JPH02135671A - Metal-halogen battery - Google Patents

Abstract

PURPOSE:To efficiently continue reaction even at the time of complete discharge by installing a halogen supply tank in a positive electrode side electrolyte storage tank, and installing a diffusion membrane in the halogen supply tank to permeate only halogen vapor and to keep halogen concentration in an electrolyte in a specified value. CONSTITUTION:When a battery is charged, zinc 200 is deposited on a negative electrode 12a in a negative chamber 16, and a bromine complex is formed in a positive chamber 18 and stored in a bromine complex storage tank 28. When the battery is discharged, zinc 200 is ionized to Zn<2+> on the negative electrode side and bromine of the bromine complex 100 is converted into 2Br<->. Bromine is replenished from a halogen supply tank 36 before bromine concentration is decreased to keep bromine concentration in an electrolyte in a range of 0.05-0.1mol. Even in complete discharge, discharge reaction is surely continued. Zinc is smoothly dissolved on the negative electrode side and generation of dendrite is prevented. A diffusion membrane 38 such as 'Teflon(R)' film permeates only halogen without permeation of the electrolyte.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a metal-halogen battery, and in particular to the structure of an electrolyte storage tank for efficiently carrying out charging and discharging reactions by circulating an electrolyte in a reaction tank. be.

[Prior Art] A metal-halogen battery with an electrolyte circulation type is used as a secondary battery with a large stored energy as a power source for an electric vehicle.
It is shown in detail in 9167 publication and the like.

FIG. 3 shows an outline of such a conventional metal-halogen battery, in which a reaction tank 10 is provided with a negative electrode 12a and a positive electrode 12b, and a separator 14 is provided between these two electrodes. The negative electrode chamber 16 and the positive electrode chamber 18 are formed separately.

The negative electrode liquid is circulated into the negative electrode chamber 16 from the negative electrode liquid storage tank 20 by a pump 24, and the positive electrode liquid is circulated into the positive electrode chamber 18 from the positive electrode liquid storage tank 22 by a pump 26. Further, a bromine complex compound storage tank 28 is provided in the positive electrode liquid storage tank 22, and this bromine complex compound is stored in the valve 3.
o is mixed into the positive electrode electrolyte at the required time.

As such a metal-halogen battery, for example, zinc (Z
n)-bromine (B'') is used, and a quaternary ammonium salt complexing agent such as methyl, ethyl, and sophorinium bromite is added to the positive electrode electrolyte, and this complexing agent reacts with bromine. It plays the role of forming a bromine complex compound that is insoluble in the electrolyte and has a higher specific gravity than the electrolyte.Also, in order to increase the conductivity of the electrolyte, for example, KC
, e, NH4Cj! It is also possible to add a supporting electrolyte such as .

According to such a configuration, during charging, the negative electrode 12a in the figure
Zn is produced at the positive electrode 12b, and Br2 is produced at the positive electrode 12b, and the following reaction takes place.

Positive electrode 2Br--e Br2+2e=(1) Negative electrode Z
n”+2e4 Zn −(2) and positive electrode 1
The bromine produced in step 2b reacts with the complexing agent to form a bromine complex, and this bromine complex is supplied from the reaction tank 10 to the bromine complex storage tank 28 and precipitated as shown in the figure 100. . On the other hand, the zinc generated at the negative electrode 12a is electrolytically deposited (electrodeposited) on the electrode plate of the negative electrode 12a.

Therefore, during discharge, a reaction opposite to the reaction formula described above takes place at each electrode, and a predetermined current is thereby extracted from between the electrodes.

In such an electrolyte circulation type battery, 0.05 to 0.1 M (0.05 to 0.1 M) of bromine is added to the positive electrode solution in advance so that all the zinc deposited on the negative electrode 12a is well dissolved during complete discharge.
It is added in an amount of about mol/J, thereby maintaining good charge/discharge efficiency.

[Problems to be Solved by the Invention] However, conventional metal-bromine batteries have a problem in that the bromine concentration gradually decreases due to the following reason.

b) The components that make up the battery absorb bromine.

), bromine permeates the battery container and gradually diffuses to the outside.

c) Bromine reacts directly with water in the electrolyte to generate unnecessary bromine compounds in the positive electrode solution, which is expressed in the following reaction formula.

Hz O+B r2-HB ro+HB r-(3)H
B ro →HB r+ (1/2)02− (4) In this equation, HBr0 is decomposed according to equation (4), but it is not completely decomposed and remains little by little in a state containing bromine.

The decrease in bromine concentration caused by the above-mentioned reason becomes a reaction resistance in charge/discharge reactions, resulting in a problem of lowering current efficiency and energy efficiency. In addition, during complete discharge, zinc is not completely dissolved on the negative electrode side due to lack of bromine, so repeated charging and discharging gradually deteriorates the state of zinc electrodeposition and forms dendrites, which can damage the separator 14, This can also cause a short circuit within the battery.

In order to avoid such problems, it is necessary not only to add bromine once in advance as mentioned above, but also to add bromine regularly once or twice a month. maintenance becomes complicated.

Further, since it is not easy to determine whether the bromine concentration in the electrolyte is below a specified amount, it is also difficult to accurately determine when to add bromine during maintenance.

For this reason, a large amount of bromine (0.5M or more) is sometimes added in advance, but in this case, the amount of complexing agent to complex the added bromine must also be increased. As a result, the weight of the battery increases, which is undesirable.

For example, when 0.5 M of bromine is added, the battery weight increases by 4-6% compared to conventional batteries.

Furthermore, when large amounts of bromine and complexing agents are added, the viscosity and specific gravity of the electrolyte increase, which increases the pump output for circulating the electrolyte, which results in a decrease in the energy density of the battery when considered in total.

The above-mentioned problems also occur in other metal-halogen batteries, and there is a need to effectively prevent the reduction of halogen substances.

In addition, in conventional batteries, in order to control the chlorine concentration in the electrolyte to a constant level in zinc-chlorine batteries, Japanese Patent Laid-Open No. 60
There is one shown in Japanese Patent No.-208068.

OBJECTS OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems, and its purpose is to effectively avoid a decrease in the concentration of halogen substances without complicating maintenance, and to improve charge/discharge reactions. The object of the present invention is to provide a metal-halogen battery that can be operated efficiently.

[Means for Solving the Problems] In order to achieve the above object, a metal-halogen battery according to the present invention includes a halogen substance replenishment tank and a diffusion membrane, and the halogen substance replenishment tank stores a halogen substance. and is provided in the positive electrode side electrolyte storage tank. Further, the diffusion membrane is provided in the halogen substance replenishment tank, and allows the vapor of the halogen substance to pass through while not allowing the electrolyte to pass through, thereby maintaining the halogen substance concentration in the electrolyte at a predetermined value. It is characterized by consisting of a microporous membrane.

[Function] According to the above configuration, the vapor of the halogen substance, such as bromine, stored in the halogen substance replenishment tank permeates through the diffusion membrane and dissolves into the electrolyte on the positive electrode side.

In this case, the amount of dissolved bromine is adjusted to a predetermined value by the diffusion membrane, and as a result, the bromine concentration in the electrolyte during discharge is always maintained constant, so an efficient reaction state can be maintained even during complete discharge. Secured.

[Examples] Hereinafter, preferred embodiments of the present invention will be described based on the drawings.

FIG. 1 shows a schematic configuration of a zinc-bromine battery according to an example, and the basic configuration is the same as that shown in FIG. 3 described above.

That is, the reaction tank 10 in which the negative electrode 12a and the positive electrode 12b are provided includes a negative electrode liquid storage tank 20 which is an electrolyte storage tank.
The electrolytic solution is configured to be circulated from the positive electrode liquid storage tank 22, and the positive electrode liquid storage tank 22 is provided with a bromine complex compound storage tank 28 for storing a bromine complex compound.

A feature of the present invention is that the bromine concentration can always be maintained constant, and for this purpose, a halogen substance replenishment tank 36 storing bromine 34 (liquid) is provided in the positive electrode liquid storage tank 22. . A diffusion film 38 is formed on the upper surface of this halogen substance replenishment tank 36 to diffuse the stored bromine vapor.

This diffusion membrane 38 is made of Teflon, polyethylene, or the like, and is formed so that it does not allow the electrolyte to pass through, but allows only the halogen substance (in the example, bromine) to pass therethrough. (The separator 1
Microporous membranes such as those similar to 4) can be used. The film thickness, area, etc. of this diffusion film 38 are determined in consideration of the diffusion rate of bromine, and in the embodiment,
The bromine concentration in the positive electrode electrolyte during complete discharge is always 0.05~
The diffusion film 38 is provided with a thickness and area of 0.1 M (mole).

In addition, in the embodiment, as shown in FIG. 2, in order to check the remaining amount of bromine 34 in the halogen substance replenishment tank 36, the case of the positive electrode liquid storage tank 22 equipped with the halogen substance replenishment tank 36 is Confirmation window 4 made of transparent material in a predetermined area
0 is set. According to this confirmation window 40, the remaining amount of bromine 34 can be easily confirmed at a glance.

The embodiment has the above configuration, and its operation will be explained below.

First, during charging, the negative electrode chamber 1
6, zinc 200 is deposited on the negative electrode 12a, and in the positive electrode chamber 18, a bromine complex compound is formed according to equation (2), and this bromine complex compound is accumulated in the bromine complex compound storage tank 28.

On the other hand, during discharging, the reverse reaction of equations (1) and (2) takes place, and on the negative electrode side, zinc 200 is ionized and Z
n2+, and on the positive electrode side, bromine of the bromine complex compound 100 is ionized to become 2Br-.

At this time, conventionally, as the charge/discharge cycle progresses, the bromine concentration in the positive electrode liquid storage tank 22 decreases due to the causes shown in a), ex), and c) on page 4, and especially in the case of complete discharge, the bromine concentration decreases due to the lack of bromine. A situation occurs where the zinc on the negative electrode side is not completely dissolved.

However, in the present invention, bromine is replenished from the halogen substance replenishment tank 36 before the bromine concentration decreases, so the bromine concentration in the electrolyte can be maintained at 0.05 to 0.1 mol, and the bromine concentration is completely discharged. A good discharge reaction will be carried out even at times. Therefore, zinc is well dissolved on the negative electrode side, and the generation of dendrites can be prevented.

Furthermore, in the embodiment, if bromine is stored in the halogen substance replenishment tank 36 in an amount equivalent to 0.5M based on the total amount of electrolyte, it is possible to operate the battery for approximately one year without replenishing bromine. It is.

Further, the remaining amount of bromine in the halogen substance replenishment tank 36 can be checked through the confirmation window 40, making it possible to replenish the halogen substance according to the state of consumption, which has the advantage of facilitating maintenance. .

[Effects of the Invention] As explained above, according to the present invention, a halogen substance replenishment tank is provided in the positive electrode side electrolyte storage tank, and the halogen substance vapor is not allowed to pass through the halogen substance replenishment tank. By providing a diffusion membrane that allows the electrolyte to pass through and maintain the concentration of halogen substances in the electrolyte at a predetermined value, it is possible to compensate for the halogen substances that decrease as the discharge progresses, making it possible to carry out charging and discharging reactions efficiently. becomes.

Further, by storing the halogen substance in the replenishment tank, the halogen substance can be supplied for a long period of time, and maintenance becomes extremely easy.

Furthermore, the present invention does not require the addition of a complexing agent (only bromine can be supplied, so the weight of the battery does not increase, and the viscosity and specific gravity of the electrolytic solution increase, causing energy loss due to increased pump load). The advantage is that there is no problem.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing the schematic structure of the metal-halogen battery according to the present invention, FIG. 2 is a diagram showing a confirmation window for checking the remaining amount of halogen material in the halogen material replenishment tank, and FIG. A theory showing the outline of a metal-bromine battery Reaction tank... Negative electrode... Positive electrode, negative electrode liquid storage tank, positive electrode liquid storage tank, bromine complex compound storage tank, bromine halogen substance replenishment tank, diffusion membrane confirmation window 4 times. 10 ... 2a 2b 20 ... 22 ... 28 ... 34 ... 36 ... 38 ... 40 ... Figure 1 38: Received Diffusion II

Claims (1)

[Claims] (1) In a metal-halogen battery in which charging and discharging reactions occur by circulating electrolyte from an electrolyte storage tank to a reaction tank, a halogen substance replenishment tank is installed in the positive electrode side electrolyte storage tank and stores halogen substances; 1. A metal-halogen battery, comprising: a diffusion membrane provided in a halogen substance replenishment tank, which allows vapor of the halogen substance to pass therethrough without allowing the electrolyte to pass therethrough, and maintains the concentration of the halogen substance in the electrolyte at a predetermined value.