Tank and redox-flow battery system

Abstract

To provide a tank allowed to inhibit a substance, such as an electrolytic solution, within the tank from leaking outside.SOLUTION: A tank comprises a tank body and an inside layer laid on an inner surface of the tank body. The inside layer has a peel strength to the tank body smaller than a breaking strength of the inside layer.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to a tank and a redox flow battery system. [Background technology]

[0002] Patent Documents 1 and 2 disclose tanks for redox flow batteries in which an electrolyte is stored. Patent Document 1 describes lining the inner surface of a metal tank with a resin film. Patent Document 2 describes storing the tank in a container. The tank in Patent Document 2 is made of resin, rubber, or the like. The container is made of metal. The container is, for example, an international maritime cargo container that meets ISO (International Organization for Standardization) standards. It is described that a coating layer made of resin or the like is provided on the inner surface of the container. In the following description, the "metal tank" in Patent Document 1 and the "container" in Patent Document 2 may be referred to as the "tank body." The "resin film" in Patent Document 1 and the "coating layer" in Patent Document 2 may be referred to as the "inner layer." [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 10-208766 [Patent Document 2] International Publication No. 2019 / 102544 Summary of the Invention [Problem to be solved by the invention]

[0004] If a tank is subjected to an unexpected impact force due to an earthquake or other event, cracks may occur in the tank body. If a crack in the tank body progresses to the inner layer, the electrolyte inside the tank may leak out through the crack.

[0005] An object of the present disclosure is to provide a tank that can prevent substances such as electrolyte from leaking out of the tank. [Means for solving the problem]

[0006] The tank of the present disclosure comprises: The tank body and an inner layer disposed on the inner surface of the tank body; The peel strength of the inner layer relative to the tank body is smaller than the breaking strength of the inner layer. [Effects of the Invention]

[0007] The tank of the present disclosure can prevent substances such as electrolyte from leaking out of the tank. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic diagram showing the configuration of a redox flow battery system according to an embodiment. [Figure 2] FIG. 2 is a cross-sectional view showing the structure of the tank according to the embodiment. [Figure 3] FIG. 3 is an enlarged cross-sectional view showing the structure of the tank according to the embodiment. [Figure 4] FIG. 4 is a diagram illustrating a method for testing the peel strength of the inner layer of the tank according to the embodiment. [Figure 5] FIG. 5 is another view illustrating a method for testing the peel strength of the inner layer in the tank according to the embodiment. [Figure 6] FIG. 6 is a cross-sectional view showing another example of the structure of the tank according to the embodiment. [Figure 7] FIG. 7 is a diagram illustrating the method for measuring the peel strength in the test example. DETAILED DESCRIPTION OF THE INVENTION

[0009] [Description of the embodiments of the present disclosure] First, embodiments of the present disclosure will be listed and described.

[0010] (1) A tank according to an embodiment of the present disclosure includes: The tank body and an inner layer disposed on the inner surface of the tank body; The peel strength of the inner layer relative to the tank body is smaller than the breaking strength of the inner layer.

[0011] According to the tank of the present disclosure, the peel strength of the inner layer is smaller than the rupture strength of the inner layer, so that even if a crack occurs in the tank body, the occurrence of a crack in the inner layer can be suppressed. This is because the inner layer peels off from the tank body before the inner layer ruptures due to a crack that occurs in the tank body. Therefore, the tank of the present disclosure can suppress leakage of substances such as electrolyte inside the tank to the outside of the tank. The peel strength is an indicator of the adhesive strength between the tank body and the inner layer.

[0012] (2) In the tank described in (1) above, The peel strength may be 500 MPa or less.

[0013] According to the above configuration (2), the inner layer is likely to peel off from the tank body before it breaks.

[0014] (3) In the tank described in (1) or (2) above, The inner layer may be made of a resin or rubber.

[0015] According to the above configuration (3), corrosion of the tank body by the electrolyte can be suppressed.

[0016] (4) In any of the tanks (1) to (3) above, The thickness of the inner layer may be 0.5 mm or more and 20 mm or less.

[0017] According to the above configuration (4), the function of the inner layer can be fully exhibited.

[0018] (5) In any of the tanks (1) to (4) above, The tank body may be made of concrete or metal.

[0019] According to the above configuration (5), the tank body is less likely to deteriorate over a long period of time.

[0020] (6) In any of the tanks (1) to (5) above, The flatness of the inner surface of the tank body may be 5 mm or less.

[0021] According to the above configuration (6), the peel strength can be reduced, so that the inner layer is easily peeled off from the tank body before it breaks.

[0022] (7) In any of the tanks listed in (1) to (6) above The tank body has a base and a primer layer provided on the inner surface of the base, The primer layer may form the inner surface of the tank body.

[0023] According to the above configuration (7), the peel strength can be reduced, so that the inner layer is easily peeled off from the tank body before it breaks.

[0024] (8) A redox flow battery system according to an embodiment of the present disclosure includes: The battery includes a positive electrode tank for storing a positive electrode electrolyte and a negative electrode tank for storing a negative electrode electrolyte, At least one of the positive electrode tank and the negative electrode tank is any one of the tanks (1) to (7) above.

[0025] The redox flow battery system of the present disclosure includes the tank of the present disclosure, thereby making it possible to prevent leakage of the electrolyte solution in the tank.

[0026] [Details of the embodiments of the present disclosure] Hereinafter, referring to the drawings, a tank according to an embodiment of the present disclosure and a specific example of a redox flow battery system will be described. The same reference numerals in the drawings indicate the same or corresponding parts. Hereinafter, the redox flow battery system may be referred to as a "RF battery system". Note that the present invention is not limited to these examples, but is defined by the claims, and is intended to include all modifications within the meaning and scope equivalent to the claims.

[0027] <RF battery system> Referring to FIG. 1, the RF battery system 1 according to the embodiment will be described. The RF battery system 1 is an electrolytic solution circulation type secondary battery. The RF battery system 1 charges and discharges by utilizing the difference between the redox potential of the positive electrode active material contained in the positive electrode electrolytic solution and the redox potential of the negative electrode active material contained in the negative electrode electrolytic solution.

[0028] Known electrolytic solutions can be used. The positive electrode electrolytic solution contains a positive electrode active material. The positive electrode active material is, for example, one or more selected from the group consisting of manganese ions, vanadium ions, iron ions, polyacids, quinone derivatives, and amines. The negative electrode electrolytic solution contains a negative electrode active material. The negative electrode active material is, for example, one or more selected from the group consisting of titanium ions, vanadium ions, chromium ions, polyacids, quinone derivatives, and amines. A specific example of the electrolytic solution is that both the positive electrode electrolytic solution and the negative electrode electrolytic solution contain vanadium ions. Another example of the electrolytic solution is that the positive electrode electrolytic solution contains manganese ions and the negative electrode electrolytic solution contains titanium ions. The solvents of the positive electrode electrolytic solution and the negative electrode electrolytic solution are, for example, aqueous solutions containing one or more acids or acid salts selected from the group consisting of sulfuric acid, phosphoric acid, nitric acid, and hydrochloric acid.

[0029] The RF battery system 1 is typically connected to a power generation unit 8 and a load 9 via an AC / DC converter 7 and a transformer 71. The RF battery system 1 is capable of charging the power generated by the power generation unit 8 and discharging the charged power to the load 9. The power generation unit 8 is a power generation facility that uses natural energy such as solar power generation or wind power generation, or other general power plants. The RF battery system 1 is used, for example, for load leveling, momentary sag compensation, emergency power supply, and output smoothing of natural energy power generation.

[0030] The RF battery system 1 includes a battery cell 100, a positive electrode tank 2p, and a negative electrode tank 2n. The RF battery system 1 further includes a pipe 3p connecting the battery cell 100 and the positive electrode tank 2p, a pipe 3n connecting the battery cell 100 and the negative electrode tank 2n, and a pump 40 provided for each of the pipes 3p, 3n. The positive electrode tank 2p stores a positive electrode electrolyte. The negative electrode tank 2n stores a negative electrode electrolyte. The positive electrode electrolyte circulates between the positive electrode tank 2p and the battery cell 100 through the pipe 3p. The negative electrode electrolyte circulates between the negative electrode tank 2n and the battery cell 100 through the pipe 3n.

[0031] (battery cell) The battery cell 100 includes a positive electrode 104, a negative electrode 105, and a diaphragm 101. The diaphragm 101 is disposed between the positive electrode 104 and the negative electrode 105. The battery cell 100 is separated into a positive electrode cell 102 and a negative electrode cell 103 by the diaphragm 101. The positive electrode 104 is disposed in the positive electrode cell 102. The negative electrode 105 is disposed in the negative electrode cell 103. A positive electrode electrolyte is supplied to the positive electrode cell 102. A negative electrode electrolyte is supplied to the negative electrode cell 103. The battery cell 100 can be configured in any known manner as appropriate.

[0032] The pipes 3p and 3n have the same configuration. Each of the pipes 3p and 3n includes a first pipe 31 and a second pipe 32. A pump 40 is provided in the first pipe 31. The pump 40 circulates the electrolyte in the tanks 2p and 2n to the battery cell 100. The first pipe 31 in the pipe 3p is a pipe that sends the cathode electrolyte from the cathode tank 2p to the battery cell 100. The second pipe 32 in the pipe 3p is a pipe that returns the cathode electrolyte from the battery cell 100 to the cathode tank 2p. That is, the cathode electrolyte is supplied to the cathode cell 102 from the cathode tank 2p through the first pipe 31. The cathode electrolyte discharged from the cathode cell 102 is returned to the cathode tank 2p through the second pipe 32. The first pipe 31 in the pipe 3n is a pipe that sends the anode electrolyte from the anode tank 2n to the battery cell 100. The second pipe 32 in the pipe 3n is a pipe that returns the anode electrolyte from the battery cell 100 to the anode tank 2n. That is, the anode electrolyte is supplied to the anode cell 103 from the anode tank 2n through the first pipe 31. The anode electrolyte discharged from the anode cell 103 is returned to the anode tank 2n through the second pipe 32. When charging or discharging is performed, the electrolyte is circulated by the pump 40. When charging or discharging is not performed, the pump 40 is stopped and the electrolyte is not circulated.

[0033] The RF battery system 1 may be configured to include a single battery cell 100 or multiple battery cells 100. In this embodiment, as shown in FIG. 1 , the RF battery system 1 includes a cell stack 200 in which multiple battery cells 100 are stacked. The cell stack 200 is configured by repeatedly stacking a cell frame 120, a positive electrode 104, a diaphragm 101, and a negative electrode 105 in this order. End plates 210 are disposed on both ends of the cell stack 200. The cell stack 200 is integrated by clamping the end plates 210 together with clamping members 230. The cell stack 200 can be configured using any known configuration as appropriate.

[0034] The cell frame 120 has a bipolar plate 121 and a frame body 122. The bipolar plate 121 is disposed between the positive electrode 104 and the negative electrode 105. The frame body 122 is provided around the bipolar plate 121. Inside the frame body 122, a recess is formed by the bipolar plate 121 and the frame body 122. The recesses are provided on both sides of the bipolar plate 121. The positive electrode 104 and the negative electrode 105 are housed in each recess, with the bipolar plate 121 sandwiched between them.

[0035] 1, a single battery cell 100 is formed by placing a positive electrode 104 and a negative electrode 105 between the bipolar plates 121 of adjacent cell frames 120 with a diaphragm 101 sandwiched between them. An annular sealing member 127, for example, is placed between the frames 122 of each cell frame 120. The number of stacked battery cells 100 in the cell stack 200 can be selected as appropriate.

[0036] Although detailed illustration is omitted, the frame 122 has a liquid supply manifold that supplies each electrolyte solution and a liquid discharge manifold that discharges each electrolyte solution. Each manifold is provided to penetrate the frame 122, and a flow path for each electrolyte solution is formed by stacking the cell frames 120. Each of these flow paths is connected to the first pipe 31 and the second pipe 32, respectively.

[0037] <Tank> A tank 2 according to an embodiment will be described with reference to FIGS. 2 and 3. The tank 2 according to the embodiment is a positive electrode tank 2p and a negative electrode tank 2n included in the RF battery system 1 shown in FIG. 1. As shown in FIG. 2, the tank 2 includes a tank body 10 and an inner layer 20. FIG. 2 is a cross-sectional view of the tank 2 cut in the vertical direction. This vertical direction is the direction from the top surface of the tank 2 toward the bottom surface of the tank 2. In FIG. 2, the pipes 3p, 3n, etc. shown in FIG. 1 are not shown. FIG. 3 is an enlarged view of a portion of the cross section of the tank 2 shown in FIG. 2. The tank 2 stores an electrolyte 5, which is either a positive electrode electrolyte or a negative electrode electrolyte. One of the features of the tank 2 is that the peel strength of the inner layer 20 relative to the tank body 10 is smaller than the rupture strength of the inner layer 20. Because the peel strength of the inner layer 20 is smaller than the rupture strength of the inner layer 20, even if a crack occurs in the tank body 10, the occurrence of a crack in the inner layer 20 can be suppressed. Since cracks are less likely to occur in the inner layer 20, the inner layer 20 is less likely to break. Therefore, leakage of the electrolyte 5 in the tank 2 can be suppressed.

[0038] In the RF battery system 1, the more electrolyte 5 stored in the tank 2, the greater the battery capacity. In other words, the larger the volume of the tank 2, the greater the battery capacity of the RF battery system 1. The volume of the tank 2 can be appropriately selected depending on the battery capacity of the RF battery system 1. The volume of the tank 2 is, for example, 10 m 3 That's all.

[0039] (Tank body) The tank body 10 is a structural body that constitutes the tank 2. The tank body 10 serves to support the force applied to the tank 2. The tank body 10 has enough strength to maintain the shape of the tank 2 even when the electrolyte solution 5 is stored therein. The tank body 10 shown in FIG. 2 has a bottom, a top surface, and a wall. The wall connects the bottom and the top surface.

[0040] <Material> The tank body 10 is made of a durable material that is resistant to deterioration over a long period of time. The material of the tank body 10 is, for example, concrete or metal. Concrete here includes reinforced concrete. Metal is, for example, iron, iron alloy, aluminum, or aluminum alloy. Iron alloy includes steel such as carbon steel or stainless steel.

[0041] A concrete tank body 10 is easy to construct for a large-volume tank 2. Furthermore, a concrete tank body 10 can reduce costs compared to a metal tank body 10. The cost of the tank body 10 is basically determined by the amount of material used. The larger the volume of the tank 2, the more advantageous it is to construct the tank body 10 from concrete in terms of cost reduction. For example, an existing container can be used for the metal tank body 10. A specific example of an existing container is an international maritime cargo container that complies with ISO standards. Generally, these containers are made of carbon steel, such as general structural rolled steel.

[0042] (inner layer) The inner layer 20 is disposed on the inner surface 11 of the tank body 10. The inner layer 20 is bonded to the tank body 10. The inner layer 20 has an adhesive portion 21 on a surface facing the inner surface 11. The inner layer 20 is bonded to the inner surface 11 of the tank body 10 by the adhesive portion 21. The inner layer 20 has a surface facing the internal space of the tank 2. The inner layer 20 serves to suppress corrosion of the tank body 10 by the electrolyte 5. The inner layer 20 may be provided at least on a portion that comes into contact with the electrolyte 5. The inner layer 20 may be provided so as to cover the entire inner surface 11 of the tank body 10, as shown in FIG. 2. In other words, the inner layer 20 may be provided so as to cover the entire inner surface of the bottom, wall, and top of the tank body 10. In this embodiment, the inner layer 20 is in direct contact with the inner surface 11 of the tank body 10, as shown in FIG. 3.

[0043] <Material> The inner layer 20 is made of a material that is electrically insulating and resistant to the electrolyte 5. The material of the inner layer 20 is, for example, resin or rubber. The resin referred to here also includes fiber reinforced plastic (FRP), which is a composite of resin and fiber. The resin that makes up the inner layer 20 is, for example, polyethylene (PE) or polyvinyl chloride (PVC). The rubber that makes up the inner layer 20 is, for example, ethylene propylene diene rubber (EPDM) or fluororubber (FKM). The fiber contained in the FRP is, for example, at least one of glass fiber and carbon fiber.

[0044] <Thickness> The thickness of the inner layer 20 is, for example, 0.5 mm or more and 20 mm or less. The thicker the inner layer 20, the less likely defects such as pinholes will occur in the inner layer 20. The thicker the inner layer 20, the stronger the inner layer 20. If the thickness of the inner layer 20 is 0.5 mm or more, corrosion of the tank body 10 is more easily suppressed. If the thickness of the inner layer 20 is 20 mm or less, the material and cost of the inner layer 20 can be reduced. The thickness of the inner layer 20 may further be 1 mm or more and 15 mm or less, or 2 mm or more and 10 mm or less.

[0045] <Formation method> The inner layer 20 can be formed by, for example, a coating method. Examples of coating methods include a coating method and a spraying method. Specifically, the inner layer 20 is formed by applying or spraying a molten material, such as a resin, that constitutes the inner layer 20 onto the inner surface 11 of the tank body 10, and then solidifying the material. The coating or spraying process is repeated until the inner layer 20 reaches a predetermined thickness. When the inner layer 20 is formed by a coating method, the inner layer 20 is adhered to the inner surface 11 of the tank body 10 by the adhesive strength of the resin or other material contained in the inner layer 20. In this case, the inner layer 20 itself has adhesive strength, and an adhesive portion 21 is formed on the surface facing the inner surface 11. In other words, the adhesive portion 21 may be formed by the material of the inner layer 20 itself. The adhesive portion 21 is formed by the portion of the inner layer 20 that contacts the inner surface 11. The inner layer 20 made of FRP can be formed by applying a mixed material in which short fibers are mixed with resin, or by repeatedly applying resin and attaching a fiber sheet. In this embodiment, the inner layer 20 is formed by a coating method.

[0046] Alternatively, the inner layer 20 may be formed by adhering a processed sheet of a material such as resin constituting the inner layer 20 to the inner surface 11 of the tank body 10 with an adhesive. In this case, an adhesive layer (not shown) is formed on the surface of the inner layer 20 facing the inner surface 11, and the inner layer 20 is adhered to the inner surface 11 of the tank body 10 with the adhesive layer. The adhesive layer is disposed between the tank body 10 and the inner layer 20. That is, the adhesive layer is disposed on the inner surface 11 of the tank body 10, and the inner layer 20 is disposed on the adhesive layer. The material of the adhesive layer is different from the material of the inner layer 20. When the inner layer 20 is adhered to the tank body 10 with an adhesive layer, the inner layer 20 itself does not need to have adhesive strength. In a configuration in which the inner layer 20 has an adhesive layer, the inner layer 20 includes a base layer and an adhesive layer, and the adhesive layer forms the adhesive portion 21. The adhesive layer is formed with an adhesive. The adhesive is, for example, a two-component reactive epoxy adhesive or a silicone elastic adhesive.

[0047] (peel strength of inner layer against tank body) The peel strength of the inner layer 20 relative to the tank body 10 is smaller than the breaking strength of the inner layer 20. The peel strength is the strength at which the inner layer 20 peels off from the tank body 10 when the inner layer 20 is pulled in a direction along the inner surface 11 of the tank body 10. The breaking strength is the strength at which the inner layer 20 breaks when the inner layer 20 is pulled in a direction along the inner surface 11 of the tank body 10. The direction along the inner surface 11 of the tank body 10 is a direction parallel to the inner surface 11.

[0048] When the peel strength of the inner layer 20 is smaller than the breaking strength of the inner layer 20, even if a crack occurs in the tank body 10, the occurrence of a crack in the inner layer 20 can be suppressed. The reason for this is as follows: When a crack occurs in the tank body 10, the inner layer 20 is pulled in the direction in which the crack opens. In other words, a crack that occurs in the tank body 10 causes a tensile load to act on the inner layer 20 in a direction along the inner surface 11 of the tank body 10. If the peel strength of the inner layer 20 is smaller than the breaking strength of the inner layer 20, the inner layer 20 peels off from the tank body 10 before the inner layer 20 breaks due to the tensile load. As a result, a crack that occurs in the tank body 10 is less likely to propagate to the inner layer 20. In other words, even if a crack occurs in the tank body 10, a crack is less likely to occur in the inner layer 20. On the other hand, if the peel strength of the inner layer 20 is equal to or greater than the breaking strength of the inner layer 20, the inner layer 20 does not peel off from the tank body 10 due to the tensile load, and a crack occurs in the inner layer 20.

[0049] The peel strength is, for example, greater than 0 and less than 500 MPa. When the peel strength is 500 MPa, the inner layer 20 easily peels from the tank body 10. The peel strength may further be less than 300 MPa, or less than 100 MPa. The peel strength is a value greater than 0, as long as it is strong enough to support the inner layer 20 on the tank body 10. The lower limit of the peel strength is, for example, 1 MPa. When the peel strength is 1 MPa or more, it is easy to maintain the state in which the inner layer 20 is supported on the tank body 10. The peel strength may be, for example, from 1 MPa to 500 MPa, from 2 MPa to 300 MPa, from 3 MPa to 150 MPa, or from 3 MPa to 100 MPa. The peel strength was measured according to the peel strength measurement described in Test Example 1 below.

[0050] The upper limit of the peel strength may be in a range smaller than the breaking strength, and may vary depending on the material of the inner layer 20. When the material of the inner layer 20 is PE, the peel strength may be, for example, less than 35 MPa, or even 30 MPa or less. When the material of the inner layer 20 is PVC, the peel strength may be, for example, less than 60 MPa, or even 50 MPa or less. When the material of the inner layer 20 is FRP, the peel strength may be, for example, less than 500 MPa, or even 300 MPa or less. When the material of the inner layer 20 is EPDM, the peel strength may be, for example, less than 20 MPa, or even 15 MPa or less. When the material of the inner layer 20 is FKM, the peel strength may be, for example, less than 20 MPa, or even 15 MPa or less.

[0051] (Inner layer breaking strength) The breaking strength of the inner layer 20 varies depending on the material of the inner layer 20. The breaking strength of an inner layer 20 made of PE is, for example, in the range of 20 MPa to 35 MPa. The breaking strength of an inner layer 20 made of PVC is, for example, in the range of 40 MPa to 60 MPa. The breaking strength of an inner layer 20 made of FRP is, for example, in the range of 300 MPa to 500 MPa. The breaking strength of an inner layer 20 made of EPDM is, for example, in the range of 5 MPa to 20 MPa. The breaking strength of an inner layer 20 made of FKM is, for example, in the range of 7 MPa to 20 MPa. The breaking strengths were measured according to the breaking strength measurement method described in Test Example 1 below.

[0052] (Flatness of the inner surface of the tank body) The smaller the peel strength, the easier it is for the inner layer 20 to peel off from the tank body 10. For example, if the inner surface 11 of the tank body 10 is smooth, the peel strength will be smaller. The smaller the flatness of the inner surface 11 of the tank body 10, the easier it is for the inner layer 20 to peel off from the tank body 10. The flatness of the inner surface 11 can be reduced, for example, by smoothing the inner surface 11 by polishing or the like. From the perspective of reducing the peel strength, the flatness of the inner surface 11 is, for example, 5 mm or less. The flatness of the inner surface 11 may further be 4 mm or less, or 2 mm or less. The flatness referred to here is the flatness in a 100 mm square area. A 100 mm square means a square with one side measuring 100 mm. The flatness is measured in accordance with JIS B 0621:1984, "Definition and Presentation of Geometric Deviation."

[0053] Additionally, if the adhesive strength of the inner layer 20 itself is low, the peel strength will be low. Furthermore, as described above, if the inner layer 20 is adhered to the inner surface 11 of the tank body 10 by an adhesive layer, the peel strength will be low if the adhesive strength of the adhesive layer is low. If the adhesive strength of the adhesive layer is lower than the breaking strength of the inner layer 20, when the tensile load is applied, interfacial failure will occur at the interface between the inner layer 20 and the adhesive layer, or at the interface between the tank body 10 and the adhesive layer, making the inner layer 20 more likely to peel from the tank body 10. The breaking strength of the adhesive layer may be lower than the breaking strength of the inner layer 20. In this case, when the tensile load is applied, the adhesive layer itself will undergo cohesive failure, making the inner layer 20 more likely to peel from the tank body 10.

[0054] <Peel strength test method> Whether the peel strength of the inner layer 20 is smaller than the breaking strength of the inner layer 20 can be evaluated using the peel strength testing method described below. The peel strength testing method for the inner layer 20 will be described with reference to Figures 4 and 5. Similar to Figure 3, Figure 4 is an enlarged view of a portion of the cross section of the tank 2 shown in Figure 2. Figure 5 is a view of the tank 2 shown in Figure 2 from the inside. That is, Figure 5 is a view of the surface of the inner layer 20 from the front. The peel strength test is performed as follows. As shown in Figure 5, a 100 mm square area A is selected on the surface of the inner layer 20. The inner layer 20 around area A is removed to separate the inner layer 20 within area A from the inner layer 20 outside area A. As shown in Figures 4 and 5, the inner surface 11 of the tank body 10 is exposed in the area where the inner layer 20 has been removed. Area A is divided in half, and a jig 6 is fixed to one half of area A. In Figure 5, area A is divided into left and right halves, and a jig 6 is fixed to the right half. In Figure 5, the right half of region A, where jig 6 is fixed, is indicated by hatching. Jig 6 is fixed to half of region A, for example, with an adhesive. This adhesive is one that ensures that the adhesive strength between jig 6 and region A is sufficiently higher than the peel strength between the tank body 10 and the inner layer 20. Jig 6 is moved at a constant speed in a direction parallel to the inner surface 11 to pull the inner layer 20 in region A. As shown in Figure 5, if jig 6 is fixed to the right half of region A, jig 6 is moved to the right. Jig 6 may also be fixed to the left half of region A. In that case, jig 6 is moved to the left. Region A may be divided into upper and lower halves, and jig 6 may be fixed to either the upper or lower half. If jig 6 is fixed to the upper half of region A, jig 6 is moved upward. If jig 6 is fixed to the lower half of region A, jig 6 is moved downward.

[0055] When the inner layer 20 in region A is pulled by the jig 6, if the inner layer 20 in region A peels off from the tank body 10 without breaking, the peel strength of the inner layer 20 is deemed to be smaller than the breaking strength of the inner layer 20. Also, the peel strength of the inner layer 20 is deemed to be the maximum tensile load until the inner layer 20 in region A peels off divided by the area of ​​region A. When the inner layer 20 in region A breaks without peeling off from the tank body 10 when the jig 6 is pulled, the peel strength of the inner layer 20 is deemed to be equal to or greater than the breaking strength of the inner layer 20. In this case, a portion of the inner layer 20 in region A remains on the inner surface 11 of the tank body 10.

[0056] (Primer layer) As shown in FIG. 6 , the tank body 10 may have a primer layer 15. In a configuration in which the tank body 10 has the primer layer 15, the tank body 10 includes a base 10a and a primer layer 15, and the primer layer 15 forms the inner surface 11 of the tank body 10. The material of the base 10a and the material of the primer layer 15 are different. The base 10a is made of the material of the tank body 10 described above. The primer layer 15 is made of a resin, as will be described later. The primer layer 15 is provided on the inner surface of the base 10a. The primer layer 15 has a surface facing the inner layer 20. When the tank body 10 has the primer layer 15, the inner layer 20 is disposed on the surface of the primer layer 15. In other words, the primer layer 15 is located below the inner layer 20, and the primer layer 15 is disposed between the tank body 10 and the inner layer 20. The main role of the primer layer 15 is to make it easier to peel the inner layer 20 from the tank body 10, that is, to reduce the peel strength.

[0057] <Material> The primer layer 15 is made of, for example, a resin. Examples of resins constituting the primer layer 15 include epoxy (EP), acrylic (PMMA), polyester (PET), polyacetal (POM), fluororesin (PTFE), and polyurethane (PUR). EP, PMMA, and PET have excellent smoothness, allowing for the formation of a highly smooth primer layer 15. POM and PTFE have excellent lubricity, allowing for the formation of a highly lubricious primer layer 15. Having a primer layer 15 with high smoothness or lubricity makes it easier for interfacial failure to occur at the interface between the inner layer 20 and the primer layer 15 when the tensile load is applied. As a result, the peel strength is reduced, making it easier for the inner layer 20 to peel off from the tank body 10. A primer layer 15 made of PUR has low strength. When the tensile load is applied, the primer layer 15 undergoes cohesive failure, making it easier for the inner layer 20 to peel off from the tank body 10.

[0058] <Thickness> The thickness of the primer layer 15 is, for example, 0.1 mm or more and 5 mm or less. The thicker the primer layer 15, the more recesses in the inner surface of the tank body 10 can be filled by the primer layer 15. As a result, the inner surface 11 of the tank body 10 is smoothed, and the flatness of the inner surface 11 of the tank body 10 decreases. The thickness of the primer layer 15 may be small as long as the primer layer 15 can perform its function. If the thickness of the primer layer 15 is 0.1 mm or more, the inner surface 11 of the tank body 10 is easily smoothed. If the thickness of the inner layer 20 is 5 mm or less, the material and cost of the primer layer 15 can be reduced. The thickness of the primer layer 15 may further be 0.5 mm or more and 2 mm or less.

[0059] <Formation method> The primer layer 15 can be formed by, for example, a coating method. The coating method is the same as that for the inner layer 20, so a detailed description thereof will be omitted.

[0060] [Test Example 1] To evaluate the peel strength of the inner layer against the tank body, the following simulation test was conducted.

[0061] For this test, a test piece T2 shown in Figure 7 is prepared. The test piece T2 has a first member T10 simulating the tank body and a second member T20 simulating the inner layer. The area of ​​each of the first member T10 and the second member T20 is 100 mm square. The first member T10 and the second member T20 overlap within a range of 100 mm wide x 10 mm long. The remaining portion of the first member T10, which is 100 mm wide x 90 mm long, does not overlap with the second member T20.

[0062] The test piece T2 is prepared as follows. A first member T10 and an auxiliary substrate (not shown) are prepared. The auxiliary substrate has an area of ​​100 mm wide x 90 mm long. The thickness of the auxiliary substrate is the same as that of the first member T10. The 100 mm end faces of the first member T10 and the auxiliary substrate are butted together, and the first member T10 and the auxiliary substrate are arranged side by side. A masking film is applied to the surface of the first member T10, excluding a 100 mm wide x 10 mm long area from the edge that contacts the auxiliary substrate. The masking film is applied to the entire surface of the auxiliary substrate. The masking film is made of a material with excellent peelability. With the first member T10 and the auxiliary substrate aligned, the material for the second member T20 is applied in succession to the surfaces of the first member T10 and the auxiliary substrate, and then the material is solidified. This process is repeated until the second member T20 reaches the specified thickness. After the second member T20 is formed, the auxiliary substrate is removed. The second member formed in the area of ​​the first member T10 covered with the masking film is cut and removed together with the masking film. In this manner, the test piece T2 can be produced.

[0063] For this test, test pieces No. 1 to No. 7, as well as No. 101 and No. 102 were prepared. The specifications of each sample are shown in Table 1. In Table 1, "C" for the material of the first member indicates reinforced concrete, and "S" indicates carbon steel. The thickness of the reinforced concrete is 50 mm. The thickness of the carbon steel is 10 mm. The carbon steel is a rolled material. Flatness indicates the flatness of a 100 mm square area on the surface of the first member. "FRP," the material of the second member, is a mixture of PVC and short glass fibers.

[0064] For test pieces No. 1 and No. 7, the surface of the first member T10 was mechanically polished. For test pieces other than No. 1 and No. 7, the surface of the first member T10 was not mechanically polished. For test pieces No. 2 to No. 6 and No. 8, a primer layer 15 shown in Figure 6 was formed on the surface of the first member T10. The primer layer 15 was formed before the material for the second member T20 was applied. The primer layer 15 was formed by applying the material for the primer layer 15 to the surface of the first member T10 and then solidifying the material. This process was repeated until the primer layer 15 reached the specified thickness.

[0065] (Peel strength measurement) The peel strength of the second member was measured for each sample specimen. Peel strength was measured as follows: The first member T10 and the second member T20 were clamped and a tensile test was performed. The tensile test involved pulling the first member T10 and the second member T20 along the surface of the first member T10 in the direction separating them. The maximum tensile load was measured until the second member T20 peeled from the first member T10. If the second member T20 broke without peeling from the first member T10, the test was deemed unmeasurable. The maximum tensile load was divided by the overlapping area of ​​the first member T10 and the second member T20 to determine the peel strength of the second member. The peelability of the second member T20 from the first member T10 was evaluated for each sample specimen. In the tensile test, the peelability was evaluated as "A" if the second member T20 peeled from the first member T10 without breaking, and as "B" if the second member T20 broke without peeling. Table 1 shows the evaluation of the peel strength and peelability of the second member of each sample.

[0066] (Measurement of breaking strength) Furthermore, a 100mm square second member was prepared alone, and the breaking strength of the second member was measured. The breaking strength of the second member was determined by conducting a tensile test on the second member and measuring the maximum tensile stress until the second member broke. The breaking strength of the second member for each sample is shown in Table 1.

[0067] [Table 1]

[0068] All of Samples No. 1 to No. 8 received an evaluation of A for releasability. Samples No. 101 and 102 received an evaluation of B for releasability. Comparing Samples No. 1 and No. 101, and Samples No. 7 and No. 102, it appears that the flatness of the inner surface of the tank body should preferably be 5 mm or less. [Explanation of symbols]

[0069] 1 Redox flow battery system (RF battery system) 7 AC / DC converters, 71 substation equipment 8 power generation unit, 9 load 2 Tanks 2p positive electrode tank, 2n negative electrode tank 10 Tank body, 10a Base 11. Inner 15 Primer layer 20 inner layer, 21 adhesive portion 3p, 3n piping 31 First piping, 32 Second piping 40 Pump 5 Electrolyte 6 Jig 100 battery cells 101 diaphragm, 102 positive electrode cell, 103 negative electrode cell 104 positive electrode, 105 negative electrode 120 Cell Frame 121 bipolar plate, 122 frame 127 Sealing material 200 cell stack, 210 end plate, 230 fastening member Area A T2 test piece, T10 first member, T20 second member

Claims

1. The tank body and an inner layer disposed on the inner surface of the tank body; The peel strength of the inner layer relative to the tank body is smaller than the breaking strength of the inner layer. tank.

2. 2. The tank of claim 1, wherein the peel strength is 500 MPa or less.

3. The tank according to claim 1 , wherein the material of the inner layer is resin or rubber.

4. 2. The tank according to claim 1, wherein the thickness of the inner layer is 0.5 mm or more and 20 mm or less.

5. The tank according to claim 1, wherein the material of the tank body is concrete or metal.

6. 2. The tank according to claim 1, wherein the flatness of the inner surface of the tank body is 5 mm or less.

7. The tank body has a base and a primer layer provided on the inner surface of the base, The tank of claim 1 , wherein the primer layer forms an inner surface of the tank body.

8. The battery includes a positive electrode tank for storing a positive electrode electrolyte and a negative electrode tank for storing a negative electrode electrolyte, At least one of the positive electrode tank and the negative electrode tank is the tank according to any one of claims 1 to 7. Redox flow battery system.

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