JPS614169A - Redox flow battery - Google Patents

Abstract

PURPOSE:To reduce contact resistance and eliminate unevenness of internal resistance by forming positive and negative poles constituting a cell of a redox flow battery by interposing expansive graphite layers between current collecting electrodes and reactive electrodes. CONSTITUTION:Reactive electrodes 16, 17 made of porous carbon electrode are disposed on both sides of a diaphragm 5 made of ion exchange film and expansive graphite layers 22, 23 of rich flexibility, restoration ability and sealing ability are provided on both the sides of the electrodes, and current collecting electrodes 18, 19 made of graphite plate are arranged on both the sides of the layers to form a cell 2, and plural cells are connected in series to form a cell stack of a redox flow battery. Then contact resistance between the reactive electrodes 16, 17 and current collecting electrodes 18, 19 can largely be reduced by using expansive graphite layers 22, 23 and unevenness of internal resistance among respective cells can be eliminated to obtain a battery of excellent power efficiency.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention This invention relates to an improvement in the structure of a redox flow battery for power storage, and more particularly to a redox flow battery with an improved electrode structure.

BACKGROUND OF THE INVENTION Electrical energy is difficult to store in its raw form and must be converted into a storable form of energy. On the other hand, in order to provide a stable power supply, it is necessary to supply or generate power in accordance with the power demand. For this reason, electric power companies always produce electricity that meets maximum demand! We are constructing facilities and generating electricity in response to demand. However, as shown by the power demand curve in FIG. 3, there is a large difference in power demand during the day and at night. Similar phenomena occur across weeks, months, and seasons.

Therefore, if it is possible to store electricity efficiently,
By storing surplus power during off-peak hours (corresponding to the portion indicated by power, which is always almost constant (as shown by the broken line Z in Figure 3).
Therefore, it is only necessary to generate electricity in an amount equivalent to . If such leveling can be achieved, the power generation equipment can be reduced, and it can greatly contribute to energy savings and fuel savings such as oil.

Therefore, various power storage methods have been proposed.

For example, pumped storage power generation has already been implemented, but with pumped storage power generation, the equipment is installed far away from the consumption area, resulting in transmission and substation losses, and there are also environmental restrictions on location. There is. Therefore, there is a desire to develop a new power storage technology to replace pumped storage power generation, and redox flow batteries are being developed as one of these technologies.

FIG. 4 shows a schematic configuration diagram of an example of a redox flow battery. This redox flow battery 1 includes a cell 2, a positive electrode liquid tank 3, and a negative electrode liquid tank 4, and is called a two-tank system because it uses two tanks 3 and 4. The inside of the cell 2 is partitioned by a diaphragm 5 made of, for example, an ion exchange membrane, and a positive electrode 6 and a negative electrode 7 are arranged as electrodes in the positive electrode cell 2a on one side and the negative electrode cell 2b on the other side, respectively.

In the redox flow battery 1 shown in FIG. 4, an aqueous solution of ions whose valences change, such as iron ions and chromium ions, is stored in tanks 3 and 4, and pumped to the pump P.
7. At P2, the liquid is sent to the flow-through electrolytic cell 2, and charging and discharging are performed by an oxidation-reduction reaction.

For example, Fe 8 + / Fe 2 as a catholyte
When +hydrochloric acid solution and Or2''10r3+hydrochloric acid solution are used as the negative electrode liquid, the battery reaction at both electrodes 6 and 7 of each redox system is as shown in the following equation, and the electromotive force is about 1V.

To begin with, the cell 2 shown in the schematic diagram in FIG. It has a cell structure in which current collecting electrodes 18 and 19 are clamped and clamped from both sides. Note that, as shown in the figure, a plurality of cells 2 shown in FIG. 5 are connected in series via current collecting electrodes 18 and 19.

By the way, in FIG. 5, reference numeral 20.21 indicates a packing provided around the porous carbon electrode 16.17. For reference, FIG. 6 shows the specific structures of the current collecting electrode 18, the porous carbon electrode 16, and the packing 20.

In the conventional cell structure shown in FIGS. 5 and 6, a porous carbon electrode, for example, is used as the reaction electrode 16.17, and a graphite plate is used as the current collecting electrode 18.19. ing. The reaction electrodes 16, 17 made of such materials and the current collecting electrodes 18, 19 made of graphite plates were simply contacted by pressure bonding. Therefore, the electrical resistance at the contact surface tends to vary, and as a result, the internal resistance varies from cell to cell, and even for a single cell,
Furthermore, stack cells connected in series also have the disadvantage that their performance varies and the overall charging/discharging power efficiency decreases.

, Problems to be Solved by the Invention Therefore, the object of the invention is to overcome the above-mentioned drawbacks and
The object of the present invention is to provide a redox flow battery that reduces contact resistance between a reaction electrode and a current collection electrode, effectively eliminates variations in internal resistance of each cell, and has excellent power efficiency.

11 U IJL Means for Solving the Problems In summary, the present invention provides a redox flow battery having a cell structure in which positive and negative reaction electrodes separated by a diaphragm are clamped from both sides by current collecting electrodes. A redox flow battery is characterized in that an expanded graphite layer is provided between a current collecting electrode and a reaction electrode.

That is, in addition to the conventional cell structure, this invention attempts to solve the above problems by interposing expanded graphite, which is highly flexible, resilient, and sealable, between the reaction electrode and the current collecting electrode. It is something to do.

Embodiment FIG. 1 is a sectional view showing an embodiment of the present invention. In this embodiment, a plurality of cells 2 are connected in series, thus forming a stacked cell. The feature of this embodiment is that an expanded graphite layer 22.23 is provided between the current collecting electrode 1.8.19 made of a graphite plate and the reaction electrode 16.17 made of a porous carbon electrode. be. As described above, the expanded graphite layers 22 and 23 are highly flexible, resilient, and sealable. Therefore, by crimping the current collecting electrodes 18 and 19 from both sides,
The reaction electrode 16.17 and the expanded graphite layer 22.23, as well as the current collection electrode 18.19 and the expanded graphite layer 22.23 are effectively brought into close contact. It goes without saying that the expanded graphite layer has high conductivity. Therefore, the reaction electrode 16.
It can be seen that the contact resistance between 17 and the expanded graphite (lead layers 22 and 23) and the contact resistance between the expanded graphite layers 22 and 23 and the reaction electrodes 18 and 19 are extremely small. It is possible to reliably reduce variations in internal resistance of each cell 2 in a stacked cell.

Next, specific experimental examples will be described. As shown in the exploded perspective view of FIG. 2, rubber gaskets 20.
Reaction electrode 16.17 consisting of carbon cloth surrounded by 21
was placed, expanded graphite layers 22 and 23 were placed on the outside thereof, and current collecting electrodes 18 and 19 made of graphite plates were placed on the outside thereof, and then all the pads were crimped to form a cell. . Note that the electrode area is 1×100rr12. When we checked the charge/discharge efficiency using the cells configured in this way, we found that although we made 5 to 6 prototype cells with the same structure, we did not see any variation in power efficiency among the cells, which was the case in the past. It was confirmed that the discharge efficiency was improved by at least 5% on average.

11.IL As described above, according to the present invention, since the expanded graphite layer is provided between the current collecting electrode and the reaction electrode, l1 MII! Since the cell is formed by crimping the reaction electrodes separated by J through the expanded graphite layer, it is possible to reliably eliminate variations in internal resistance for each cell, thereby improving reliability. It becomes possible to realize an excellent redox flow battery. Furthermore, when used in a stacked cell, it is possible to improve charging and discharging efficiency.

The present invention can be applied not only to the illustrated II cell but also to redox flow batteries for power storage in general.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an embodiment of the present invention. FIG. 2 is an exploded perspective view of a cell used in a specific experimental example of the present invention. FIG. 3 is a diagram showing a power demand curve. FIG. 4 is a schematic configuration diagram showing an example of a redox flow battery. FIG. 5 is a cross-sectional view showing an example of the cell structure of a conventional redox flow battery. 6 is a perspective view showing a current collecting electrode and a reaction electrode used in the cell structure shown in FIG. 5. FIG. In the figure, 5 is a diaphragm, 16.17 is a reaction electrode, 18.
Reference numeral 19 indicates an N-collecting electrode, and reference numerals 22 and 23 indicate expanded graphite layers. Figure 1 Figure 2 Figure 4

Claims (3)

[Claims] (1) In a redox flow battery having a cell structure in which positive and negative reaction electrodes separated by a diaphragm are clamped from both sides by current collecting electrodes, expanded graphite is placed between the current collecting electrode and the reaction electrode. A redox flow battery characterized by having layers. (2) The redox flow battery according to claim 1, wherein the reaction electrode is a porous carbon electrode. (3) The redox flow battery according to claim 1 or 2, wherein the current collecting electrode is made of a graphite plate.