KR20140046774A - Bipolar plate for redox flow battery and redox flow battery comprising said bipolar plate - Google Patents

Abstract

The present invention relates to a bipolar plate for a redox flow battery and a redox flow battery containing the same, more particularly, to a bipolar plate for a redox flow battery used in a redox flow battery comprising: a plurality of serially stacked battery cells and supplying a negative electrode electrolyte and a positive electrode electrolyte to the stacked battery cells in turn, wherein the battery cells are composed of a pair of electrode plates separated into a positive electrode plate and a negative electrode plate; a membrane interposed between the electrode plates; a bipolar plate spaced apart from the external side of the electrode. The bipolar plate comprises a double structure composed of a core unit made of metal or carbon fiber, and a graphite surface layer formed on the external side of the core unit. According to the present invention, provided is the bipolar plate for a redox flow battery with a dual structure of a core unit made of metal and the likes and a carbon surface layer on the external side of the core unit, so that the electrical characteristics are similar to those of the conventional bipolar plate; the shape thereof is easily processed; mechanical rigidity can be secured; the durability of the electrolyte is maintained; and manufacturing costs can be lowered.

Description

Redox flow battery separator and redox flow battery including the separator {BIPOLAR PLATE FOR REDOX FLOW BATTERY AND REDOX FLOW BATTERY COMPRISING SAID BIPOLAR PLATE}

The present invention relates to a redox flow battery separator and a redox flow battery including the separator, and more particularly, a pair of electrode plates divided into a positive electrode plate and a negative electrode plate, and a membrane interposed between the electrode plates. And a plurality of battery cells composed of a plurality of separator cells arranged in series separated from the outside of the electrode, and stacked battery cells in a separator plate for a redox flow battery used in a redox flow battery that cross-feeds a cathode electrolyte solution and an anode electrolyte solution. The separator includes a double structure of a core part made of metal or carbon fiber and a graphite surface layer formed on the outside of the core part, and a redox flow cell including the separator. It is about.

Recently, renewable energy, such as solar energy and wind energy, has been spotlighted as a method for suppressing greenhouse gas emission, which is a major cause of global warming, and a lot of researches are being carried out for their practical use. However, renewable energy is greatly affected by the site environment and natural conditions. Moreover, there is a disadvantage in that renewable energy cannot supply energy evenly continuously because the output fluctuates severely. Therefore, in order to use renewable energy for home or commercial use, a system that stores energy when the output is high and uses the stored energy when the output is low is used.

As such an energy storage system, a large-capacity secondary battery is used. For example, a large-capacity secondary battery storage system is introduced into a large-scale solar power generation and wind power generation complex. The secondary battery for storing a large amount of power includes a lead acid battery, a NaS battery, and a redox flow battery (RFB). Although the lead acid battery is widely used in comparison with other batteries, it has disadvantages such as low efficiency and maintenance cost due to periodical replacement and disposal of industrial waste generated when the battery is replaced. The NaS battery has a disadvantage in that it operates at a high temperature of 300 ° C or higher, although it has an advantage of high energy efficiency. The redox flow battery has been researched as a large capacity secondary battery recently because it has low maintenance cost, can operate at room temperature, and can independently design capacity and output.

The redox flow cell has a structure as shown in Fig. 1, and similarly to a fuel cell, a membrane, an electrode, and a bipolar plate are arranged in series to form a stack, thereby charging and discharging electric energy. It has the function of a possible secondary battery. In the redox flow cell, a positive electrode electrolyte and a negative electrode electrolyte are circulated on both sides of the membrane, and ion exchange is performed. In this process, electrons move and charge and discharge are performed. Such a redox flow battery is known to be most suitable for ESS because it has a longer lifespan than a conventional secondary battery and can be manufactured in a kW to MW class medium and large system.

Therefore, research on the redox flow battery has been made recently. Korean Patent Laid-Open Publication No. 10-2011-0119775 discloses a redox flow battery in which a cathode electrolyte and a cathode electrolyte are supplied to a battery cell having a cathode electrode, a cathode electrode, and a diaphragm interposed between these electrodes to perform charge / discharge. The anode electrolyte contains manganese ions, the cathode electrolyte contains one or more metal ions selected from titanium ions, vanadium ions, chromium ions, zinc ions and tin ions, and precipitation inhibiting means for inhibiting precipitation of MnO 2. Disclosed is a redox flow battery comprising: a. In addition, Korean Patent No. 1176126 has a plurality of battery cells composed of a bipolar plate, an electrode plate divided into a positive electrode plate and a negative electrode plate, and a membrane in series, and a plurality of stacked bipolar plates are supplied with a negative electrolyte solution and a positive electrolyte solution. In the redox flow battery structure, the bipolar plate is formed with an electrolyte inlet and an electrolyte outlet at the bottom and top, a flow path is formed between the electrolyte inlet and the electrolyte outlet, the flow path is formed, the electrolyte inlet and the electrolyte outlet On the left and right portions symmetrically in a vertical line, flow passage holes through which electrolyte having different poles pass are formed, but a short prevention tube made of an insulating material is inserted into the flow passage holes to block contact between the electrolyte solution and the bipolar plate. Prevention tube is bipolar plate exterior The redox flow battery structure is characterized in that it is condensed to the electrode plate provided on both sides of the biflo plate during lamination to prevent the electrolyte from leaking out between the bipolar plate and the electrode plate.

The efficiency of this redox flow cell is largely dependent on the separator shown in Figure 1. The separator serves as a physical barrier between the positive and negative electrolytes, and also serves as a movement path for electrons, so the electrical resistance must be low, and the mechanical properties must be secured so that it can be manufactured in a large area and applied to the stack. Conventionally, the separator is made of graphite material, so the electrical conductivity is excellent, but the manufacturing cost is high and the mechanical properties are low. As a result, there is a limit to increase the capacity of the stack, and it is a major factor that greatly increases the manufacturing cost of the redox flow battery. In Korean Patent No. 1149351, a method of manufacturing a bipolar plate for a redox flow battery, which is installed together with a protection plate, a current collecting plate, an electrode plate, and a membrane to generate electricity by a polar electrolyte solution, uses a dry cutting method of a bulk carbon material. Forming a carbon plate by marginally cutting the carbon plate, and milling and edge-processing the marginally cut carbon plate to form a body; Forming an anode electrolyte flow passage having a predetermined shape on one side of the body, and forming a cathode electrolyte flow passage on the other side of the cathode electrolyte flow passage so as not to exist on the same through shaft as the anode electrolyte flow passage; Forming respective electrolyte supply holes and electrolyte discharge holes communicating with an electrolyte supply line and an electrolyte discharge line of each of the electrolyte flow paths; Forming a coating part by coating a fluorine resin on the periphery of the body except the electrolyte supply hole and the electrolyte discharge hole and the electrolyte flow path of the body in which the electrolyte flow path, the electrolyte supply hole and the electrolyte discharge hole are formed; And inspecting and testing the entire body, the electrolyte flow path, the electrolyte supply hole, and the electrolyte discharge hole. The forming of the coating part may include inspecting the entire body to determine whether coating is possible, and then coating Masking the central portion of the body including the electrolyte flow path using a masking tape when it is determined that the operation is possible; Inspecting a peripheral portion of the body including each of the electrolyte supply hole and the electrolyte discharge hole and then degreasing using isopropyl alcohol (IPA) or distilled water; Spraying a liquid teflon primer on the periphery of the body including the electrolyte supply hole and the electrolyte discharge hole, heat-processing at a temperature of 140 to 160 ° C. for 10 to 15 minutes, and plastic coating it to lower the coating; Spraying a liquid ETFE resin on the lower coating surface to prevent heat shrinkage, heat treatment at a temperature of 300 to 400 ° C. for 10 to 60 minutes, lowering the temperature to 150 ° C., and then naturally cooling the medium to coat it; Powder coating of the ETFE powder to prevent moisture infiltration, heat treatment at a temperature of 400 ° C. for 10 to 60 minutes, lowering the temperature to 150 ° C., and then naturally cooling the phase coating; Repeating the heavy coating step and the phase coating step until the set fluororesin coating thickness is completed to complete the fluororesin powder coating; Inspecting the appearance of the coating, the thickness of the coating film, the presence of cracks, the residue oil, the scratch oil, the pin oil and the like; And it discloses a bipolar plate manufacturing method for a redox flow battery comprising the step of removing the masking tape.

By the way, the properties required for the separator plate for redox flow battery has acid resistance, electrical conductivity and mechanical properties. The separator in direct contact with a redox flow battery electrolyte made of a strong acid such as sulfuric acid should have high acid resistance and have high electrical conductivity since it becomes a passage for electrons. In addition, since the electrolyte reaction area of the redox flow battery stack needs to be larger than that of the conventional secondary battery to construct a larger capacity secondary battery, the area of the separator must be increased. Conventional graphite separators have high acid resistance and electrical conductivity, but they are easily damaged by reaction pressure or external impact when applied to large-area redox flow cell stacks due to their low mechanical properties and high brittleness. This results in a stack failure. As the area of the separator increases, the probability of breakage also increases, so the development of a large-area separator with excellent mechanical strength is essential for the production of medium-large redox flow batteries. However, in the case of the conventional separation plate (bipolar plate) including the above-mentioned document, it is difficult to fundamentally solve the above-mentioned problems, and because of the characteristics of the carbon material, the processing is not easy and there is a fear of breakage during processing, which is not preferable.

Republic of Korea Patent Publication No. 10-2011-0119775 Republic of Korea Patent No. 1176126 Republic of Korea Patent No. 1149351

Therefore, the technical problem to be achieved by the present invention is a material that can achieve the required electrical properties similar to the conventional separator plate, easy to process the shape and ensure mechanical rigidity, and lower the manufacturing cost while having durability in the electrolyte solution. It is to provide a redox flow battery separator and a redox flow battery including the separator.

In order to achieve the above technical problem, the present invention is a battery cell consisting of a pair of electrode plate divided into a positive electrode plate and a negative electrode plate, a membrane interposed between the electrode plate and the separation plate which is spaced apart from the outside of the electrode In the multiple stacked and stacked battery cells, a redox flow battery separator used in a redox flow battery that cross-feeds a cathode electrolyte solution and a cathode electrolyte solution, wherein the separator plate comprises a core part made of metal or carbon fiber and the It provides a separator plate for a redox flow battery, comprising a double structure of the graphite surface layer formed on the outside of the core portion.

The present invention also provides a separator plate for redox flow battery, characterized in that the metal is at least one single metal or alloy selected from the group consisting of Fe, Cu, Mg, Ni, Cr and Al.

In addition, the present invention is characterized in that the bonding of the core portion and the graphite surface layer is performed by a method of coating graphite on the surface of the core portion by CVD or PE-CVD or attaching the graphite layer to the core layer by adhesion. Provided is a separator for a dox flow battery.

The present invention also provides a separator plate for a redox flow battery, wherein the graphite surface layer has a thickness in the range of 10 to 500 micrometers.

In another aspect, the present invention provides a separator plate for redox flow battery, characterized in that the core before coupling the core portion and the graphite surface layer to form a surface roughness on the surface.

In another aspect, the present invention is characterized in that the surface roughness is formed by performing a mechanical surface treatment method of sand paper treatment or sand blasting (Sand blasting) or chemical surface treatment of an acid treatment. To provide.

In addition, the present invention provides a redox flow battery including the separator plate for the redox flow battery.

The present invention provides a dual-layered redox flow battery separator in which a core portion made of metal or the like and a carbon surface layer is formed on the outer surface of the core portion. Mechanical rigidity can be secured and manufacturing costs can be lowered while the electrolyte is durable.

1 is a schematic structural diagram for explaining the structure of a redox flow battery
Figure 2 is an exploded perspective view for explaining the internal structure of a conventional redox flow battery
3 is a cross-sectional view schematically showing the structure of a unit cell of a redox flow battery according to the present invention.
Figure 4 is an exploded perspective view and a partially enlarged cross-sectional view showing the internal structure of the redox flow battery according to the present invention
Figure 5 is a cross-sectional structure showing a structure of a separator plate for a redox flow battery according to an embodiment of the present invention
Figure 6 is a cross-sectional structure showing a structure of a separator plate for a redox flow battery according to another embodiment of the present invention

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

The separator plate 100 for a redox flow battery of the present invention includes a pair of electrode plates divided into a positive electrode plate 11 and a negative electrode plate 12, a membrane 10 interposed between the electrode plates, and the electrode plate ( A plurality of battery cells composed of separator plates 20 spaced apart from the outside of 11 and 12 are stacked in series, and the stacked battery cells are used in a redox flow battery that cross-feeds a negative electrolyte solution and a positive electrolyte solution. In the present specification, the structure of the redox flow battery 100, such as an electrode, a membrane, an electrolyte, and the other components except the separator 20, all of those skilled in the art will be well aware of the present invention. This will not be described separately in the specification.

Figure 5 is a cross-sectional view showing the structure of the separator 20 for redox flow battery according to an embodiment of the present invention. As shown in FIG. 5, the separator 20 for redox flow battery according to the present invention has a double portion of a core part 21 made of metal or carbon fiber and a graphite surface layer 22 formed outside the core part 21. It is structured. The metal has very high mechanical rigidity, high ductility, and almost no brittleness, so the workability is also very good, so it is easy to manufacture and process in the shape desired by the user. However, except for some precious metals, metal materials are weak in acid resistance, and carbon fibers are also inferior in acid resistance. In the present invention, the above problem can be solved by coating the surface of the core part 21 with graphite having excellent electrical conductivity and acid resistance. The type of the metal is not particularly limited, as long as it can satisfy the physical properties required for the separator as described above. Preferred examples of the metal are at least one single metal or alloy selected from the group consisting of Fe, Cu, Mg, Ni, Cr and Al.

The combination of the core portion 21 and the graphite surface layer 22 may be performed by forming graphite by CVD or PE-CVD or attaching the graphite layer 22 to the core portion 21 by an adhesive. The core portion 21 and the surface layer 22 may be formed by bonding to each other, but in general, since the electrical conductivity is inferior due to the characteristics of the polymer adhesive used for the bonding, the core portion 21 and the surface layer 22 are secured. It is preferable that only a portion of the silver is bonded or unbonded as shown in FIG. 5 or FIG. 6.

6 is a cross-sectional structural view showing the structure of a separator 20 for a redox flow battery according to another embodiment of the present invention. When the separation plate 20 is manufactured by partially bonding the core portion 21 and the graphite surface layer 22, electricity may flow by minimizing the bonding area between the core portion 21 and the surface layer 22 as shown in FIG. 6. It is important to widen the effective area. In addition, a separate surface treatment may be applied to form a constant surface roughness in each material in order to increase the contact area between the core portion and the surface layer to lower the electrical contact resistance. The surface treatment may include sand paper treatment and sand blasting as a mechanical surface treatment method, and acid treatment as a chemical surface treatment method. In addition, by applying flame treatment and plasma treatment, the contact resistance between the two materials can be lowered by effectively removing contaminants present on the surface of each material.

The thickness of the graphite surface layer 22 is not particularly limited, but the thickness of the graphite surface layer 22 is appropriate to perform the role of the separator 20 and the metal of the core portion 21 is not eroded or dissolved by the influence of the electrolyte. It is desirable to ensure thickness or more. In view of the above, it is preferable that the thickness of the graphite surface layer 22 is 10 micrometers or more. In addition, since the thickness of the graphite surface layer 22 does not need to be thicker than necessary, it is preferable from an economic point of view that it is formed below 500 micrometers. Therefore, the thickness of the graphite surface layer is more preferably in the range of 10 to 500 micrometers.

In addition, when the core portion 21 and the graphite surface layer 22 are not bonded, as shown in FIG. 6, the core portion 21 and the graphite surface layer 22 are used to effectively mount the separating plate 20 in a stack structure. It is important to join a portion of) and a portion of frame 30. In this case, it is preferable to form a step in a part of the frame 30 so that the core portion 21 and the graphite surface layer 22 do not deviate from the position.

The embodiments of the present invention described above should not be construed as limiting the technical idea of the present invention. The scope of protection of the present invention is limited only by the matters described in the claims, and those skilled in the art will be able to modify the technical idea of the present invention in various forms. Accordingly, such improvements and modifications will fall within the scope of the present invention as long as they are obvious to those skilled in the art.

11: positive electrode plate 12: negative electrode plate
10: membrane 20: separation plate
21: core part 22: graphite surface layer
30: frame 40: adhesive
50, 60: electrolyte tank 70: pump
100: redox flow battery

Claims (6)

A plurality of battery cells comprising a pair of electrode plates divided into a positive electrode plate and a negative electrode plate, a membrane interposed between the electrode plate and a separator plate spaced apart from the outside of the electrode are laminated in series, In the separator plate for a redox flow battery used in a redox flow battery that cross-feeds a cathode electrolyte and a cathode electrolyte,
The separator comprises a double structure of a core part made of metal or carbon fiber and a graphite surface layer formed on the outside of the core part. The method of claim 1,
Wherein the metal is Fe, Cu, Mg, Ni, Cr and Al, redox flow battery separator, characterized in that at least one single metal or alloy selected from the group consisting of. The method of claim 1,
The coupling of the core portion and the graphite surface layer is performed by a method of coating graphite on the surface of the core portion by CVD or PE-CVD or attaching the graphite layer to the core layer by adhesion. plate. The method of claim 1,
The graphite surface layer is a separator plate for redox flow battery, characterized in that having a thickness in the range of 10 ~ 500 micrometers. The method of claim 3,
Separating plate for a redox flow battery, characterized in that the core before coupling the core portion and the graphite surface layer surface roughness formed on the surface. Redox flow battery comprising the separator plate for redox flow battery of any one of claims 1 to 5.

Images