JPH02195657A - Electrolyte circulation type secondary battery - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention relates to an electrolyte circulation type secondary battery,
In particular, the present invention relates to an improved electrolyte circulation type secondary cell that increases battery capacity and improves battery performance.

[Prior Art] Since electrical energy is difficult to store in its original form, it must be converted into a storable energy form. On the other hand, in order to provide a stable power supply, it is necessary to supply (that is, generate power) in accordance with the power demand. For this reason, electric power companies always construct power generation facilities that meet the maximum demand and generate power in response to demand. However, as shown by the power demand curve A in FIG. 2, 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 electricity during off-peak hours (corresponding to the portion indicated by This means that only a substantially constant amount of power (an amount corresponding to the broken line Z in FIG. 2) needs to be generated at all times. If such load leveling can be achieved, it will be possible to reduce the number of power generation facilities, and it will also be possible to 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 environmental restrictions on location. There's a problem. Therefore, there is a desire to develop a new power storage technology to replace pumped storage power generation, and the development of redox flow batteries is currently underway as one such technology.

FIG. 3 is a schematic configuration diagram showing an example of a redox flow battery that has already been proposed. 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 type because it uses two tanks 3.4. The inside of the cell 2 is partitioned by a diaphragm 5 made of, for example, an ion exchange membrane, and -
The blade side constitutes a positive electrode cell 2a1, and the other side constitutes a negative electrode cell 2b.

A positive electrode 6 and a negative electrode 7 are arranged as electrodes in the positive electrode cell 2a and the negative electrode cell 2b, respectively.

In the redox flow battery 1 shown in FIG. 3, an aqueous solution of ions whose valences change, such as iron ions and chromium ions, is stored in a tank 3.4, and pumps P,
, P2, the liquid is sent to the flow type electrolytic cell 2, and charging and discharging are performed by an oxidation-reduction reaction.

For example, pe*+/pe2+ hydrochloric acid solution as the positive electrode liquid,
When Cr"/Cr"+hydrochloric acid solution is 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.

The positive electrode cell 2a of the cell 2 and the positive electrode liquid tank 3 are connected by a first conduit 11 and a second conduit 12. On the other hand, similarly for the negative electrode liquid tank 4, the third conduit 13
and a fourth conduit 14. The positive electrode liquid tank 3 and the negative electrode liquid tank 4 each store a positive electrode liquid and a negative electrode liquid as reaction liquids, and the reaction liquid feeding means provided in the first conduit 11 and the third conduit 13 serve as reaction liquid feeding means. It is supplied into the cell 2 by pumps P, , P2. The supplied catholyte and anode liquid react in the cathode cell 2a and anode cell 2b, and the reacted liquid passes through the second conduit 12 and fourth conduit 14 to the cathode liquid tank 3 and the anode, respectively. The liquid is returned to the liquid tank 4.

A conventional redox flow battery is configured as described above. However, there were problems as described below. 4A and 4B are partially cutaway front views showing reaction states within the cell during charging and discharging in the conventional redox flow battery shown in FIG. 3. FIG. 4th A
As shown by arrows A...D in the figures and FIG. 4B, in the conventional redox flow battery, as the charging operation and discharging operation are repeated, the positive electrode active material and the negative electrode active material permeate through the diaphragm 2, and as a result, There was a drawback that the amount of electrode active material in the positive and negative electrode liquids decreased, resulting in a decrease in the amount of power stored and a decrease in charging and discharging efficiency.

In order to overcome this drawback, the inventors have already proposed a so-called one-component electrolyte system technology in which a negative electrode active material is introduced into the positive electrode and a positive electrode active material is also introduced into the negative electrode (
Utility Model Application Publication No. 1983-170).

According to this method, electrode reactions are carried out at the positive electrode and the negative electrode, respectively, according to the following equations.

The electrolyte before charging contains Fe2+ as the positive electrode active material.
Since it contains equimolar amounts of Cr"+ and Cr"+ as the negative electrode active material, mass transfer through the diaphragm within the cell is effectively prevented, and therefore the concentration of each electrode active material in the positive electrode cell and the negative electrode cell is In other words, as shown in FIG. 5A, which is a schematic front view of the inside of the cell 22 during charging operation, the mass transfer indicated by arrows A and B hardly occurs. Similarly, during the discharge operation, almost no mass transfer across the diaphragm 25 occurs, and therefore, as shown in a schematic front view in FIG. 5B, mass transfer in the directions indicated by arrows C and D during the discharge operation. does not occur.

[Problems to be Solved by the Invention] The conventional method for improving redox flow batteries is as described above. However, in the one-component electrolyte system described above, there are cases where it is not possible to completely prevent the electrolyte from moving through the diaphragm, and in such cases, it is necessary to move the electrolyte after stopping the discharge and return it to the initial state. operations were being carried out.

However, this operation was not only complicated, but also did not provide any essential solution, nor was it a permanent solution.

This invention was made to solve the above-mentioned problems, and aims to provide an electrolyte circulation type secondary battery that is easy to operate, increases battery capacity, and improves battery performance. purpose.

[Means for Solving the Problems] This invention provides a positive electrode and a negative electrode separated by a diaphragm, a positive electrode liquid tank for storing a positive electrode electrolyte containing a positive electrode active material, and a negative electrode liquid tank for storing a negative electrode electrolyte containing a negative electrode active material. and feeding the cathode electrolyte to the cathode while circulating the cathode electrolyte between the cathode and the cathode tank,
On the other hand, the present invention relates to an electrolyte circulation type secondary battery in which the negative electrode electrolyte is circulated between the negative electrode and the negative electrode tank, and the negative electrode electrolyte is fed to the negative electrode for charging and discharging. In order to achieve the above object, an electrolyte amount detection means for detecting the amount of at least one of the circulating positive electrode electrolyte and negative electrode electrolyte, and an electrolyte amount detection means based on the information obtained by the electrolyte amount detection means. and an electrolytic solution feeding pressure adjusting means for adjusting at least one of the feeding pressure of the positive electrode electrolyte to the positive electrode and the feeding pressure of the negative electrode electrolyte to the negative electrode.

[Operation] As mentioned above, when the positive electrode electrolyte and the negative electrode electrolyte are sent to the battery cell, the liquid moves from one electrode to the other through the diaphragm due to the difference in the sending pressure between the two electrodes. Sometimes.

The amount of movement of this liquid is determined by detecting the amount of at least one of the circulating positive electrode electrolyte and negative electrode electrolyte using an electrolyte amount detection means. Based on the amount of movement of this liquid, at least one of the feeding pressure of the positive electrode electrolyte to the positive electrode and the feeding pressure of the negative electrode electrolyte to the negative electrode is adjusted by the electrolytic solution feeding pressure adjusting means (i.e., the liquid volume The liquid can be moved in the opposite direction through the diaphragm by increasing the liquid delivery pressure at the increasing pole, or by decreasing the liquid delivery pressure at this counter electrode, etc.). By repeating these operations, the amount of bipolar fluid can always be maintained at the initial amount.

[Example] Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic configuration diagram showing an example of a redox flow battery according to an embodiment. This redox flow battery 1 includes a cell 2, a positive electrode liquid tank 3, and a negative electrode liquid tank 4. The inside of the cell 2 is partitioned by a diaphragm 5 made of, for example, an ion exchange membrane, with the -blade side forming a positive electrode cell 2a and the other side forming a negative electrode cell 2b. A positive electrode 6 and a negative electrode 7 are arranged as electrodes in the positive electrode cell 2a and the negative electrode cell 2b, respectively. A hydrochloric acid solution of ions whose valences change, such as iron ions and chromium ions, is stored in the tanks 3 and 4, and is fed into the cell 2.

The positive electrode cell 2a of the cell 2 and the positive electrode liquid tank 3 are connected by a first conduit 11 and a second conduit 12. On the other hand, similarly for the negative electrode liquid tank 4, the third conduit 13
and a fourth conduit 14. The positive electrode liquid tank 3 and the negative electrode liquid tank 4 each store a positive electrode liquid and a negative electrode liquid as reaction liquids, and the reaction liquid feeding means provided in the first conduit 11 and the third conduit 13 serve as reaction liquid feeding means. It is supplied into the cell 2 by pumps P, , P2. The supplied catholyte and anode liquid react in the cathode cell 2 and anode cell 2b, and the reacted liquid passes through the second conduit 12 and the second conduit 14 to the cathode liquid tank 3 and the anode liquid, respectively. It is returned to the tank 4.

The above configuration is the same as the configuration of the conventional redox flow battery shown in FIG. 3, but the redox flow battery differs in the following points. That is, the first conduit 11 and the third
A pressure gauge 15 is provided in each of the conduits 13, and the second
A pressure gauge 15 is provided in the conduit 12 and the fourth conduit 14. The redox flow battery also includes a pump P,
The pump P2 includes a first electrolytic solution feeding pressure adjusting means 17 that adjusts the output of the pump P2, and a second electrolytic solution feeding pressure adjusting means 18 that adjusts the output of the pump P2. Furthermore, the tank 3 is equipped with a first liquid level gauge 19 that automatically measures the amount of electrolyte in the tank 3,
Tank 4 is a second tank that automatically measures the amount of electrolyte in tank 4.
It is equipped with a liquid level gauge 20. The first liquid level gauge 19 and the second liquid level gauge 20 are connected to a microcomputer 21, and the microcomputer 21 is connected to the first electrolytic solution feeding pressure regulating means 17 and the second electrolytic solution pressure regulating means 18. has been done.

According to this device, for example, a diaphragm 5 is connected from the negative electrode 7 to the positive electrode 6.
When the electrolyte moves through the positive electrode liquid tank 3, the first liquid level gauge 19 detects an increase in the amount of liquid in the positive electrode liquid tank 3. First liquid level gauge 1
The information detected by 9 is sent to the microcomputer 21, and at this time, the microcomputer 21 controls the first electrolyte feeding pressure regulating means 17 to increase the output of the pump P.
instruct. When the output of the pump P increases, the electrolyte moves from the positive electrode 6 to the negative electrode 7 through the diaphragm 5. Therefore, the amounts of both liquids can be maintained at the initial amounts. In this case, the microcomputer 21 may instruct the second electrolyte feeding pressure adjusting means 18 to lower the output of the pump P2.

Similarly, when the electrolyte moves from the positive electrode 6 to the negative electrode 7 through the diaphragm 5, the second liquid level gauge 20 detects the negative electrode liquid tank 4.
Detects an increase in the amount of liquid. The upper part of the second liquid level gauge 20 is sent to the microcomputer 21, and at this time, the microcomputer 21 instructs the second electrolytic solution feeding pressure adjusting means 18 to increase the output of the pump P2. Pump P
When the output of 2 increases, the electrolyte moves from the negative electrode 7 to the positive electrode 6 through the diaphragm 5. Therefore, the amounts of both liquids can be maintained at the initial amounts. In this case as well, the microcomputer 21 may instruct the first electrolytic solution feeding pressure adjusting means 17 to lower the output of the pump P.

Specifically, 10 cells each having an electrode area of 1500 cm2 were stacked to form a battery with an output of 500 W, and the redox flow battery shown in FIG. 1 was fabricated. The flow rate is 4~ for both poles.
The pressure was about 5 fL/min and the pressure was about 0.5 to 0.6 kg/cm2, but depending on the balance of the liquid levels in both tanks, the pressure would differ by about 0.05 to 0.1 kg/cm2. observed.

As a result of continuous operation for about a month, there was almost no difference in the liquid levels of both tanks compared to the initial state.

In addition, in the above embodiment, the case where the liquid level gauge and the electrolytic solution feeding pressure adjusting means are provided on both the positive electrode side and the negative electrode side is illustrated, but
This invention is not limited to this, and may be provided only on one side.

Further, in the above embodiments, the case where the present invention is applied to a redox flow type secondary battery is illustrated, but the present invention is not limited to this.

Further, in the above embodiments, a redox flow type secondary battery is exemplified in which the positive electrode liquid contains only the positive electrode active material and the negative electrode liquid contains only the negative electrode active material, but the present invention is not limited to this. Even in the case of a redox flow type secondary battery containing counter electrode active material ions in each of the negative electrode liquid and the negative electrode liquid, the same effects as in the example can be achieved.

This invention has been described above with reference to specific examples, but
The preferred embodiments described herein are illustrative and not restrictive. The scope of the present invention is indicated by the claims, and all modifications that come within the meaning of the claims are intended to be included in the present invention.

[Effects of the Invention] As explained above, according to the present invention, when the positive electrode electrolyte and the negative electrode electrolyte are fed to the battery cell, the diaphragm is transferred from one electrode to the other due to the liquid feeding pressure difference between the two electrodes. Even if the liquid may move through the electrode, the amount of movement of this liquid can be determined by detecting the amount of at least one of the circulating positive electrode electrolyte and negative electrode electrolyte with an electrolyte amount detection means. . Based on the information obtained by the electrolyte amount detection means, at least one of the pressure for feeding the positive electrolyte to the positive electrode and the pressure for feeding the negative electrolyte to the negative electrode is adjusted by the electrolyte feeding pressure adjusting means. This allows liquid to move in the opposite direction through the diaphragm.

By repeating these operations, the amount of bipolar fluid can always be maintained at the initial amount. As a result, it is possible to avoid the phenomena observed in conventional redox flow batteries, that is, the decrease in battery capacity and the deterioration of battery performance due to imbalance in liquid volume. In addition, since the liquid volume can be automatically balanced, the operation becomes easy.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of an electrolyte circulation type secondary battery according to an embodiment of the present invention. FIG. 2 is a diagram showing a power demand curve. FIG. 3 is a schematic configuration diagram showing an example of a conventional redox flow battery. 4A and 4B are schematic partially cutaway front views showing reaction states during charging and discharging operations in the cells of the conventional redox flow battery shown in FIG. 3. FIG. Fifth
FIG. A and FIG. 5B are diagrams showing reaction states during charging and discharging operations in the cell of a battery employing a -molded electrolyte system. In the figure, 1 is a redox flow battery, 2a is a positive electrode cell, 2b is a negative electrode cell, 3 is a positive electrode liquid tank, 4 is a negative electrode liquid tank, 5 is a diaphragm, 6 is a positive electrode, 7 is a negative electrode, and 17 is a first electrolyte. Liquid feeding pressure adjustment means, 18 is a second electrolyte liquid feeding pressure adjustment means, 19 is a first liquid level gauge, 20 is a second liquid level gauge, 2
1 is a microcomputer. In each figure, the same reference numerals indicate the same or corresponding parts. 2nd 3rd 4A (2) 85A sword 4B 5B

Claims (3)

[Claims] (1) A positive electrode and a negative electrode separated by a diaphragm, a positive electrode liquid tank for storing a positive electrode electrolyte containing a main electrode active material, and a negative electrode liquid tank for storing a negative electrode electrolyte containing a negative electrode active material; The positive electrode electrolyte is fed to the positive electrode while circulating the positive electrode electrolyte between the positive electrode tank and the negative electrode electrolyte while circulating the negative electrode electrolyte between the negative electrode and the negative electrode tank. In an electrolyte circulation type secondary battery in which the negative electrode electrolyte is fed to the negative electrode for charging and discharging, the electrolyte amount detection means detects the amount of at least one of the circulating positive electrode electrolyte and the negative electrode electrolyte; , an electrolytic solution feeding pressure adjusting means for adjusting at least one of the feeding pressure of the positive electrode electrolyte to the positive electrode and the liquid feeding pressure of the negative electrode electrolyte to the negative electrode based on the information obtained by the electrolytic solution amount detecting means; An electrolyte circulation type secondary battery comprising: and. (2) the battery is a redox flow type secondary battery;
An electrolyte circulation type secondary battery according to claim 1. (3) The electrolyte circulation type secondary battery according to claim 2, wherein the positive electrode electrolyte and the negative electrode electrolyte each contain counter electrode active material ions.