JPH077681B2 - Metal-bromine battery clean-out method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention aims to effectively utilize an electrolytic solution by circulating the electrolytic solution between a metal-bromine battery of electrolytic solution circulation type, particularly between an electrolytic solution storage tank and a reaction tank. The present invention also relates to an electrolytic solution circulating metal-bromine battery of a type in which a predetermined charge / discharge reaction is performed.

[Prior Art] A metal-bromine battery of a type in which an electrolytic solution is circulated between an electrolytic solution storage layer and a reaction tank to perform a predetermined charge / discharge reaction, for example, zinc-
A bromine battery is known as one of new type batteries, and a basic electrochemical reaction represented by the following formula is performed in a reaction tank provided with a positive electrode and a negative electrode.

(Positive electrode) 2Br ⁻ → Br ₂ + 2e ⁻ (Negative electrode) Zn ²⁺ ＋ 2e ⁻ → Zn… (1) Charge (overall) Zn ²⁺ ＋ 2Br ⁻ Zn ＋ Br ₂ discharge As is clear from this reaction equation, it is on the negative electrode during charging. Zinc Zn is extruded on the cathode, and bromine Br ₂ is produced at the positive electrode, and this Br ₂ is dissolved in the electrolytic solution. Further, during discharge, zinc Zn extruded on the negative electrode plate is oxidized to become Zn ²⁺ and dissolved in the electrolytic solution, and bromine Br ₂ in the electrolytic solution is reduced to form bromine ions 2
It becomes Br ^- and similarly dissolves in the electrolyte.

However, such zinc - In bromine battery, is said bromine Br ₂ increases with concentration elapsed charging time in the electrolytic solution of bromine Br ₂ produced during charging diffuses gradually in the negative electrode side. Then, the bromine Br ₂ reacts with zinc Zn on the negative electrode side to form zinc ions Zn ²⁺ and bromine ions Br −, and causes self-discharge, so this zinc-bromine battery is zinc ion Zn ² Separating the reaction tank into a positive electrode side reaction tank and a negative electrode side reaction tank by using a separator film for preventing self-discharge that permeates ⁺ and bromine ion Br ⁻ and blocks bromine Br ₂ permeation, and moves from the positive electrode side to the negative electrode side Bromine Br ₂ is prevented from diffusing.

Furthermore, in the zinc-bromine battery, in order to prevent the diffusion of the bromine Br ₂ , a complexing agent is added to the electrolytic solution, and bromine Br ₂ dissolved in the positive electrode side electrolytic solution is a complex that is difficult to dissolve in the electrolytic solution. As a compound, it is separated and precipitated as an oil in the electrolytic solution.

FIG. 3 shows a conventional zinc-bromine battery formed by using such a principle. This battery is provided with a positive electrode 2 and a negative electrode 3 on both sides in a reaction tank 1 and both electrodes are provided. 2,3
The electrochemical reaction of the first formula is performed between the two via the electrolytic solution 4.

In such a zinc-bromine battery, an aqueous solution of zinc bromide (ZnBr ₂ ) is used as the electrolytic solution 4, and in addition to this, a conductivity improver, a bromine complexing agent, a dendrite suppressor, etc. are added. Has been done.

Then, at the time of charging, the charging reaction shown in the first formula is performed in the reaction tank 1, bromine Br ₂ is produced on the positive electrode 2 side and dissolved in the electrolytic solution 4, and zinc Zn is extruded on the negative electrode 3. The zinc protrusion layer 5 is formed on the negative electrode 3.

When discharging, a reaction opposite to that during charging is performed,
On the positive electrode 2 side, bromine Br ₂ is reduced to bromine ions 2Br ⁻ and dissolved in the electrolyte solution 4, and on the negative electrode 3 side, a zinc layer 5 is formed.
Is oxidized to become zinc ions Zn ²⁺ and dissolved in the electrolytic solution 4.

The inside of the reaction tank 10 in which such an electrochemical reaction is carried out is provided by the separator film 6 inside the reaction tank 10 on the positive electrode side so that bromine Br ₂ generated during charging does not cause self-discharge.
It is separated into 1a and a negative electrode side reaction tank 1b.

The separator film 6 allows the electrolytic solution 4 to permeate therethrough in order to prevent self-discharge, but prevents the permeation of bromine Br ₂ dissolved therein. As such a separator membrane 6, an ion exchange membrane or a porous membrane is generally used, but a porous membrane is used from the viewpoint of reducing the internal resistance of the battery.

In the electrolytic solution circulation type battery, a positive electrode side electrolytic storage tank 7 and a negative electrode side electrolytic solution storage tank 8 are provided in order to store energy obtained by the electrolytic reaction during charging.

The positive electrode side electrolytic solution storage tank 7 constitutes an electrolytic solution circulation path between the positive electrode side reaction tank 1a and the distribution ducts 9 and 10, and the inside of the positive electrode side reaction tank 1a is formed by a pump 11 provided in the circulation path. The positive electrode side electrolytic solution 4a that has reacted in the above is sent out to the storage tank 7,
The new electrolytic solution 4a stored in the storage tank 7 is supplied to the reaction tank 1a.

Here, when a bromine complexing agent is added to the electrolytic solution 4, bromine Br ₂ generated during charging is complexed,
The complex compound insoluble in the electrolytic solution 4 is deposited, and in the battery shown in FIG. 3, the complex compound is sequentially deposited and stored here as the complex reservoir 12 at the bottom of the storage tank 7.

A valve is provided between the complex storage unit 12 and the distribution duct 10.
It is connected by a complex supply duct 14 with 13. The valve 13 is normally opened, and the complex compound precipitated in the complex storage section 12 is passed through the distribution duct 10 to the reaction tank.
Send out for discharge toward 1a.

Similarly, the negative electrode side electrolytic solution storage tank 8 forms an electrolytic solution circulation path with the negative electrode side reaction tank 1b through the distribution ducts 15 and 16, and a pump 17 provided in the circulation path. The negative electrode side electrolytic solution 4b reacted in the negative electrode reaction tank 1b is stored in the storage tank 8
To the reaction tank 1b.
Supply to.

As described above, this zinc-bromine battery stores the electrolytic solution 4 sufficiently in the storage tanks 7 and 8, and when the stored electrolytic solution 4 is used for charging, the charging reaction shown in the first formula is performed to obtain the complex. The bromine complex compound is stored in the storage unit 12, and the zinc layer 5 is deposited on the negative electrode 3.
Can be formed to store power. Further, at the time of discharge, the complex compound of bromine stored in the complex storage section 12 is sent toward the positive electrode side reaction tank 1a, and the complex compound and the zinc layer 5 formed on the negative electrode 3 are used, The discharge reaction shown in the first formula can be performed to discharge the charging power.

Then, if you leave it after charging or during discharging,
At the same time when charging or discharging is stopped, the circulation of the electrolytic solution is stopped, and a large amount of the bromine complex compound remains in the positive electrode reaction tank 1a. In this state, since the separator membrane 6 cannot completely prevent the permeation of bromine, the bromine Br ₂ liberated from the bromine complex compound permeates the separator membrane 6 and the anode reaction tank 1
It diffuses into b and directly reacts with the zinc 5 protruding on the negative electrode 3 to cause self-discharge. Self-discharge reduces the battery capacity and causes self-heating, which shortens the battery life.

Therefore, when the battery is left as it is, it is necessary to recover (clean out) the bromine complex compound in the positive electrode reaction tank 1a to the bromine complex compound storage tank 12 in the positive electrode liquid storage tank 7.

In this clean-out, the valve 13 is closed and the electrolyte 4 is continuously circulated by the pump 11 for a certain period of time, so that the bromine Br ₂ released in the reaction tank 1a and the circulation route 9 and 10
Are collected in a storage tank.

The state of this recovery is shown in FIG. Figure 2 shows SOC (Sate
Two examples are shown when the of charge is 100% and 50%. The black dots indicate the case where the pump 11 is continuously driven for a certain period of time.

That is, it can be seen that in both cases of SOC 100% and 50%, the bromine Br ₂ in the reaction tank is recovered and the electric capacity (Ah) in the reaction tank decreases as the recovery time becomes longer.

[Problems to be Solved by the Invention] However, in the conventional clean-out method, since the pump is continuously driven for a long time, considerably large driving energy is required, and there is a problem that battery efficiency is deteriorated.

Further, since the pump is continuously driven for a long time, there is a problem that the life of the pump is shortened.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and reduces the driving energy of the pump to improve the battery efficiency while maintaining the same clean-out effect as the conventional one. It is an object of the present invention to provide a metal-bromine battery clean-out method that can be made longer than before.

[Means and Actions for Solving Problems] In order to achieve the above-mentioned object, the present invention is arranged in a step of closing a discharge valve of a storage tank for a bromine complex compound, and in the electrolytic solution circulation path after the closing step. And a step of circulating the electrolytic solution by intermittently driving the pump for a predetermined time.

By going through the steps, particularly by intermittently driving the pump, the bromine complex compound remaining in the reaction tank and the circulation route can be recovered in the complex storage tank while maintaining the same effect as the conventional one.

That is, a metal-bromine battery in which an electrolyte solution / bromine complex compound is circulated through a circulation path between an electrolyte solution storage tank and a reaction tank to perform a predetermined charge / discharge reaction, and the positive electrode side storage tank is bromine complexed. Body compound storage part in the lower part, the discharge valve capable of controlling the outflow of the bromine complex compound to the reaction tank side is in the bottom part, and the outlet of the positive electrode side electrolyte solution to the reaction tank side is in the upper part, respectively. A provided metal-bromine battery clean-out method, wherein the discharge valve is closed to prevent outflow of the bromine complex compound, and a pump disposed in the electrolyte circulation path is intermittently operated for a predetermined time. It is characterized in that the electrolytic solution is driven to circulate, and the bromine complex compound remaining in the reaction tank and the circulation path is recovered in the storage tank.

[Embodiment] A preferred embodiment of the present invention will be described below with reference to FIGS. 1 and 2. Since the basic structure of the metal-bromine battery is the same as that described in the conventional example, the description thereof will be omitted.

FIG. 1 is a diagram showing a driving state of a pump 11 that circulates the electrolytic solution 4a.

That is, like the conventional cleanout, the discharge valve 13 of the complex storage tank is closed, and after the closing, the pump 11 arranged in the electrolytic solution circulation path is driven.

At this time, as shown in FIG. 1, the pump drives the pump for 5 minutes and then stops driving the pump for the next 5 minutes. Then, driving and suspension of the pump 11 is repeated for a certain period of time. By the intermittent operation of this pump, the electrolytic solution 4a is circulated, and the reaction tank
The bromine complex compound remaining in 1a and 9 and 10 in the circulation route is recovered in the storage tank. In this case, the lower part of the positive electrode side electrolyte solution storage tank 7 constitutes the complex storage part 12 of the bromine complex compound, the upper part thereof constitutes the storage part 7a of the positive electrode side electrolyte solution 4a, and the discharge valve of the bromine complex compound. 13 is provided in the bottom portion 7b of the positive electrode side electrolyte storage tank 7 and the outlet 10a for delivering the positive electrode side electrolyte solution 4a to the distribution duct 10 is provided in the upper portion 7a of the positive electrode side electrolyte solution storage tank 7 to achieve the above effect. It helps to do that.

The state of this recovery is shown by the white dots in FIG.

As is clear from FIG. 2, the characteristics similar to the conventional one can be obtained even though the pump 11 operates intermittently.

This is because the first pump 11 is driven to recover most of the bromine complex compound remaining in the electrolytic solution 4a, and the next pump 11
During the rest period, the bromine complex compound mixed in the electrode plate 2 made of felt-like carbon-containing resin is diffused in the electrolytic solution 4a, and the bromine complex compound diffused in the electrolytic solution can be recovered by driving the pump 11 again. Because.

In addition, since the pump is driven intermittently, the bromine complex compound mixed in the felt can be stripped off due to the change in the flow velocity in the initial stage of the driving, and the pump can be effectively recovered.

In addition, although the case where the intermittent operation of the pump is performed every 5 minutes has been described in the above embodiment, the present invention is not particularly limited to this, and can be appropriately set according to the size of the volume of the reaction tank circulation path. .

[Effects of the Invention] As described above, according to the present invention, the bromine complex compound in the electrolytic solution can be recovered in the same manner as in the past by intermittently driving the pump. The efficiency can be improved.

Moreover, since the pump is driven intermittently, the life of the pump can be extended.

[Brief description of drawings]

FIG. 1 is a diagram showing a driving state of a pump according to one embodiment of the present invention, FIG. 2 is a diagram showing characteristics of recovery time and electric capacity in a cleanout method according to the related art and the present invention, and FIG. FIG. 3 is a diagram showing a basic configuration of a bromine battery. 1 ... Reaction tank 2 ... Positive electrode 3 ... Negative electrode 7,8 ... Storage tank 11 ... Pump 12 ... Complex storage section 13 ... Discharge valve

Claims (1)

[Claims] 1. A metal-bromine battery which circulates an electrolytic solution / bromine complex compound through a circulation path between an electrolytic solution storage tank and a reaction tank to perform a predetermined charge / discharge reaction, wherein the positive electrode side storage tank is The storage part of the bromine complex compound is at the bottom, the discharge valve that can control the outflow of the bromine complex compound to the reaction tank side is at the bottom, and the outlet of the positive electrode side electrolyte solution to the reaction tank side is at the top. In each of the metal-bromine battery clean-out method provided, the discharge valve is closed to prevent the outflow of the bromine complex compound, and a pump disposed in the electrolytic solution circulation path is operated for a predetermined time. A metal-bromine battery clean-out method, characterized in that the electrolytic solution is circulated intermittently to circulate the electrolytic solution, and the bromine complex compound remaining in the reaction tank and the circulation path is recovered in the storage tank.