Redox flow battery

Abstract

To provide a redox flow battery with high efficiency and high output.SOLUTION: A redox flow battery 1 includes a cell unit 20 which includes a frame body 21 with an opening 22 and an electrode assembly 30 that comprises a plurality of laminated sheets 31 accommodated in the opening 22, and has a positive electrode cell 11 and a negative electrode cell 12 formed between a barrier membrane 13 on one side and the electrode assembly and between the barrier membrane 13 on the other side and the electrode assembly, respectively. Each of the laminated sheets 31 includes first and second layers 32, 33 laminated with each other. The first layer 32 includes a sheet-like positive electrode 14 protruding outward from one end surface 33a of the second layer 33 to be located within the positive electrode cell 11, and a sheet-like negative electrode 15 protruding outward from the other end surface 33a of the second layer 33 to be located within the negative electrode cell 12, and one of the first and second layers 32, 33 contains a conductive material electrically connecting the positive electrode 14 and the negative electrode 15.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a redox flow battery. [Background technology]

[0002] Redox flow batteries, which charge and discharge using the oxidation-reduction reaction of active materials contained in an electrolyte, have been known as secondary batteries for power storage. Redox flow batteries have advantages such as easy capacity increase, long life, and the ability to accurately monitor the battery's state of charge. Due to these advantages, redox flow batteries have attracted considerable attention in recent years for applications such as stabilizing the output of renewable energy sources, which have large fluctuations in power generation, and leveling power loads.

[0003] Generally, redox flow batteries are composed of a cell stack in which multiple battery cells are stacked to obtain a predetermined voltage. To achieve high efficiency throughout the system, such redox flow batteries are required to reduce the internal resistance of the battery cells and the pressure loss caused by the electrolyte passing through the battery cells. To meet these requirements, Patent Document 1 describes a redox flow battery with comb-like channels in the bipolar plates that make up the battery cells. The comb-like channels are formed on the surfaces of the bipolar plates facing the electrodes, and consist of two types of channel grooves, the supply side and the discharge side, arranged in an interdigitated manner. With this configuration, the electrolyte flows through the electrode from the supply side channel groove to the adjacent discharge side channel groove. This is expected to reduce the thickness of the electrode, thereby reducing the internal resistance, and also reduce the flow resistance of the electrolyte within the electrode, thereby reducing the pressure loss. Patent Document 1 also describes a technology to address the problems inherent in a structure with comb-like channels, in which the electrode has a two-layer structure in which the permeability of the layer on the diaphragm side is greater than that of the layer on the bipolar plate side. This is expected to reduce uneven flow of the electrolyte within the electrode, and solve the problem of the electrolyte flow becoming uneven within the electrode and preventing the entire electrode from being effectively utilized in the reaction.

[0004] Meanwhile, as another structure that satisfies the above requirements, Patent Document 2 describes a structure that includes a flow path structure that circulates the electrolyte so that the electrolyte flows in the thickness direction within the electrode. This flow path structure is expected to reduce the internal resistance and pressure loss by making the electrode thinner, and is also expected to reduce uneven flow of the electrolyte within the electrode. [Prior art documents] [Non-patent literature]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-122230 [Patent Document 2] Special Publication No. 2015-530709 Summary of the Invention [Problem to be solved by the invention]

[0006] In the redox flow batteries described in Patent Documents 1 and 2, it is necessary to devise a flow path structure within the battery cell to ensure that the electrolyte flows as uniformly as possible within the electrodes. Therefore, the flow path structure within the battery cell is inevitably complex. Therefore, if an attempt is made to increase the size of the battery cell in response to demands for higher output from redox flow batteries, the flow resistance of the electrolyte throughout the battery cell increases, resulting in increased pressure loss.

[0007] Therefore, an object of the present invention is to provide a redox flow battery that is highly efficient and has high output. [Means for solving the problem]

[0008] In order to achieve the above-mentioned object, the redox flow battery of the present invention has cell units and diaphragms stacked alternately in a first direction, the cell units comprising: a frame having an opening penetrating in the first direction; and an electrode assembly housed in the opening and made of a plurality of laminated sheets stacked in a second direction perpendicular to the first direction, the electrode assembly forming a positive electrode cell between the frame and the diaphragm on one side in the first direction, and a negative electrode cell between the frame and the diaphragm on the other side in the first direction, the electrode assembly being configured such that a positive electrode fluid containing a positive electrode active material is introduced into the positive electrode cell through the opening penetrating in the second direction perpendicular to the first direction. and a negative electrode side flow path that allows a negative electrode fluid containing a negative electrode active material to flow in the second direction within the negative electrode cell, and each of the plurality of laminated sheets has first and second layers stacked on top of each other, the first layer including a sheet-like positive electrode electrode that protrudes outward from an end face on one side of the second layer and is located within the positive electrode cell, and a sheet-like negative electrode electrode that protrudes outward from an end face on the other side of the second layer and is located within the negative electrode cell, and either the first or second layer has a conductive material that electrically connects the positive electrode and the negative electrode.

[0009] This type of redox flow battery allows the electrolyte (a fluid containing active material) to pass through the sheet-like electrodes in the thickness direction without requiring a special and complex flow path structure. Therefore, even if the battery cell size is increased, the flow resistance of the electrolyte does not increase significantly, and the pressure loss when the electrolyte passes through the battery cell does not increase significantly. Furthermore, because the cell unit has a simple structure, the assembly accuracy of the cell stack can be improved. This not only suppresses electrolyte bias, but also maximizes charge / discharge performance. [Effects of the Invention]

[0010] As described above, according to the present invention, a highly efficient and high-power redox flow battery can be provided. [Brief explanation of the drawings]

[0011] [Figure 1]FIG. 1 is a schematic configuration diagram of a redox flow battery according to a first embodiment of the present invention. [Figure 2] 1 is a schematic plan view of a cell frame according to a first embodiment of the present invention. [Figure 3] 1 is a schematic view of an electrode assembly according to a first embodiment of the present invention. [Figure 4] 1 is a schematic diagram showing the internal structure of a battery cell according to a first embodiment of the present invention. [Figure 5] FIG. 4 is a schematic view of an electrode assembly according to a second embodiment of the present invention. [Figure 6] FIG. 10 is a schematic view of an electrode assembly according to a third embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0013] (First embodiment) Fig. 1(a) is a schematic diagram of a redox flow battery according to a first embodiment of the present invention. Fig. 1(b) is a schematic diagram of a cell stack constituting the redox flow battery of this embodiment. Note that Fig. 1(b) merely shows the relative relationships between components, and does not accurately represent the arrangement or shape of each component.

[0014] The redox flow battery 1 is charged and discharged using an oxidation-reduction reaction of the positive electrode active material and the negative electrode active material in the battery cells 10, and includes a cell stack 2 having a plurality of stacked battery cells 10. The plurality of battery cells 10 are configured by alternately stacking cell units 20 and diaphragms 13, which will be described later. The detailed configuration of the cell unit 20 will be described later. Although four battery cells 10 are shown in FIG. 1(b), the number of battery cells 10 that make up the cell stack 2 is not limited to this.

[0015] The cell stack 2 is connected to a positive electrode tank 3, which stores a positive electrode electrolyte, via a positive electrode outflow pipe L1 and a positive electrode return pipe L2. A positive electrode pump 4 is provided in the positive electrode outflow pipe L1, which circulates the positive electrode electrolyte between the positive electrode tank 3 and the cell stack 2. The cell stack 2 is also connected to a negative electrode tank 5, which stores a negative electrode electrolyte, via a negative electrode outflow pipe L3 and a negative electrode return pipe L4. A negative electrode pump 6 is provided in the negative electrode outflow pipe L3, which circulates the negative electrode electrolyte between the negative electrode tank 5 and the cell stack 2. Note that the electrolyte may be any fluid containing an active material, such as a slurry formed by suspending and dispersing granular active material in a liquid phase, or the active material itself in a liquid state. Therefore, the electrolyte referred to here is not limited to a solution of active material.

[0016] Each battery cell 10 has a positive electrode cell 11, a negative electrode cell 12, and a diaphragm 13 separating the positive electrode cell 11 and the negative electrode cell 12. The positive electrode cell 11 includes a positive electrode 14, and is configured so that a positive electrode electrolyte (positive electrode fluid) flows through the positive electrode cell 11 in a direction perpendicular to the stacking direction of the cell stack 2. The negative electrode cell 12 includes a negative electrode 15, and is configured so that a negative electrode electrolyte (negative electrode fluid) flows through the negative electrode cell 12 in a direction perpendicular to the stacking direction of the cell stack 2. Hereinafter, the stacking direction (first direction) of the cell stack 2 is referred to as the Z direction, and the flow direction of the electrolyte within the battery cell 10 (second direction) is referred to as the X direction.

[0017] The positive electrode cell 11 is connected to the positive electrode outflow piping L1 via an individual supply flow path P1 and a common supply flow path C1, and to the positive electrode return piping L2 via an individual recovery flow path P2 and a common recovery flow path C2. This allows the positive electrode cell 11 to be supplied with a positive electrode electrolyte solution containing a positive electrode active material from the positive electrode tank 3. This allows the positive electrode cell 11 to undergo an oxidation reaction during charging, whereby the reduced positive electrode active material is converted to an oxidized state, and a reduction reaction during discharging, whereby the oxidized positive electrode active material is converted to a reduced state. Meanwhile, the negative electrode cell 12 is connected to the negative electrode outflow piping L3 via an individual supply flow path P3 and a common supply flow path C3, and to the negative electrode return piping L4 via an individual recovery flow path P4 and a common recovery flow path C4. This allows the negative electrode cell 12 to be supplied with a negative electrode electrolyte solution containing a negative electrode active material from the negative electrode tank 5. Thus, in the negative electrode cell 12, a reduction reaction occurs during charging, in which the oxidized negative electrode active material changes to a reduced state, and an oxidation reaction occurs during discharging, in which the reduced negative electrode active material changes to an oxidized state.

[0018] Fig. 2 is a schematic plan view of a cell unit constituting a battery cell of this embodiment, showing a plane viewed from the stacking direction of the cell stack. Note that the arrangement of each component shown in Fig. 2 and the following drawings is for convenience and does not limit the position of the battery cell when in use. Furthermore, the terms "upper" and "lower" in the following description are relative terms and do not limit the position of the battery cell when in use.

[0019] The cell units 20 are stacked together with the diaphragms 13 in the Z direction to form multiple battery cells 10, and include a frame 21 and an electrode assembly 30 including a positive electrode 14 and a negative electrode 15. The frame 21 has a rectangular opening 22 that penetrates in the Z direction, and the electrode assembly 20 is liquid-tightly housed in the opening 22. The opening 22 in the frame 21 is closed by the diaphragms 13 that are stacked on both sides of the cell unit 20, thereby forming a positive electrode cell 11 or a negative electrode cell 12 between the electrode assembly 30 and the diaphragms 13. That is, a positive electrode cell 11 is formed between the electrode assembly 30 and the diaphragm 13 on one side (the front side of the paper in FIG. 2), and a negative electrode cell 12 is formed between the electrode assembly 30 and the diaphragm 13 on the other side (the back side of the paper in FIG. 2).

[0020] Even if the diaphragm 13, which is an ion exchange membrane, is provided over the entire surface of the frame 21, the portion excluding the opening 22, i.e., the portion not facing the electrode assembly 30, does not function as a battery cell 10. As a result, the expensive ion exchange membrane is wasted. Therefore, the diaphragm 13 may be provided only in the portion of the frame 21 facing the electrode assembly 30, and for this purpose, the frame 21 may further have, for example, a cover member with an opening that exposes only the electrode assembly 30. In other words, the cell units 20 and the diaphragms 13 may be stacked alternately with such a cover member interposed therebetween.

[0021] Frame 21 has through holes 23a to 26a formed near four corners, each penetrating frame 21 in the Z direction. In addition, frame 21 has flow channel grooves 23b and 24b on one surface (the surface on the front side of the paper in FIG. 2) that connect through holes 23a and 24a with opening 22, and has flow channel grooves 25b and 26b on the other surface (the surface on the back side of the paper in FIG. 2) that connect through holes 25a and 26a with opening 22. Although not shown in detail, flow channel grooves 25b and 26b on the other side have the same structure as flow channel grooves 23b and 24b on one side, respectively.

[0022] When cell units 20 and diaphragms 13 are alternately stacked to form cell stack 2, through holes 23a, 24a and flow path grooves 23b, 24b form positive electrode-side flow paths C1, C2, P1, P2 that circulate positive electrode electrolyte in the X direction within positive electrode cell 11. Specifically, through hole 23a and flow path groove 23b form common supply flow path C1 and individual supply flow path P1 for positive electrode electrolyte, respectively, and through hole 24a and flow path groove 24b form common recovery flow path C2 and individual recovery flow path P2 for positive electrode electrolyte, respectively. In this way, the positive electrode electrolyte is supplied from the common supply flow path C1 through the individual supply flow path P1 to positive electrode cell 11, flows through positive electrode cell 11 in the X direction, and is then recovered from the individual recovery flow path P2 to the common recovery flow path C2.

[0023] Meanwhile, the through holes 25a, 26a and the flow path grooves 25b, 26b constitute anode-side flow paths C3, C4, P3, and P4 that circulate the anode electrolyte in the X direction within the anode cell 12 when the cell units 20 and the diaphragms 13 are alternately stacked to form the cell stack 2. Specifically, the through holes 25a and the flow path grooves 25b constitute the common supply flow path C3 and the individual supply flow path P3 for the anode electrolyte, respectively, and the through holes 26a and the flow path grooves 26b constitute the common supply flow path C4 and the individual supply flow path P4 for the anode electrolyte, respectively. In this way, the anode electrolyte is supplied from the common supply flow path C3 through the individual supply flow path P3 to the anode cell 12, flows through the anode cell 12 in the X direction, and is then recovered from the individual recovery flow path P4 to the common recovery flow path C4.

[0024] At this time, it is preferable that the electrolytic solution does not stagnate in the flow paths P1 to P4, and is supplied to and recovered from each of the cells 11 and 12 without being biased in the Y direction. For this reason, as shown in the figure, it is preferable that each of the flow path grooves 23b and 24b gradually widens from the middle toward the opening 22, and then branches into multiple paths to connect to the opening 22. Furthermore, although not shown in detail, it is also preferable that each of the flow path grooves 25b and 26b gradually widens from the middle toward the opening 22, and then branches into multiple paths to connect to the opening 22.

[0025] The frame 21 may be made up of multiple members, for example, four frame members on the top, bottom, left, and right, and may additionally include the cover member described above. The frame 21 may be made of an insulating material, particularly one that has appropriate rigidity, does not react with the electrolyte, and is resistant to the electrolyte (chemical resistance, acid resistance, etc.). Examples of such materials include plastics such as vinyl chloride, polyethylene, and polypropylene.

[0026] Fig. 3(a) is a schematic cross-sectional view of the electrode assembly of this embodiment, showing a cross section parallel to the stacking direction of the cell stack. Fig. 3(b) is an exploded plan view of a laminated sheet constituting the electrode assembly of this embodiment. Fig. 4 is a schematic diagram showing the internal structure of a battery cell of this embodiment, showing the structure as seen from a direction perpendicular to the stacking direction of the cell stack and the flow direction of the electrolyte within the battery cell.

[0027] The electrode assembly 30 is made up of a plurality of laminated sheets 31 laminated in the X direction, and each laminated sheet 31 has an electrode layer (first layer) 32 and a spacer layer (second layer) 33 laminated on the electrode layer 32. Note that the number of laminated sheets 31 constituting the electrode assembly 30 is not limited to the number shown in the figure.

[0028] The electrode layer 32 includes a sheet-like positive electrode 14 and a sheet-like negative electrode 15. The positive electrode 14 and the negative electrode 15 are spaced apart in the Z direction and extend in the Y direction. The positive electrode 14 protrudes outward from one end face (end face on one side) 33a of the spacer layer 33 in the Z direction, and the negative electrode 15 protrudes outward from the other end face (end face on the other side) 33b of the spacer layer 33 in the Z direction. As a result, when the cell units 20 and the diaphragms 13 are alternately stacked to form the cell stack 2, as shown in FIG. 4, the positive electrode 14 is disposed in the positive cell 11 perpendicular to the X direction (the flow direction of the positive electrolyte), and the negative electrode 15 is disposed in the negative cell 12 perpendicular to the X direction (the flow direction of the negative electrolyte). The electrodes 14 and 15 are preferably made of a carbon material. For example, the electrodes 14 and 15 may be made of carbon paper, carbon cloth, or carbon felt. The thickness of each of the electrodes 14 and 15 is not particularly limited, and is, for example, about 0.3 mm.

[0029] The electrode layer 32 also includes an intermediate region 34 disposed between the positive electrode 14 and the negative electrode 15. The intermediate region 34 functions to seal the gap between the electrode layer 32 and the spacer layer 33 and prevent leakage of the electrolyte solution from the gap between them. Therefore, the material of the intermediate region 34 is preferably resistant to the electrolyte solution and able to withstand a certain level of liquid pressure (the pressure difference between the positive and negative electrodes). Examples of such materials include soft vinyl chloride, thermoplastic elastomer, rubber, and resin materials such as polytetrafluoroethylene (PTFE). Note that the intermediate region 34 does not necessarily need to be in contact with the electrodes 14 and 15 as long as it can fully perform the above-mentioned sealing function.

[0030] The spacer layer 33 is interposed between the electrode layers 32 in the electrode assembly 30, and thus serves to form gaps between the positive electrodes 14 and the negative electrodes 15 of two adjacent electrode layers 32. The spacer layer 33 is made of a conductive material and serves to electrically connect the positive electrodes 14 and the negative electrodes 15 in the electrode layers 32, i.e., to electrically connect two adjacent battery cells 10 in the cell stack 2. A carbon material with high conductivity and resistance to the electrolyte is preferably used as the conductive material for the spacer layer 33. Additionally, the conductive material for the spacer layer 33 is preferably selected from the perspectives of mass production and cost. Examples of such materials include expanded graphite, which can be manufactured into a roll and has excellent workability. The thickness of the spacer layer 33 is not particularly limited and is, for example, approximately 0.2 mm.

[0031] With this configuration, the sheet-like electrodes 14, 15 can be arranged perpendicular to the flow direction (X direction) of the electrolyte within the cells 11, 12 by protruding outward beyond both end surfaces 33a, 33b of the spacer layer 33 that defines the internal space of the cells 11, 12. In this case, the pressure loss when the electrolyte passes through the electrodes 14, 15 is much greater than the pressure loss when the electrolyte passes through other regions (voids created by the spacer layer 33) within the cells 11, 12. Therefore, the electrolyte can pass in the thickness direction of the electrodes 14, 15 without complicating the flow path structure within the cells 11, 12 and while suppressing the occurrence of uneven flow within the electrodes 14, 15. As a result, even if the size of the battery cell 10 is increased, the flow resistance of the electrolyte does not increase significantly, and the pressure loss when the electrolyte passes through the battery cell 10 does not increase significantly.

[0032] Furthermore, because the cell unit 20 can be handled as a single component during assembly of the cell stack 2, the number of components can be reduced and the manufacturing process can be simplified, enabling mass production of the redox flow battery 1 at low cost. Additionally, because the cell unit 20 has a simple structure, it is easy to arrange many electrodes 14, 15 within the battery cell 10, and the cell stack 2 can be assembled with high precision. This makes it possible to arrange the positive electrode 14 and the negative electrode 15, sandwiching the diaphragm 13, in the designed positions, reliably form gaps between the electrodes, and ensure appropriate flow paths within the battery cell 10, thereby preventing problems such as interference between components. This maximizes the charge / discharge performance of the battery cell 10, enabling a highly efficient and high-power redox flow battery 1 to be realized.

[0033] The protruding length of each electrode 14, 15 from each end surface 33a, 33b of the spacer layer 33 is not particularly limited, as long as it is appropriately set taking into consideration the expected pressure loss of the electrolyte and the mechanical strength of the protruding portion, and is, for example, approximately 0.5 to 3 mm. Note that, to mechanically support the protruding portion of each electrode 14, 15, a porous or fibrous spacer made of a resin material may be inserted into the gap portion of each cell 11, 12, as long as it does not significantly interfere with the movement of hydrogen ions during charge and discharge. Furthermore, sheet-like electrodes may be inserted into the gap portion of each cell 11, 12, as long as the pressure loss of the electrolyte is within an acceptable range.

[0034] The method for manufacturing the laminate sheet 31 is not particularly limited. For example, the laminate sheet 31 can be manufactured by bonding separately manufactured electrode layers 32 and spacer layers 33 together by thermocompression bonding. Alternatively, the laminate sheet 31 may be manufactured by forming the electrode layer 32 on a previously prepared spacer layer 33. For example, the electrodes 14 and 15 are disposed at predetermined positions on the spacer layer 33, and then a liquid resin material is applied between the electrodes 14 and 15 and cured. In this case, the electrical connection between the spacer layer 33 and the electrodes 14 and 15 is ensured by the pressure generated when another laminate sheet 31 (spacer layer 33) is laminated on the laminate sheet 31. Furthermore, the laminate sheet 31 is not limited to a configuration having one electrode layer 32 and one spacer layer 33, but may be composed of an electrode layer 32 and a pair of spacer layers 33 laminated on both sides of the electrode layer 32. In such a configuration, for example, the area that will become the intermediate region 34 of the electrode layer 32 may be formed in advance on each of a pair of spacer layers 33, and the electrodes 14, 15 may be sandwiched between such a pair of spacer layers 33 to manufacture the laminated sheet 31.

[0035] From the viewpoint of simplifying the manufacturing process, each of the electrodes 14, 15 constituting the electrode layer 32 may itself have a multilayer structure. This increases the thickness of the electrode layer 32, allowing the electrode assembly 30 of the same thickness to be assembled in fewer steps. However, since the thickness of each of the electrodes 14, 15 also increases, there is a concern that the conductivity in the thickness direction may decrease. Therefore, when each of the electrodes 14, 15 has a multilayer structure, the thickness of the electrode layer 32 is preferably large enough to prevent a significant decrease in the conductivity in the thickness direction, for example, about 5 mm.

[0036] In the illustrated embodiment, the multiple battery cells 10 are connected to each other so that the electrolytes flow in parallel through the multiple battery cells 10, but the connection configuration of the multiple battery cells 10 is not limited to this. For example, the multiple battery cells 10 may be connected to each other so that the electrolytes flow in series through the multiple battery cells 10, i.e., they may form a series flow path. Alternatively, the multiple battery cells 10 may have a hierarchical flow path configuration that combines parallel flow paths and series flow paths, specifically, a flow path configuration in which multiple series flow paths are connected in parallel. That is, the cell stack 2 may be divided into multiple cell groups, and the multiple battery cells 10 that make up each cell group may form a series flow path, and each cell group may form a parallel flow path.

[0037] In addition, in a flow path configuration in which multiple serial flow paths are connected in parallel, the positive electrode tank 3 may be divided into two tanks, one connected to the pipe L1 and the other connected to the pipe L2, and two types of positive electrode electrolytes having different ratios of the active material concentration in a reduced state to the active material concentration in an oxidized state may be stored separately in these two tanks. That is, the positive electrode electrolyte may be stored in separate tanks before and after the redox reaction during charge / discharge operations. Similarly, the negative electrode tank 5 may be divided into two tanks, one connected to the pipe L3 and the other connected to the pipe L4, and two types of negative electrode electrolytes having different ratios of the active material concentration in a reduced state to the active material concentration in an oxidized state may be stored separately in these two tanks. That is, the negative electrode electrolyte may be stored in separate tanks before and after the redox reaction during charge / discharge operations.

[0038] (Second embodiment) FIG. 5(a) is a schematic cross-sectional view of an electrode assembly according to a second embodiment of the present invention, showing a cross section parallel to the stacking direction of the cell stack. FIG. 5(b) is an exploded plan view of a laminated sheet constituting the electrode assembly of this embodiment. This embodiment is a modification of the first embodiment, in which the configuration of the electrode assembly has been changed. Below, only the configuration of the electrode assembly of this embodiment that differs from the first embodiment will be described.

[0039] In this embodiment, the laminate sheet 31 includes a third layer, a reinforcing layer 35, in addition to the electrode layer 32 and the spacer layer 33. The reinforcing layer 35 is laminated on the side of the spacer layer 33 opposite the electrode layer 32 and serves to reinforce the spacer layer 33, preferably made of expanded graphite. Therefore, the material for the reinforcing layer 35 is preferably resistant to the electrolyte and has adequate mechanical strength. Examples of such materials include resin materials such as soft polyvinyl chloride and thermoplastic elastomer. For example, the reinforcing layer 35 can be laminated on the spacer layer 33 by attaching a resin sheet to the spacer layer 33 by thermocompression bonding, or by applying a liquid resin material to the spacer layer 33 and then curing it.

[0040] The reinforcing layer 35 also has a main region 36 having the same shape as the spacer layer 33, and multiple protrusions 37a, 37b formed on both end faces 36a, 36b of the main region 36 in the Z direction, spaced apart in the Y direction. The multiple protrusions 37a formed on one end face 36a of the main region 36 function to support the portion of the positive electrode 14 that protrudes from one end face 33a of the spacer layer 33. Meanwhile, the multiple protrusions 37b formed on the other end face 36b of the main region 36 function to support the portion of the negative electrode 15 that protrudes from the other end face 33b of the spacer layer 33. Thus, the reinforcing layer 35 not only reinforces the spacer layer 33, but also mechanically supports the protruding portions of the electrodes 14, 15. Note that if the mechanical strength of the protruding portions of the electrodes 14, 15 is sufficiently ensured, the multiple protrusions 37a, 37b may be omitted.

[0041] (Third embodiment) FIG. 6(a) is a schematic cross-sectional view of an electrode assembly according to a third embodiment of the present invention, showing a cross section parallel to the stacking direction of the cell stack. FIG. 6(b) is an exploded plan view of a laminated sheet constituting the electrode assembly of this embodiment. This embodiment is a modification of the first embodiment, in which the combination of materials constituting the electrode assembly is changed. Below, only the configuration of the electrode assembly of this embodiment that differs from the first embodiment will be described.

[0042] In this embodiment, the material constituting the intermediate region 34 of the electrode layer 32 and the material constituting the spacer layer 33 are different from those in the first embodiment. Specifically, the intermediate region 34 of the electrode layer 32 is made of the same conductive material as the spacer layer 33 in the first embodiment, and the spacer layer 33 is made of the same resin material as the intermediate region 34 of the electrode layer 32 in the first embodiment. Therefore, the intermediate region 34 of the electrode layer 32 has the same function as the spacer layer 33 in the first embodiment, i.e., the function of electrically connecting the positive electrode 14 and the negative electrode 15 in the electrode layer 32. Furthermore, in addition to the function of forming gaps between the positive electrodes 14 and the negative electrodes 15 as in the first embodiment, the spacer layer 33 also has the same function as the intermediate region 34 of the electrode layer 32 in the first embodiment, i.e., the function of sealing between the electrode layer 32 and the spacer layer 33.

[0043] The electrode layer 32 and the spacer layer 33 can be laminated, for example, by attaching a resin sheet to the electrode layer 32 by thermocompression bonding or by applying a liquid resin material to the electrode layer 32 and then curing it. When the intermediate region 34 is made of expanded graphite, the electrode layer 32 can be manufactured by rolling the expanded graphite into a sheet and simultaneously integrating the electrodes 14, 15 with the expanded graphite by pressing.

[0044] In this embodiment, multiple protrusions 37a, 37b similar to those formed on the reinforcing layer 35 of the second embodiment are formed on both end surfaces 33a, 33b of the spacer layer 33. That is, multiple protrusions 37a supporting the portion of the positive electrode 14 protruding from the end surface 33a of the spacer layer 33 are formed on one end surface 33a of the spacer layer 33. Multiple protrusions 37b supporting the portion of the negative electrode 15 protruding from the other end surface 33b of the spacer layer 33 are formed on the other end surface 33b of the spacer layer 33. As in the second embodiment, the multiple protrusions 37a, 37b may be omitted if the mechanical strength of the protruding portions of the electrodes 14, 15 is sufficiently ensured. [Explanation of symbols]

[0045] 1. Redox flow battery 10 battery cells 11 Positive electrode cell 12 negative electrode cells 13 Diaphragm 14 Positive electrode 15 Negative electrode 20 cell units 21 Frame 22 Opening 23a~26a Through hole 23b~26b Flow channel groove 30 Electrode assembly 31 Laminated Sheet 32 Electrode layer 33 Spacer layer 33a,33b end face 34 Intermediate area 35 Reinforcement layer 36 Main area 36a,36b end face 37a,37b protrusion

Claims

1. The cell unit and the diaphragm are stacked alternately in a first direction, The cell unit is a frame having an opening penetrating in the first direction; an electrode assembly accommodated in the opening and made of a plurality of laminated sheets stacked in a second direction perpendicular to the first direction, the electrode assembly forming a positive electrode cell between itself and the diaphragm on one side in the first direction, and forming a negative electrode cell between itself and the diaphragm on the other side in the first direction, the frame has a positive electrode side flow path that allows a positive electrode fluid containing a positive electrode active material to flow in the positive electrode cell in a second direction perpendicular to the first direction, and a negative electrode side flow path that allows a negative electrode fluid containing a negative electrode active material to flow in the second direction in the negative electrode cell, a redox flow battery having: each of the plurality of laminated sheets being first and second layers stacked on each other, the first layer including a sheet-like positive electrode protruding outward from the end face on the one side of the second layer and positioned within the positive electrode cell, and a sheet-like negative electrode protruding outward from the end face on the other side of the second layer and positioned within the negative electrode cell, and either the first or second layer including a conductive material that electrically connects the positive electrode and the negative electrode.

2. 2. The redox flow battery according to claim 1, wherein the positive electrode and the negative electrode are spaced apart from each other in the first direction and extend in a third direction perpendicular to the first direction and the second direction.

3. 3. The redox flow battery of claim 2, wherein the second layer consists of the conductive material.

4. 4. The redox flow battery according to claim 3, wherein each of the plurality of laminated sheets further includes a third layer made of a resin material and laminated on the second layer on the side opposite to the first layer.

5. 5. The redox flow battery according to claim 4, wherein the third layer has a region having the same shape as the second layer, and a plurality of protrusions formed on an end surface of the region in the first direction at intervals in the third direction and supporting a portion of the positive electrode or the negative electrode protruding from the end surface of the second layer.

6. 3. The redox flow battery according to claim 2, wherein the first layer is provided between the positive electrode and the negative electrode and includes a region made of a resin material for sealing between the first layer and the second layer.

7. 3. The redox flow battery according to claim 2, wherein the first layer includes a region made of the conductive material and provided between the positive electrode and the negative electrode, and the second layer is made of a resin material and has a function of reinforcing the first layer.

8. 8. The redox flow battery according to claim 7, wherein the second layer has a plurality of protrusions formed on the end surface at intervals in the third direction and supporting a portion of the positive electrode or the negative electrode protruding from the end surface of the second layer.

9. 9. The redox flow battery according to claim 1, wherein the conductive material is expanded graphite.

10. 9. The redox flow battery according to claim 1, wherein the cell unit has a porous or fibrous spacer inserted in the positive electrode cell or the negative electrode cell.

11. 9. The redox flow battery according to claim 1, wherein the positive electrode and the negative electrode are made of carbon paper, carbon cloth, or carbon felt.

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