JPS58176880A - Operation control method of redox-flow type battery - Google Patents

Abstract

PURPOSE:To make an electrolytic reaction perform, by separating a charging solution from a discharge solution as in two layer parts inside a tank and feeding both solutions in accordance with the case in times of charging and discharging when letting an electrolyte flow into a battery body from both anode and cathode solution tanks. CONSTITUTION:After an electrolyte extracted from tanks 1 and 2 is reacted inside an electrolyte-flow type battery, the electrolyte is returned to these tanks by pumps 3A and 3B, and charging or discharging is carried out. At this time, these tanks 1 and 2 are set down to an electrolyte tank 10 installing valves 13A, 13B for inflow and outflow of the electrolyte at its upper part as well as valves 14A, 14B for inflow and outflow of the electrolyte at its lower part respectively and, by reason that specific gravity in the electrolyte varies with charging and discharging conditions, such an electrolyte as being separated into two layer parts, upper and lower layers, inside the tank is extracted and fed to a battery body 4. Therefore, an electrolytic reaction can be achieved in high voltage efficiency in an easy manner by making full use of a phenomenon of what is known as an electrolyte two-layer separation.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of operating a redox flow battery,
More specifically, the present invention relates to an efficient method of operating a secondary battery of an electrolyte flow type battery.

An electrolyte flow type battery is a battery in which the electrolyte flows into the battery and the battery reactions of charging and discharging occur while the electrolyte flows out.The electrolyte is a catholyte that causes a more anodic battery reaction. , and negative electrode liquid, which causes a more cathodic battery reaction. If the positive and negative electrode liquids are made of oxidizing and reducing substances, that is, substances in which oxidation and reduction reactions can occur reversibly, this battery can be used as a secondary battery.

Conventionally proposed electrolyte flow type secondary battery systems use a hydrochloric acid acidic iron chloride aqueous solution as the positive electrode liquid, and a hydrochloric acid acidic chromium chloride aqueous solution as the negative electrode liquid. In this case, an inert electrode such as carbon is mainly used as the electrode of the electrolyte flow type battery, and its theoretical charging voltage and theoretical discharging voltage are expressed by the following Nern equation.

Here, E indicates the theoretical voltage, % (Cr”) is trivalent chromium, (Fe2”) is divalent iron, (Cr”) is divalent chromium,
(Fe33) indicates the concentration of trivalent iron.The higher the concentration of trivalent chromium and divalent iron, the lower the charging voltage can charge the battery, and conversely, the higher the concentration of trivalent chromium and divalent iron, the lower the charging voltage. The higher the concentration of trivalent iron, the greater the discharge voltage that can be generated, and the higher the voltage efficiency in charging and discharging the battery.

Figure 1 shows an ideal battery system with the highest voltage efficiency during charging and discharging.It is called the four-tank method because the electrolyte after charging and discharging is separated and stored in tanks. There is. In the figure, the packaging system includes a cathode liquid tank IA,
IB, negative electrode liquid tanks 2A, 2B, circulation pump 3A,
3B, battery number, and electrolyte switching valve 5A! 5
The substation 7 is connected to a power plant 8 and a demand side 9.

In the above system, in order to carry out the four-tank method efficiently, one and two people must have nearly 100 tanks of charged electrolyte (in the above case, the positive electrode In the liquid tank IA, it is almost trivalent iron, and in the negative electrode liquid tank 2A
The tanks IB and 2B, which store the electrolyte after discharge (which is almost divalent chromium), and the electrolyte that should be discharged at nearly 1oO% (divalent iron in tank 1B and trivalent chromium in tank 2B) It is desirable to store chromium). To do this, nearly 100% of the reactants (trivalent chromium and divalent iron during charging in the above example) must be reacted when passing through the electrodes, which means that the reactant capture rate of the battery must be reduced to 100%. %, but in order to keep the shape of the electrode (size such as length) and pressure loss during electrolyte permeation within the electrode within a practically preferable range,
The reactant capture rate must be reduced to a few tens of percent at most. Therefore, it is not preferable to perform a charge/discharge reaction on a battery with an excessive amount of electrolyte, and although the four-tank method has the advantage of high charging/discharging voltage efficiency in principle, it is not suitable for the battery system of the above example. The problem is that it is not suitable.

On the other hand, there is a battery active material storage method called the Nitank method, as shown in Figure 2, in which the electrolyte extracted from the tank 1.2 is reacted in the battery 4, and then pumped again using the pump 3. It is returned to the original tank. At this time, the electrolyte before and after the battery reaction is mixed, and the concentration of charge or discharge reactants in the electrolyte decreases, but the amount of electrolyte sent to the battery is increased to maintain the necessary current density. By adopting an electrolyte recycle method for the battery, the reaction material capture rate can be maintained for about 7 km.

However, the Nitank method battery system also has the following drawbacks. That is, when there is a difference in specific gravity between the electrolytic solution after charging and the electrolytic solution after discharging, the three usually do not mix in the tank and separate into two layers. At this time, if there is only one electrolyte extraction hole from the tank, only one of the two layers of liquid will be extracted, and the concentration of reactants in the battery will significantly increase during either charging or discharging. It manifests itself in causing shortages. To explain this phenomenon for the positive electrode solution in the above example, trivalent iron has a higher specific gravity than divalent iron in the hydrochloric acid acidic iron chloride aqueous solution, and in the Nitank method, the electrolyte after charging is separated from the electrolyte after discharging. It is separated and stored at the bottom of tank 1. Since the electrolyte extraction hole of the tank 1 is located at the bottom of the tank 1, the discharging reaction of the battery 4 progresses favorably, but the charging reaction becomes extremely difficult to proceed due to a significant lack of divalent iron. Traditionally, problems like this.

This problem has been dealt with by stirring the electrolyte in the tank, but
There are disadvantages such as a decrease in voltage efficiency due to mixing of the charging liquid and the discharging liquid, and the need for a power source for stirring. Especially in energy storage equipment such as batteries, the need for an extra power source directly leads to a decrease in energy storage efficiency.

The purpose of the present invention is to solve the problems of the Nitank method mentioned above,
Moreover, it is an object of the present invention to provide a method of operating a battery that can perform an electrolytic reaction with high voltage efficiency by making use of the phenomenon of electrolyte two-layer separation.

The present invention relates to a method of operating a battery in which charging or discharging reactions are carried out by flowing electrolyte from a positive electrode tank and a negative electrode tank through an electrolyte flow type battery body. The charging liquid and the discharging liquid are separated into two layers in the tank, and when the battery is being charged or discharged, the discharging liquid and the discharging liquid have different specific gravities. It is characterized in that the liquid is extracted and sent to the battery main body at l~.

In the present invention, in order to send one of the electrolytes separated into two layers to the battery body, (1) provide an electrolyte flow hole near the bottom of the tank and just below the liquid level in the nuclear tank. (2) Directly below the liquid level in the tank and near the bottom of the tank, respectively, and switch the flow direction of the electrolyte to the electrolyte flow hole during charging and discharging. (3) The electrolytic solution is extracted from one of the holes dedicated to wrinkle flow and sent to the battery body during charging and discharging.
It is sufficient to extract the liquid through a flexible pipe having a float and send it to the battery body.

Hereinafter, the present invention will be explained in more detail with reference to the drawings.

FIG. 3 is a cross-sectional view of an electrolyte tank for explaining the present invention in detail. In FIG. . As mentioned above, this is due to the difference in specific gravity between the electrolyte in a charged state and the electrolyte in a discharged state, and in order to mix them uniformly in a tank as in the past, a stirring operation is required. is necessary. In the present invention, in order to reversely utilize this separated electrolyte, there are two liquid extraction holes at the top and bottom of the tank.
3 and 14 are provided, and the liquid in the discharged state (discharge liquid) and the liquid in the charged state (charged liquid) separated into the upper and lower parts are extracted and sent to the battery body, and used as a highly concentrated charge or discharge reaction material. be.

Next, FIG. 4 shows a case where a semi-floating type partition plate 15 that can be moved up and down in the tank is used to help separate the electrolyte in the charged state and the discharged state.

This partition plate is made to have a specific gravity intermediate between that of the electrolytic solution in a charged state and that in a discharged state.

FIG. 5 shows an example of an apparatus system for carrying out the present invention, in which holes (valve) 13A and 13B exclusively for electrolyte inflow and outflow, respectively, are provided on the upper and lower side walls of the electrolyte tank 10. , and dedicated holes 14A and 14B for inflow and outflow 4b are also provided at the bottom of the tank. In addition,
In this figure, only the electrolyte lines 16 and 17 on the positive electrode side connecting the electrolyte tank 10 and the battery body 4 are shown, and -
The polar side is omitted as it is displayed in the same way.

In the above equipment system, the electrolyte of the battery body number is line T.
6 to the positive electrode liquid tank 10 through the valve 13A114A.
where it separates into two layers, upper and lower. When an aqueous iron chloride solution is used as the positive electrode liquid, trivalent iron is separated into the lower layer and divalent iron is separated into the upper layer.When the battery is being charged, the liquid in the upper layer is in a discharged state (divalent iron), and when discharging, the lower layer is the divalent iron. The charged liquid (trivalent iron) is extracted through the valve 13B or 14'B, respectively, and supplied to the battery body. In addition, there are two dedicated electrolyte inflow holes 13A and 114A connected to the tank.
Even if they are combined into one, it is possible to separate the electrolyte into two layers,
In reality, it is preferable to combine the inflow holes into one because the device can be simplified.

FIG. 6 shows still another embodiment of the present invention, in which inflow and outflow holes 13 and 14 are provided at the top and bottom of the tank 10 for both inflow and outflow of the electrolyte, and the inflow and outflow can be switched from all directions. This is done by the valve 18. The figure shows the state during discharge when the liquid (trivalent iron) in the lower layer of the MVi is extracted from the tank and supplied to the battery body 4 by the pump 3A. (bivalent iron) can be extracted from the tank, supplied to the battery main body 4, and used for charging.

In the present invention, the tank mounting position of the electrolyte flow hole is
There is no particular limitation as long as the upper and lower electrolytes can be separated and extracted, for example, as shown in FIG.
Using the float 19 and the flexible tube 2o, it is possible to provide the function of the electrolyte flow hole 13 in the upper part of the tank shown in FIGS. 5 and 6. According to the above configuration, even if the total electrolyte level in the tank fluctuates, the electrolyte during charging and discharging can be supplied to the battery main body with sufficient separability.

As described above, the present invention utilizes the phenomenon of electrolyte two-layer separation, which eliminates the need for a new power source for agitation or double-tracking of the battery system, and eliminates the need for a new power source for stirring, and by utilizing the phenomenon of electrolyte two-layer separation, a high concentration of charging reactants is generated during charging. and during discharge, a high concentration of discharge reactant can be sent to the battery main body to carry out an electrolytic reaction with -1 high voltage efficiency.

Example A hydrochloric acid acidic iron chloride aqueous solution was used as the positive electrode liquid, and a hydrochloric acid acidic chromium chloride aqueous solution was used as the negative electrode liquid.The positive electrode liquid side was an electrolyte flow line as shown in Fig. 5, and the negative electrode liquid side was placed in a negative electrode tank. The line was provided with an electrolyte inflow hole and an electrolyte outflow hole. Nitrogen gas was introduced into the negative electrode liquid tank to stir the electrolytic solution, and the tank was also filled with nitrogen gas to prevent the charged negative electrode liquid, that is, chromium chloride, from being oxidized by air. The positive electrode solution in the tank 10 was separated into two layers, a lower layer of trivalent iron and an upper layer of divalent iron, so the upper layer liquid was extracted during charging, and conversely, the lower layer liquid was extracted during discharging. The electrolyte was introduced into the battery body using porous carbon as an electrode and a cation exchange membrane as a diaphragm, and the electrolyte was heated to 20 mAcm.
Galvanostatic charging and discharging experiments were conducted at current densities of 1.5", 40 mAcm"s and 60 mAcm. For comparison, we also conducted a constant flow charge/discharge experiment under conditions where nitrogen gas was introduced into the cathode solution in the tank and the cathode solution was stirred.

The above experimental results (charging/discharging characteristic curve in the case of a charging depth of 50 inches) are shown in FIG. In the figure, 21 shows the case of the present invention (example), and 22 shows the case of the comparative example.

As is clear from the figure, it can be seen that the present invention greatly contributes to improving the voltage efficiency during charging and discharging of the secondary battery.

In addition, the configuration of the positive pole/return and flow line is as shown in Figures 6 and 7. The experiment also showed results similar to those shown in Figure 8.

[Brief explanation of drawings]

Figures 1 and 2 are system diagrams showing a conventional method of operating a secondary battery, respectively, and Figures 3 and 4 show the state of two-layer separation of an electrolyte tank, which is a detailed explanation of the present invention. The conceptual diagram shown in FIG. 5, FIG. 6, and FIG. 7 are a system diagram of an apparatus for explaining the present invention in detail, and FIG. 8 is a diagram showing the results of an embodiment of the present invention. 1, 1O... Electrolyte tank, 3A... Circulation pump, 11... Upper layer liquid, 12... Lower layer liquid,
13... Upper layer flow extraction hole, 13A, 13B... Same valve, 14-... Lower layer liquid extraction hole % 14A114B
...Same valve, 1st day... Four-way pulp, 19...
...Float, 20... Flexible/pull pipe. Agent Patent Attorney Takenaga Kawakita Figure 1 Figure 2

Claims (1)

[Scope of Claims] (1) In a method of operating a battery in which a charging or discharging reaction is carried out by flowing electrolyte from a positive electrode tank and a negative electrode tank through an electrolyte flowing type battery body, The liquid (charging liquid) and the liquid in the discharge state (discharging liquid) have different specific gravity, and the charging liquid and the discharging liquid are separated into two layers in the tank. A method of operating a redox flow type battery, characterized in that a liquid is extracted and sent to the battery main body. (2. In claim 1, an electrolytic solution flow hole is arranged near the bottom of the tank and directly below the liquid level in the tank, and the electrolyte solution drains during charging and discharging. A method for operating a redox flow battery, characterized in that the direction of flow of electrolyte into the holes is switched. A method of operating a redox flow battery, characterized by arranging a hole exclusively for the outflow of electrolyte solution, and drawing out the electrolyte solution from either of the holes exclusively for the outflow during charging and discharging, and sending the liquid to the battery body. ( 4')l!fFF In Claim 1, the redox flow is characterized in that the discharge liquid or charging liquid separated into two layers is extracted through a flexible pipe having a float and is sent to the battery body. How to operate a type battery.