of each other.

  When the flow path has the above-described configuration, it is easy to reduce the pressure loss of the electrolyte. In addition, since the introduction path and the discharge path are not in communication and are independent, the electrolyte easily flows through the electrodes so as to cross between the introduction path and the discharge path. As a result, the amount of current increases due to a decrease in the electrolyte that is discharged without being reacted. From the above, the RF battery of this embodiment is excellent in energy efficiency as a whole.

(3) In the embodiment of the above (2), the introduction path and the discharge path each include a comb-shaped area, and the introduction path and the discharge path are meshed with each other. Are arranged so as to face each other.

  When the flow path has the above configuration, an increase in the pressure loss of the electrolytic solution can be further reduced. In addition, the introduction path and the discharge path are arranged so that the respective comb-shaped regions are engaged with each other so as to face each other, so that the electrodes pass between the respective comb teeth of the introduction path and the discharge path. The amount of electrolyte to be further increased. As a result, the amount of current further increases due to a decrease in the amount of electrolyte discharged without being reacted. From the above, the RF battery of this embodiment is excellent in energy efficiency as a whole.

(4) The RF battery of the embodiment includes a form in which the electrode layer includes a fine fiber layer mainly composed of fine fibers having a diameter of 0.005 μm to 1 μm.

  An electrode including a fine fiber layer has a high cell reactivity because of its large surface area if the transmittance is the same. Therefore, by using an electrode including a fine fiber layer, an RF battery having excellent energy efficiency as a whole can be obtained. Further, the fine fiber layer may be compressed at a high density in order to further increase the battery reactivity. In such a case, the transmittance K of the fine fiber layer becomes small, and as a result, the pressure loss of the electrolytic solution may be greatly increased. However, if a bipolar plate having a flow path is used, the pressure loss of the electrolyte can be reduced by adjusting the flow of the electrolyte flowing through the electrode. Therefore, the RF battery of this embodiment is excellent in energy efficiency as a whole.

(5) The RF battery of the embodiment includes a form in which the thickness of the electrode is 1000 μm or less in a state where the electrode is disposed between the diaphragm and the bipolar plate.

  When the electrode thickness is 1000 μm or less, the internal resistance can be further reduced. In addition, when the electrode is thin, the pressure loss of the electrolyte may increase significantly. However, if a bipolar plate having a flow path is used, the flow of the electrolyte can be adjusted, so that the pressure loss of the electrolyte can be reduced. . Therefore, the RF battery of this embodiment is excellent in energy efficiency as a whole.

[Details of the embodiment of the present invention]
Hereinafter, with reference to the drawings, the RF battery of the embodiment, and the electrodes and bipolar plates included in the RF battery of the embodiment will be described. The present invention is not limited to these embodiments, is shown by the scope of the claims, and is intended to include all modifications within the meaning and scope equivalent to the scope of the claims. Moreover, the same code | symbol shows the same name thing in a figure.

  The RF battery 1 according to the embodiment will be described with reference to FIG. The RF battery 1 according to the present embodiment typically includes a power generation unit 400 (for example, a solar power generation device, a wind power generation device, other general power plants, etc.) via an AC / DC converter 300 and a substation facility 310. ) And the load 500. Then, the power generated by the power generation unit 400 is charged and stored, or the stored power is discharged and supplied to the load 500. Here, the RF battery 1 is a V-type RF battery using vanadium (V) ions as an active material contained in the electrolytic solution. The RF battery 1 includes a cell stack (not shown) formed by laminating a plurality of battery cells 100, and a circulation mechanism (tanks 106 and 107, conduits 108 to 108) for supplying an electrolytic solution to the plurality of battery cells 100. 111, pumps 112, 113). The battery cell 100 includes a positive electrode cell 102 incorporating a positive electrode 104, a negative electrode cell 103 incorporating a negative electrode 105, and a diaphragm 101 that separates both the cells 102 and 103 and transmits ions. The RF battery 1 performs charging / discharging by circulating the electrolyte solution through the circulation mechanism to the electrodes 104 and 105 in the battery cell 100.

  As shown in FIG. 10, a cell frame 120 including a bipolar plate 121 integrated with a frame-like frame body 122 is used for the cell stack 200. The frame body 122 is provided on the outer periphery of the bipolar plate 121 on which the electrodes 104 and 105 are arranged on the front and back sides. The cell stack 200 has a structure in which a cell frame 120, a positive electrode 104, a diaphragm 101, a negative electrode 105, a cell frame 120,.

  The electrolyte solution is circulated by the supply manifolds 123 and 124 formed in the frame 122 and the drainage manifolds 125 and 126. The positive electrode electrolyte is supplied from the liquid supply manifold 123 to the positive electrode 104 via a groove formed on one surface side (the front side of the paper surface) of the frame body 122, and via the groove formed on the upper portion of the frame body 122. The liquid is discharged to the drainage manifold 125. Similarly, the negative electrode electrolyte is supplied from the liquid supply manifold 124 to the negative electrode 105 through a groove formed on the other surface side (the back side of the paper) of the frame 122, and is formed on the upper portion of the frame 122. The liquid is discharged to the drainage manifold 126 through the groove.

  The main features of the RF battery according to Embodiment 1 are that the bipolar plate 121 has a flow path for an electrolyte solution, and an electrode α (see FIGS. 7 and 10) that has an electrode layer with a predetermined transmittance. It is in use. Hereinafter, the bipolar plate 121 and the electrode α will be mainly described, and detailed description of the other components will be omitted.

(Bipolar plate)
The bipolar plate 121 will be described with reference to FIGS. The solid line arrows in each figure mainly indicate the flow of the electrolytic solution along the flow path 130 provided in the bipolar plate 121, and the broken line arrows indicate the flow of the electrolytic solution through the electrodes. The bipolar plate 121 is a plate that partitions each battery cell 100 and is formed of a conductive plate that allows current to pass but does not allow electrolyte to pass. The bipolar plate 121 of the present embodiment has a flow path 130 through which the electrolyte flows on the surface provided with the electrode α (see FIGS. 7 and 10), that is, on both surfaces thereof.

(Flow path)
The flow path 130 is provided in order to adjust the flow in each cell of the electrolyte solution which distribute | circulates to each electrode with a pump. The channel 130 is typically a groove. Thereby, as will be described later, the flow of the electrolyte flowing through each electrode is adjusted, and the pressure loss of the electrolyte can be reduced.

  The flow path 130 should just be a shape which can reduce the pressure loss of the electrolyte solution distribute | circulated. In particular, a shape that allows the electrolyte solution to flow uniformly over a wide range of the electrode α is preferable. Hereinafter, the shape of the flow path 130 will be described with an example.

(Non-communication shape)
The non-communication shape will be described with reference to FIGS. In FIGS. 1 and 3, the vertical direction of the drawing is the length, and the horizontal direction of the drawing is the width. As shown in FIGS. 1 and 3, the non-communication-shaped flow path 130 includes an introduction path 131 connected to the liquid supply manifold 123 (124) for introducing the electrolytic solution into each electrode, and the electrolytic solution from each electrode. And a discharge passage 132 connected to the drainage manifold 125 (126) for discharging. The introduction path 131 and the discharge path 132 are not in communication and are independent.

(Opposite comb shape)
The counter comb shape shown in FIG. 1 is an example of a non-communication shape, and the introduction path 131 and the discharge path 132 are each provided with a comb-shaped region, and the respective comb-shaped regions are engaged with each other and face each other. It is a mesh type opposed comb tooth shape arranged in this way. More specifically, the introduction path 131 (discharge path 132) is provided in the lower part (upper part) of the bipolar plate 121, and extends in the width direction from one horizontal groove 131a (132a), and upward (downward) from the horizontal groove. And a plurality of vertical grooves 131b (132b). And the introduction path 131 and the discharge path 132 are arrange | positioned so that the vertical groove 131b with which each is provided, and the vertical groove 132b mesh.

  With reference to FIG. 2, the flow of the electrolytic solution in the mesh type opposed comb tooth shape will be described. In FIG. 2, the vertical direction of the drawing is the thickness, and the horizontal direction of the drawing is the width. The mesh type opposed comb-tooth shape is such that when the electrolytic solution introduced from the introduction path 131 flows through the electrodes 104 and 105 to the discharge path 132, the longitudinal grooves 131b and the longitudinal grooves 132b in the electrodes 104 and 105 are formed. (Hereinafter, in FIG. 1 and FIG. 2), a flow across the width direction via a portion located between the two (hereinafter, a portion sandwiched between the vertical grooves 131b (132b) or the horizontal grooves 131a (132a) is collectively referred to as a flange). This is easy to form. As a result, not only the electrolyte flowing through the portions of the electrodes 104 and 105 facing the flow path 130 but also the electrolyte flowing through the collar contributes to the battery reaction, so that the electrolyte discharged without being reacted is reduced. To do. This is the same in any shape described later. Therefore, the amount of current of the RF battery increases, and as a result, the internal resistance of the RF battery can be reduced. Thereby, the energy efficiency as the whole RF battery can be improved.

  In the mesh type opposed comb shape, the length of the portion where the vertical groove 131b and the vertical groove 132b mesh is preferably as long as possible. This is because it can be expected that the amount of the electrolyte flowing across the buttock will increase, and a reduction in the internal resistance of the RF battery 1 due to the increase in the current amount can be expected. More specifically, the length of the portion where the vertical groove 131b and the vertical groove 132b mesh with each other is preferably 80% or more of the length direction of the bipolar plate 121, and more preferably 90% or more. .

  The mesh-type opposed comb tooth shape is not limited to the above arrangement. For example, the introduction path 131 (discharge path 132) is provided on the left side (right side) of the bipolar plate 121, and extends in the length direction from one vertical groove 131b (132b) to the right direction from the vertical groove 131b (132b). (Left direction)) may be provided with a plurality of lateral grooves 131a (132a).

  As an example of another non-communication shape, the non-engagement type opposing comb-tooth shape shown in FIG. 3 is mentioned. The non-meshing opposing comb tooth shape is a shape in which the introduction path 131 and the discharge path 132 do not mesh with each other. Here, the introduction path 131 and the discharge path 132 have a point-symmetric shape, and one vertical groove 131b (132b) provided on the right side (left side) of the bipolar plate 121 and the left side from the vertical groove 131b (132b). The shape includes a plurality of lateral grooves 131a (132a) extending to the right side. The introduction path 131 (discharge path 132) may have a shape including a plurality of vertical grooves 131b (132b) and a single horizontal groove 131a (132a) on which the plurality of vertical grooves 131b (132b) stand. This shape is a shape in which the introduction path 131 and the discharge path 132 do not mesh with each other in the meshing type opposing comb tooth shape shown in FIG.

  Even in the non-engagement type opposed comb-teeth shape, the lengthwise direction is provided via a region (buttock) located between adjacent channels (lateral grooves 131a (132a) in FIG. 3) in the electrodes 104 and 105. It is easy to form a flow (see broken line arrows in FIG. 3). Thereby, not only the electrolyte solution which flows through the part which opposes the flow path 130 in each electrode 104,105 but the electrolyte solution which flows through a collar part contributes to a battery reaction. As a result, it is expected that the electrolyte discharged without reaction will decrease and the amount of current of the RF battery will increase.

(Communication shape)
Another shape of the channel 130 is a communication shape. The communication shape includes a region continuously connected to the liquid supply manifold 123 (124) and the drainage manifold 125 (126). Hereinafter, an example of the communication shape will be described with reference to FIGS. 4 and 5. In each figure, the vertical direction of the drawing is the length, and the horizontal direction of the drawing is the width.

(Grid shape)
An example of the communication shape is a grid shape. Examples of the grid shape include a vertical grid shape as shown in FIG. The vertical grid type shape includes a plurality of vertical grooves 130b extending in the length direction of the bipolar plate 121 and a pair of horizontal grooves 130a provided so as to connect the upper and lower ends of the vertical grooves 130b in series. Other grid type shapes include a horizontal grid type shape and a cross grid type shape. The horizontal grid shape includes a plurality of horizontal grooves 130a arranged in parallel in the width direction of the bipolar plate 121 and a pair of vertical grooves 130b provided on the left and right so as to connect the horizontal grooves 130a in series. The cross grid type shape includes a plurality of horizontal grooves 130a arranged in parallel in the width direction of the bipolar plate 121 and a plurality of vertical grooves 130b extending in the length direction of the bipolar plate 121 so as to intersect with the plurality of horizontal grooves 130a. The cross grid type shape may be a shape including a plurality of grooves arranged in parallel in the oblique direction of the bipolar plate 121 and a plurality of grooves arranged in parallel so as to intersect with the plurality of grooves.

(Meandering shape)
Another example of the communication shape is a meandering shape as shown in FIG. The meandering shape is a shape constituted by a plurality of vertical grooves 130b extending in the length direction of the bipolar plate 121 and a plurality of horizontal grooves 130a that alternately connect upper ends or lower ends of vertical grooves 130b adjacent to the left and right. . Of course, it is good also as a shape comprised by the some horizontal groove | channel 130a arranged in the width direction of the bipolar plate 121, and the some vertical groove | channel 130b which connects the left ends or right ends of the horizontal groove 130a which adjoins up and down alternately.

  Even in the communication shape, the electrodes 104 and 105 cross in the length direction through a region (a collar portion) located between adjacent flow paths (vertical grooves 130b in FIGS. 4 and 5). It is easy to form a flow (see broken line arrows in FIGS. 4 and 5). As a result, not only the electrolytic solution flowing in the flow path 130 but also the electrolytic solution flowing in the buttocks easily contributes to the battery reaction, so the amount of electrolyte discharged without being reacted is reduced and the current amount of the RF battery is increased. It is expected.

(Other shapes)
Each channel 130 exemplified above may be intermittently formed at least partially. For example, as shown in FIG. 6, the longitudinal grooves 131 b (132 b) constituting the meshing type opposing comb tooth shape shown in FIG. 1 may be formed intermittently (discontinuously). By doing in this way, electrolyte solution distribute | circulates through each electrode 104,105 so that not only the width direction collar part but the collar part between the longitudinal grooves 131b (132b) adjacent to a length direction may be crossed. Since it becomes easy (refer to the broken line arrow in FIG. 6), it is expected that the amount of reaction current increases. Of course, the lateral groove 131a (132a) may be formed intermittently, or only a part of the flow path 130 may be formed intermittently. Further, in the above-described communication shape, when all of the continuously connected regions are formed intermittently, the flow path 130 is not a communication shape but a non-communication shape.

(Other channel configurations)
The width per channel (groove) is preferably 0.10 mm or more and 10 mm or less. (1) It is possible to increase the flow rate of the electrolyte flowing through the region on the diaphragm side of the electrode, (2) The electrode is less likely to fall into the channel (groove), (3) Pressure loss of the electrolyte flowing through the channel It is because the effect that it can reduce more is expectable. A more preferable width of the flow path is 0.2 mm or more and 2 mm or less, and a more preferable width of the flow path is 0.5 mm or more and 1.5 mm or less.

  The depth of the channel (groove) is preferably 50% or more and 99% or less of the thickness of the bipolar plate. (1) It is possible to increase the flow rate of the electrolyte flowing through the region on the diaphragm side of the electrode, (2) The electrode is less likely to fall into the channel (groove), (3) Pressure loss of the electrolyte flowing through the channel This is because the effect that the mechanical strength of the bipolar plate can be sufficient even if the flow path is provided can be expected. A more preferable depth of the channel is 70% or more and 80% or less of the thickness of the bipolar plate. When grooves are provided on both surfaces of the bipolar plate as in this embodiment, the groove portions having the above-described depth can be formed on both surfaces of the bipolar plate by providing the groove portions at positions that do not overlap when viewed through the plane.

  The cross-sectional shape of the channel (groove) can be any shape. For example, shapes such as a rectangular shape and a semicircular shape can be mentioned. The rectangular shape and the semicircular shape are expected to be (1) easy to form (easily process) the flow path in the bipolar plate, and (2) low pressure loss of the electrolyte flowing through the flow path.

  Moreover, it is preferable to arrange | position a flow path so that the space | interval of a vertical groove or a horizontal groove may become the same. Furthermore, it is preferable that the interval between the adjacent vertical grooves 131b and 132b in the opposing comb shape is the same as the interval between the lateral grooves 131a (131b) facing the edge of the vertical groove 131b (132b). This is because it is expected that the distribution of the electrolyte flowing through the buttock becomes uniform and the internal resistance can be further reduced.

  The number of vertical grooves and horizontal grooves in each shape described above can be arbitrarily adjusted. For example, if the number of longitudinal grooves exceeds 10 in the above-described opposed comb-tooth shape, it is expected that the effect of reducing the pressure loss of the electrolyte flowing through the flow path is great.

(Material and manufacturing method)
As the material of the bipolar plate, a conductive material that allows current to pass but not electrolyte can be used. In addition, a material having acid resistance and moderate rigidity is more preferable. This is because the cross-sectional shape and dimensions of the flow path are difficult to change over a long period of time, and the effect of the flow path is easily maintained. An example of such a material is a conductive material containing carbon. More specifically, a conductive plastic formed from graphite and a polyolefin-based organic compound or a chlorinated organic compound can be used. Further, a conductive plastic in which a part of graphite is substituted with at least one of carbon black and diamond-like carbon may be used. Examples of the polyolefin organic compound include polyethylene, polypropylene, polybutene and the like. Examples of the chlorinated organic compound include vinyl chloride, chlorinated polyethylene, and chlorinated paraffin. By forming the bipolar plate from such a material, the electric resistance of the bipolar plate can be reduced and the acid resistance is excellent.

  The bipolar plate can be manufactured by molding the above material into a plate shape by a known method such as injection molding, press molding, or vacuum molding. At this time, if the flow path is formed simultaneously with the formation of the bipolar plate, the production efficiency of the bipolar plate is excellent. Alternatively, a bipolar plate without a flow path may be manufactured, and then the surface of the bipolar plate may be cut.

(electrode)
The electrode α used for each of the electrodes 104 and 105 provided in the RF battery of the present embodiment will be described with reference to FIG. In FIG. 7, the vertical direction of the drawing is the length, the horizontal direction of the drawing is the thickness, and the direction from the front to the back of the drawing is the width. The electrode α includes an electrode layer α1 having a transmittance K of 7.0 × 10 ⁻¹⁴ m ² or more and 9.1 × 10 ⁻¹⁰ m ² or less. Here, as shown in FIG. 7, the electrode α is a single-layer electrode composed of only the electrode layer α1. Here, the transmittance K is the reciprocal of the transmission resistance of the electrode layer α1, and is obtained by an equation represented by ΔP = (h / K) μ (Q / wd) (referred to as Darcy-Weissbach equation). Value. K is the transmittance (m ² ), ΔP is the pressure loss (Pa), Q is the flow rate of the fluid introduced to the electrode (m ³ / s), μ is the viscosity of the fluid to be circulated (Pa · s) , H is the length (m) of the electrode layer α1, w is the width (m) of the electrode layer α1, and d is the thickness (m) of the electrode layer α1 compressed in the cell stack 200, respectively. Show. When the electrode α is a laminated electrode in which two or more electrodes are stacked, each electrode layer is integrated as the electrode α, and therefore can be separated by peeling each other. The transmittance K is a value unique to the electrode layer regardless of the type of fluid, and is a constant that can be measured using, for example, a fluid (water or the like) whose viscosity is known.

  The transmittance K can be obtained from, for example, the pressure loss ΔP and the fluid flow rate Q using the pressure loss measurement system 600 shown in FIG. The pressure loss measurement system 600 includes a measurement cell 610, a fluid tank 620, a pump 640, a flow meter 650, a differential pressure meter 660, and a pipe 630 that connects these devices. The measurement cell 610 contains an electrode layer for which the transmittance K is to be obtained. The fluid tank 620 stores the fluid 622 introduced into the electrode layer. The pump 640 pumps the fluid 622 to each device via the pipe 630, and the flow meter 650 measures the flow rate of the fluid on the pump outlet side. The differential pressure gauge 660 is connected to the measurement cell 610 in parallel by a pipe 630 and measures the pressure loss ΔP. The measurement cell 610 includes a storage portion (not shown) for storing the electrode layer, and a spacer (not shown) for securing the thickness d of the electrode layer to 0.2 to 0.5 mm is disposed in the storage portion. Is done. The flow meter 650 and the differential pressure meter 660 are attached to the pipe 630. A one-dot chain line arrow in FIG. 8 indicates a direction in which the fluid 622 flows.

  An electrode layer having a length h of 100 mm and a width d of 50 mm is pushed into the storage cell 610. Then, a fluid 622 (water, where viscosity μ is a constant) is circulated by a pump 640 through a measurement cell 610 that holds an electrode layer. A fluid 622 is introduced into the electrode layer from its side surface (surface having a cross-sectional area wd) and is distributed in the length direction thereof. At this time, the pressure loss ΔP when the flow rate Q is changed to various values by adjusting the pump 640 is measured by the differential pressure gauge 660, respectively. Then, the flow rate Q is plotted on the horizontal axis and the pressure loss ΔP is plotted on the vertical axis. These plotted measurement points are approximated by the above Darcy-Weissbach equation, and the slope of the approximate line is defined as transmittance K.

  The electrode layer α1 having the transmittance K as described above has a relatively low transmittance K, and therefore, when combined with a bipolar plate without a flow path, the pressure loss of the electrolyte increases. In this regard, in the present embodiment, as described above, the flow of the electrolyte can be adjusted by providing a flow path (not shown) in the bipolar plate 121, so that the pressure loss can be reduced, and consequently the energy efficiency of the entire RF battery. Can be improved.

The transmittance K of the electrode layer α1 is 7.0 × 10 ⁻¹⁴ m ² or more and 9.1 × 10 ⁻¹⁰ m ² or less. When the transmittance K is in the above range, the pressure loss of the electrolytic solution can be greatly reduced. In particular, since the transmittance K is 7.0 × 10 ⁻¹⁴ m ² or more, the pressure loss can be set to a certain value or less (for example, 40 kPa or less) depending on the shape of the flow path. Excellent. Further, when the transmittance K is 9.1 × 10 ⁻¹⁰ m ² or less, it is expected that the internal resistance can be made a certain value or less by increasing the amount of reaction current, and consequently, the energy efficiency of the entire RF battery is excellent. The The transmittance K is preferably 1.4 × 10 ⁻¹⁰ m ² or less, and more preferably 7.1 × 10 ⁻¹¹ m ² or less. This is because it is expected that an RF battery in which pressure loss and internal resistance are reduced in a balanced manner can be obtained. The transmittance K can be adjusted by the compression rate, porosity, fiber diameter, and the like of the electrode layer α1.

  The thickness (d) of the electrode α can be arbitrarily adjusted by the structure of the cell stack. In particular, the thickness of each of the electrodes 104 and 105 is preferably 1000 μm or less in a state where the electrodes 104 and 105 are disposed between the diaphragm 101 and the bipolar plate. When the electrode α is thin, the pressure loss of the electrolytic solution may increase significantly. However, if the bipolar plate 121 having a flow path is used, the flow of the electrolytic solution can be adjusted, so that the pressure loss of the electrolytic solution can be reduced. Because. The thickness of the electrode α is more preferably 500 μm or less, further preferably 300 μm or less. As will be described later, the same applies to the case where each of the electrodes 104 and 105 is a laminated electrode including two or more electrode layers.

(Electrode layer)
Hereinafter, the electrode layer α1 included in the electrode α will be described with some examples. The electrode α may be a single-layer electrode using an electrode layer exemplified below alone, or may be a laminated electrode in which these electrode layers and other electrode layers are combined.

(Fine fiber layer)
The fine fiber layer is an electrode layer mainly composed of fine fibers having conductivity having an average diameter of 0.005 μm to 4 μm. If the fine fiber layer has the same transmittance K, the fine fiber layer has a larger surface area than the thick fiber layer described later, and thus has excellent battery reactivity. Here, the fine fiber layer may be compressed in order to further increase battery reactivity. In such a case, the transmittance K of the fine fiber layer may decrease, and the pressure loss of the electrolytic solution may increase. Even in such a case, by providing the bipolar plate 121 with the flow path as described above, the pressure loss can be reduced, and the energy efficiency of the entire RF battery can be improved. The average diameter of the fine fibers is more preferably 0.1 μm or more and 1.0 μm or less, and further preferably 0.1 μm or more and 0.3 μm or less. An average diameter can be calculated | required by averaging the result measured 5 or more points | pieces per 1 visual field under a microscope. The same applies to the thick fiber layer described later.

  The fine fiber layer preferably has a certain porosity or more. This is because if the porosity of the fine fiber layer is low, the flow of the electrolytic solution in the stacking direction of the bipolar plate and the diaphragm and the ion conduction through protons in the electrolytic solution are hindered. Therefore, the porosity of the fine fiber layer is preferably 80% or more and 99.9% or less. The porosity of the fine fiber layer is more preferably 85% to 95%, and still more preferably 88% to 95%. The porosity can be determined from the apparent volume and the true volume of the fine fiber layer. The apparent volume is the volume of the entire thin fiber layer in a compressed state and includes a void. The true volume is a value obtained from the specific gravity and mass of fine fibers, and is the volume of fine fibers that do not include voids. The same applies to the thick fiber layer described later.

  The characteristics required for the fine fiber material are to have electrical conductivity and to cause a battery reaction with the electrolytic solution. A typical example of a material that satisfies such characteristics is carbon. In addition, a metal fiber or the like on which a catalyst is supported can be used as a fine fiber material.

  The fine fiber layer can be produced by using a solid phase method or a liquid phase method. For example, a template carbonization method, an electrospinning method, a melt-blow method, or the like can be used. These techniques are suitable for forming a fine fiber layer composed of fine fibers satisfying the above-mentioned average diameter and satisfying the above-mentioned porosity. After the fine fiber layer is formed, the fine fiber layer is preferably subjected to flameproofing treatment and carbonization treatment.

(Thick fiber layer)
The thick fiber layer is an electrode layer mainly composed of thick fibers having an average diameter of 5 μm or more and 20 μm or less. The thick fiber layer is stronger and stronger than the fine fiber layer. In addition, the electrode α, whose predetermined strength is guaranteed by the thick fiber layer, is difficult to damage when transported to the battery production site or cut into a desired shape, contributing to the improvement of RF battery productivity. Because it does.

  The average diameter of the thick fibers is preferably 5 μm or more and 20 μm or less. With such a thick fiber, the thick fiber layer can have strength as a base material. A preferable average diameter of the thick fibers is 7 μm or more and 12 μm or less, and a more preferable average diameter of the thick fibers is 7 μm or more and 10 μm or less.

  The thick fiber layer including the thick fibers having the above configuration preferably has a porosity of a certain level or more. This is because when the porosity of the thick fiber layer is low, the flow of the electrolytic solution in the stacking direction of the bipolar plate 121 and the diaphragm 101 and the ionic conduction via protons in the electrolytic solution are hindered. Therefore, the porosity of the thick fiber layer is preferably 60% or more and 90% or less. If the porosity is 60% or more, the flow of the electrolyte and the ionic conduction in the stacking direction become smooth. Moreover, if the porosity is 90% or less, the thick fiber layer can have sufficient strength to exhibit the function as a substrate. A more preferable porosity of the thick fiber layer is 70% or more and 90% or less, and a more preferable porosity of the thick fiber layer is 75% or more and 85% or less.

  Examples of the thick fiber layer that satisfies the above-described characteristics include carbon paper and carbon cloth. Carbon paper which is a composite material of carbon fiber and carbon has sufficient conductivity and tensile strength. A carbon cloth which is a woven or non-woven fabric of carbon fibers also has sufficient conductivity and tensile strength.

For example, the carbon paper containing fine fibers having an average diameter of 7 μm and having a porosity of 80% and an average thickness of 0.1 mm has a tensile strength of 3 kgf / cm ² (about 294 kPa). When the average thickness of the carbon is 0.4 mm, the tensile strength is 8 kgf / cm ² (about 785 kPa). The tensile strength of carbon paper having a porosity of 90% and an average thickness of 0.4 mm is 4 kgf / cm ² (about 392 kPa).

(Laminated electrode)
The electrode α may be any electrode provided with the electrode layer α1 whose transmittance K is the above value. Therefore, the electrode α is a laminated electrode obtained by laminating two or more electrode layers in addition to the electrode composed of only the electrode layer α1 having the transmittance K as described above, and at least one electrode The layer may be the electrode layer α1. When the electrode α is a laminated electrode, the number of electrode layers α1 having the transmittance K having the above value and the number of electrode layers other than the electrode layer α1 can be arbitrarily adjusted. In the laminated electrode, a plurality of electrode layers α1 may be used, and the transmittance K of each electrode layer α1 may be varied within the above range. The transmittance K1, K2,... Of each electrode layer can be adjusted by the compression rate, porosity, fiber diameter, etc. of each electrode layer.

  In the laminated electrode, the transmittance K1 of the electrode layer on the diaphragm side (diaphragm side layer) is preferably larger than the transmittance K2 of the layer on the bipolar plate side (bipolar plate side layer). It is easy to distribute most of the electrolyte solution (80% or more in some cases) distributed to the laminated electrode to the diaphragm side layer having a high transmittance K. As a result, if the electrode is a single-layer electrode, the flow rate of the electrolyte solution may be reduced, so that the electrolyte solution can be sufficiently passed through the region on the diaphragm side of the electrode, thereby increasing the amount of reaction current and reducing the internal resistance. Expected to be done. Further, for example, if the diaphragm side layer is made of an electrode material having high battery reactivity, it is expected that a large amount of electrolyte flows in the diaphragm side layer, thereby contributing to improvement of the output of the RF battery. In particular, it can be said that the transmittance K1 is sufficiently larger than the transmittance K2 when the transmittance K1 is 1.2 times or more, and further twice or more the transmittance K2. In this case, the flow rate of the electrolyte flowing through the region on the diaphragm side of the electrode is further increased, and the variation in the flow rate and flow rate of the electrolyte depending on the location of the electrode can be reduced, and the reaction efficiency of the electrolyte is expected to increase. The Further, when the transmittance K1 is 50 times or less of the transmittance K2, more preferably 20 times or less, and even more preferably 5 times or less, for example, in the case of including the above-described meshing type opposed comb-shaped flow path, etc. It is expected that the flow of the electrolyte solution between the introduction path and the discharge path is likely to occur uniformly regardless of the location of the electrode. Thereby, it is expected that the battery reaction is easily performed in a wide range of the electrode, and the internal resistance is reduced.

The electrode α is preferably used for the bipolar plate side layer, and more preferably an electrode layer having a transmittance larger than that of the bipolar plate side layer is used on the diaphragm side. In particular, when the flow path includes adjacent groove portions and groove portions, when the electrolytic solution flows in the electrode α between the adjacent groove portions, the electrolytic solution flows on the bipolar plate side in the electrode thickness direction. This is because it is possible to suppress this and make it easier for the electrolytic solution to flow on the diaphragm side. More specifically, by suppressing the flow of the electrolyte solution to the bipolar plate side in the electrode α, the electrolyte solution linearly crosses from one groove portion to the other groove portion without causing a battery reaction sufficiently. To suppress the flow. Along with this, the electrolyte once flows from one adjacent groove to the diaphragm side in the electrode α, the electrolyte flows along the diaphragm side in the parallel direction of the groove, and further from the diaphragm side toward the other groove. By flowing so as to cross, it is possible to form a bypass path of the bent electrolyte solution. It is considered that the flow of the electrolytic solution flowing in such a manner tends to make the flow rate of the electrolytic solution flowing through the electrodes uniform regardless of the location, thereby improving the reaction efficiency of the electrolytic solution and increasing the current density. The transmittance K2 of the bipolar plate side layer is more preferably 1.4 × 10 ⁻¹⁰ m ² or less, and still more preferably 7.1 × 10 ⁻¹¹ m ² or less. When the electrode layer α1 is used for the bipolar plate side layer, the transmittance K1 of the diaphragm side layer is 8.4 × 10 ⁻¹⁴ m ² or more and 4.5 × 10 ⁻⁸ m ² or less. It is expected to be easy to play. More preferable transmittance K1 is 8.4 × 10 ⁻¹³ m ² or more and 7.0 × 10 ⁻⁹ m ² or less, and further preferably 3.5 × 10 ⁻¹⁰ m ² or less.

  When the product of the transmittance K1 of the diaphragm side layer and the thickness d1 of the diaphragm side layer is K1d1, and the product of the transmittance K2 of the bipolar plate side layer and the thickness d2 of the bipolar plate side layer is K2d2, the ratio of these products Preferably, K1d1 / K2d2 is greater than 4. This is because it is easy to distribute most of the electrolyte solution (80% or more in some cases) distributed to the laminated electrode to the diaphragm side layer having a high transmittance K. As a result, if the electrode is a single-layer electrode, the flow rate of the electrolyte solution may be reduced, so that the electrolyte solution can be sufficiently passed through the region on the diaphragm side of the electrode, thereby increasing the amount of reaction current and reducing the internal resistance. Expected to be done. Further, for example, if the diaphragm side layer is made of an electrode material having high battery reactivity, it is expected that a large amount of electrolyte flows in the diaphragm side layer, thereby contributing to improvement of the output of the RF battery. A more preferable value of K1d1 / K2d2 is 4 or more and 20 or less. This is because in the case where the flow path includes the introduction path and the discharge path, a flow of the electrolyte solution that crosses between the introduction path and the discharge path is likely to occur uniformly regardless of the location of the electrode.

  Moreover, when the thickness d1 of the diaphragm side layer is 10 μm or more and 500 μm or less and the thickness d2 of the bipolar plate side layer is 10 μm or more and 500 μm or less, the flow rate of the electrolyte flowing through the region on the diaphragm side of the electrode is further increased. This is preferable because the current density can be increased. A more preferable thickness d1 is 100 μm or more and 400 μm or less, more preferably 200 μm or more and 400 μm or less, and particularly preferably 250 μm or more and 350 μm or less. Further, the more preferable thickness d2 is 100 μm or more and 400 μm or less, more preferably 200 μm or more and 400 μm or less, and particularly preferably 250 μm or more and 350 μm or less. Furthermore, the thickness d2 is preferably ½ or less, more preferably ¼ or less of the thickness d1. This is because the amount of the electrolyte flowing into the region where the flow rate of the electrolyte is small can be increased.

  When a laminated electrode is used as the electrode α, the thick fiber layer is preferably a bipolar plate side layer, and the fine fiber layer is preferably a diaphragm side layer. By making the fine fiber layer the main component of the battery reaction, and using the thick fiber layer that is stronger and stronger than the fine fiber layer as the base material, the electrode α is excellent in battery reactivity, and the electrode α is produced. It is because it can suppress that a fine fiber layer is damaged. Moreover, since the predetermined strength is guaranteed by the thick fiber layer, it is difficult to damage when transported to the RF battery production site or when it is cut into a desired shape, which contributes to the improvement of the productivity of the RF battery. . In such a case, the material of the thick fibers constituting the thick fiber layer may be a material that causes a battery reaction with the electrolytic solution, or may be a material that does not cause a battery reaction.

  Further, when forming the fine fiber layer into the thick fiber layer, the electrode α can be produced with high productivity by a roll-to-roll method if the solid phase method or the liquid phase method is used. Specifically, a thin fiber layer is formed on the surface of the thick fiber layer by a solid phase method or a liquid phase method in the middle of feeding the thick fiber layer wound around the first roll onto the second roll. The electrode α on which the fine fiber layer is formed is wound around a second roll. Here, the reason why the electrode α can be produced while winding the electrode α around the second roll is that the thick fiber layer mechanically protects the fine fiber layer and suppresses damage to the fine fiber layer.

<Analysis example 1>
[Flow velocity distribution and pressure loss]
In Analysis Example 1, the characteristics of the RF battery of this embodiment were examined. In this analysis example, a model 1 including a bipolar plate having meshed opposed comb-shaped channels shown in FIG. 1 was constructed using simulation analysis software (Ansys Fluent, manufactured by Ansys Japan Co., Ltd.). Model 1 is an RF battery having a single cell structure including one positive cell and one negative cell. At this time, the positive electrode and the negative electrode were single-layer electrodes having the same transmittance and shape. Moreover, in the model 1, as shown in FIG. 1, electrolyte solution is introduce | transduced from the lower part of a bipolar plate, and is discharged | emitted from the upper part. Therefore, as in the above embodiment, the vertical direction of the drawing is the length (Y direction), the horizontal direction of the drawing is the width (X direction), and the direction from the front of the drawing to the back side is the thickness (Z direction). Further, for comparison, a model 2 having the same configuration as that of the model 1 was constructed except that the bipolar plate does not have a flow path. In both models, when the transmittance K is various, (1) the flow rate distribution of the electrolyte in the electrodes in the X and Y directions (the electrolyte in the X direction relative to the flow rate of the electrolyte in the Y direction) (Hereinafter referred to as XY speed ratio), (2) The pressure loss obtained from the pressure distribution in the electrode was examined. Detailed analysis conditions are shown below.

<< Analysis conditions >>
(electrode)
Length: 15.8 (cm), Width: 15.8 (cm), Thickness: 0.05 (cm)
Electrode reaction area density (A): 50000 (l / m)
Electrode reaction rate constant (k): 3.0 × 10 ⁶ (m / s)
(Electrolyte)
Sulfuric acid V aqueous solution (V concentration: 1.7 mol / L, sulfuric acid concentration: 3.4 mol / L)
State of charge (sometimes referred to as state of charge): 50%
(Electrolyte flow rate, etc.)
Inlet flow rate: 150 (ml / min)
Outlet flow rate: Free outflow Flow model: Laminar flow model (Dipolar plate)
Height (Y direction) and width (X direction): 15.8 (cm), thickness: 0.12 (cm)
<Flow path>
Groove shape: meshing shape of opposing comb teeth Number of longitudinal grooves: 39 introduction paths x 40 discharge paths Vertical groove length: 21 (cm)
Groove width: 0.1 (cm)
Groove depth: 0.1 (cm)
Vertical groove interval: 0.1 (cm)
Groove cross section: square

[Internal resistance and energy loss]
Based on the analysis results of the flow velocity distribution and pressure loss by the above models 1 and 2, and the calculation program using the calculation method described in the following literature 1, the values when the transmittance K is various values in the above models 1 and 2 are satisfied. The internal resistance during discharge was determined. In the case of an RF battery having a single cell structure, the internal resistance is synonymous with the cell resistivity which is the resistivity per cell. Therefore, hereinafter, the internal resistance is represented by cell resistivity. The cell voltage for obtaining the cell resistivity was obtained by the calculation method described in Document 1 (details omitted). Further, the energy loss of the RF battery was determined from the obtained internal resistance (cell resistance) and the above analysis conditions. The calculation methods for internal resistance and energy loss described in Document 1 are shown below. In addition, each item in the following calculation method is also shown by an item premised on a single cell structure like the cell resistivity.
Reference 1 ... A. A. Shah et al. "A dynamic performance model for redox-flow butteries involving solving specifications", Electrochimica Acta 53 (2008), p. 8087-8100

(Cell resistivity (internal resistance))
Calculation method: R = (V1-V0) / I
R: Cell resistivity (Ω · cm ² )
I: Cell current density (A / cm ² )
V0: Cell voltage (V) at a cell current density of 0
V1: Cell voltage (V) at cell current density I (A / cm ² )

(Energy loss)
Calculation method: W = (QΔP) + (J ² R / S)
W: Energy loss (J / s)
Q: Inlet flow rate (m ³ / s)
ΔP: Pressure loss (Pa) between the cell inlet and the cell outlet
J: Cell current (A)
R: Cell resistivity (Ωcm ² )
S: Cell area (cm ² )

  Tables 1 and 2 show the values of the characteristics relating to the analysis results and calculation results of Model 1 (when a flow path is provided) and Model 2 (when a flow path is not provided), respectively. The XY speed ratio in Table 1 and Table 2 indicates the XY speed ratio at the center of the electrode where the speed in the X direction and the Y direction is the fastest. Table 3 shows the results of comparing the values of the characteristics of the electrodes having the same transmittance K in model 1 and model 2. The difference in XY speed ratio in Table 3 is obtained by subtracting the XY speed ratio of model 2 from the XY speed ratio of model 1. In addition, the comparison of cell resistivity, pressure loss, and energy loss in Table 3 shows that the value of each characteristic of model 1 is the value of each characteristic of model 2 when each value of model 2 is 100. %. Any numerical value of less than 100% indicates that the characteristics of model 1 are superior to that of model 2, and that of 100% or more indicates that characteristics of model 2 are superior to that of model 1. .

[result]
(Reduction of pressure loss)
According to Table 3, when the electrode transmittance K is 9.03 × 10 ⁻¹⁰ m ² or less, a bipolar plate having a flow path is used, and this occurs when a bipolar plate having no flow path is used. It can be seen that the pressure loss can be about 15% or less. Further, when the electrode transmittance K is reduced, by using a bipolar plate having a flow path, the pressure loss generated when a bipolar plate having no flow path is used is about 3% or less, and further about It can be seen that it can be 1% or less, particularly about 0.1% or less. Thus, it can be seen that by using a bipolar plate having a flow path, the pressure loss can be greatly reduced as compared with the case of using a bipolar plate not having a flow path.

(Cell resistivity)
From Table 3, when the transmittance K of the electrode α is 7.04 × 10 ⁻¹¹ m ² or less, a cell using a bipolar plate having no flow path is used by using a bipolar plate having a flow path. It can be made smaller than the resistivity. Further, it is understood that when the transmittance K of the electrode α is decreased, the cell resistivity can be reduced to about 90% when a bipolar plate having a flow path is used. . As shown in Table 3, this is considered to be caused by the fact that the XY speed ratio exceeds 1.0. That is, the amount of electrolyte that flows so as to cross the electrodes between the comb teeth of the introduction path and the discharge path (flows in the X direction) is reduced, so that the amount of electrolyte that is discharged unreacted decreases. This is probably because the amount of current is increasing. As described above, a low cell resistivity (internal resistance) is synonymous with a sufficient battery reaction at the electrode and a high amount of current.

From Table 3, when the transmittance K of the electrode α is 1.42 × 10 ⁻¹⁰ m ² , the cell resistivity is 112%, and the transmittance K is 9.03 × 10 ⁻¹⁰ m ^2. It can be seen that in this case, the cell resistance is 131%. If the electrode α has a transmittance K at which the cell resistivity is about 130% or less, the electrode α is a bipolar plate side layer, and an electrode having a higher transmittance than the electrode α is a diaphragm side layer. By using this laminated electrode, it is expected that the internal resistance can be reduced as compared with the RF battery using a bipolar plate not having a flow path and the electrode α as a single layer electrode. In the case where the bipolar plate is provided with a flow path, a cell having a two-layer structure in which the transmittance K1 of the diaphragm side layer is larger than the transmittance K2 of the bipolar plate side layer is used, compared with the case where a single layer electrode is used. This is because it is expected that the resistivity can be reduced.

(Reduction of energy loss)
From Table 3, it can be seen that when the electrode transmittance K is 7.04 × 10 ⁻¹¹ m ² or less, the energy loss can be reduced to about 85% or less when a bipolar plate without a flow path is used. Further, when the electrode transmittance K is reduced, the energy loss generated when a bipolar plate having a flow path is used is about 28% or less, further about 5% or less, especially 0.5% or less. It can be seen that. This is presumably because the pressure loss and the cell resistivity are greatly reduced as described above, compared to the case where a bipolar plate without a flow path is used. On the other hand, when the transmittance K of the electrode α is 1.42 × 10 ⁻¹⁰ m ² or more and 9.03 × 10 ⁻¹⁰ m ² or less, the energy loss that occurs when a bipolar plate that does not include a flow path is used. It can be seen that it is about 100% or more and 130% or less. Even in such a case, it is expected that the cell resistivity can be reduced as described above and the energy loss can be reduced by using the electrode α as the bipolar plate side layer of the laminated electrode having the two-layer structure.

Further, from Table 1 and Table 3, even when a bipolar plate having a flow path is used, if the electrode transmittance K is less than 7.04 × 10 ⁻¹⁴ m ² , energy loss increases. (See Analysis Examples 1-6 and 1-7). This is considered to be due to the fact that the pressure loss is large and the reduction in cell resistivity has almost reached its peak when the electrode transmittance K is 7.04 × 10 ⁻¹² m ² or less. It is done.

(Summary)
From the above, it can be seen that when the transmittance K of the electrode layer is 7 × 10 ⁻¹⁴ m ² or more and 9.1 × 10 ⁻¹⁰ m ² or less, the reduction in pressure loss due to the bipolar plate provided with the flow path is significant. . In particular, when the electrode is a single layer electrode, when the transmittance K is 7.0 × 10 ⁻¹⁴ m ² or more and 7.1 × 10 ⁻¹⁰ m ² or less, the internal resistance (cell resistivity) is reduced. Since the reduction is significant, it can be seen that the RF battery as a whole is excellent in energy efficiency. Further, when a laminated electrode having a two-layer structure in which an electrode is a bipolar plate side layer and an electrode having a higher transmittance than the electrode α is a diaphragm side layer, the transmittance K is 7.0 in the bipolar plate side layer. By using an electrode layer of × 10 ⁻¹⁴ m ² or more and 9.1 × 10 ⁻¹⁰ m ² or less, it is expected that the energy efficiency of the entire RF battery is excellent.

  The redox flow battery of the present invention has a large capacity for the purpose of stabilizing fluctuations in power generation output, storing power when surplus generated power, load leveling, etc., for power generation of natural energy such as solar power generation and wind power generation. It can utilize suitably for this storage battery. In addition, the redox flow battery of the present invention can be suitably used as a large-capacity storage battery that is attached to a general power plant, a large commercial facility, etc., for the purpose of power supply reduction and load reduction. it can.

1 Redox flow battery (RF battery)
DESCRIPTION OF SYMBOLS 100 Battery cell 101 Diaphragm 102 Positive electrode cell 103 Negative electrode cell 104 Positive electrode 105 Negative electrode 106,107 Tank 108,109,110,111 Conduit 112,113 Pump 200 Cell stack 120 Cell frame 121 Bipolar plate
130 flow path
131 Introduction path 132 Discharge path
130a, 131a, 132a lateral groove
130b, 131b, 132b Vertical groove 122 Frame
123,124 Manifold for liquid supply
125,126 Drainage manifold α electrode α1 electrode layer
300 AC / DC Converter 310 Substation Equipment 400 Power Generation Unit 500 Load 600 Pressure Loss Measurement System 610 Measurement Cell 620 Fluid Tank 622 Fluid 630 Piping 640 Pump 650 Flow Meter 660 Differential Pressure Gauge

Claims (5)

A redox flow battery comprising a diaphragm, a bipolar plate, and an electrode disposed between the diaphragm and the bipolar plate, and charging and discharging the electrolyte through the electrode,
The bipolar plate has a flow path through which the electrolyte flows on the surface on the electrode side;
A redox flow battery, wherein the electrode includes an electrode layer having a transmittance K of 7.0 × 10 ⁻¹⁴ m ² or more and 9.1 × 10 ⁻¹⁰ m ² or less. The flow path includes an introduction path for introducing the electrolytic solution into the electrode, and a discharge path for discharging the electrolytic solution from the electrode;
The redox flow battery according to claim 1, wherein the introduction path and the discharge path are independent and independent. The introduction path and the discharge path each have a comb-shaped region,
The redox flow battery according to claim 2, wherein the introduction path and the discharge path are disposed so that the respective comb-shaped regions are opposed to each other.   The redox flow battery according to any one of claims 1 to 3, wherein the electrode layer includes a fine fiber layer mainly composed of fine fibers having a diameter of 0.005 µm to 4 µm.   The redox flow battery according to any one of claims 1 to 4, wherein a thickness of the electrode is 1000 µm or less in a state where the electrode is disposed between the diaphragm and the bipolar plate.

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