JPH08279367A - Sealed zinc-bromine battery - Google Patents

Abstract

PURPOSE: To attain miniaturization, weight reduction and cost reduction in short time capacity by sandwiching layered bodies composed of a conductive bromine adsorbing body which can be impregnated with electrolyte, an insulator which can be impregnated with the electrolyte and a conductive porous film sandwiched by insulating net bodies, by electrode plates. CONSTITUTION: Layered bodies composed of an electrode plate 1p, a conductive bromine adsorbing body 2, an insulator 3, net bodies 4 and 6 and a porous film 5 are layered in a plurality, and an electrode plate in is layered on the tail end, and is fastened by a bolt or the like, and a multilayer battery is formed. After electrolyte is impregnated and injected, it is also sealed by a plastic frame 11 and a plastic frame 8 to which the electrode plates 1p and in are adhered. For example, carbon plastic is used as the electrode plates 1p and in, and carbon fiber which has the surface area not less than a specific value and is activated in a fiber shape is used as the adsorbing body 2. Glass wool is used as the insulator 3, and net-like plastic is used as the net bodies 4 and 6, and carbon-applied paper is used as the film 5. When charging, bromine is adsorbed to the adsorbing body, and growth of dendrite-shaped zinc is once stopped by the film 5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sealed zinc-bromine battery.

[0002]

2. Description of the Related Art A zinc-bromine battery is a simple and high energy density battery composed of an aqueous solution of zinc bromide and a pair of electrodes. Conventionally, it is considered to be used as a relatively large-scale secondary battery. Has been done. The basic electrochemical reaction is shown in Chemical Formula 1 below.

[0003]

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As shown in the above formula, during charging, the negative electrode is made of zinc Z.
n is deposited, and bromine Br ₂ is produced on the positive electrode. Bromine Br ₂ generated in the positive electrode is dissolved in the electrolytic solution and gradually diffuses. At the time of discharge, zinc Zn deposited on the negative electrode is oxidized to become zinc ions Zn ²⁺ and dissolved in the electrolytic solution, and bromine Br ₂ in the electrolytic solution is reduced to bromine ions 2Br ⁻ similarly in the electrolytic solution. Dissolve. As described above, in the zinc-bromine battery, the active material is dissolved in the electrolytic solution, so that the battery capacity is determined by the capacity of the electrolytic solution.
A bromine battery is a relatively large-scale battery that has an electrolytic solution circulation structure in which an electrolytic solution storage tank is separately provided in addition to the battery reaction tank to increase the electrolytic solution capacity and the electrolytic solution is circulated to the battery reaction tank. Development is proceeding as a secondary battery.

The outline of the electrolyte circulating zinc-bromine battery is as follows. As described above, during charging, the bromine Br ₂ generated in the positive electrode is dissolved and diffused in the electrolytic solution, so that it re-reacts with zinc Zn deposited on the negative electrode to cause self-discharge. The electrolytic solution and the electrolytic solution on the positive electrode side are separated by a separator membrane such as an ion exchange membrane or a porous membrane that allows bromine ions Br ⁻ and zinc ions Zn ²⁺ to permeate but blocks bromine Br ₂ and zinc Zn permeates. Has been done.

In addition, zinc-bromine batteries also contain bromine B
In order to prevent the diffusion of r _2, a complexing agent is added to the electrolytic solution on the positive electrode side to separate and precipitate the produced bromine Br ₂ as a complex compound that is difficult to dissolve in the electrolytic solution, or to deposit on the negative electrode. Zinc Zn is less likely to be smooth due to uneven electric field distribution in the vicinity of the negative electrode surface, and is likely to cause so-called dendrite-like deposition of dendrites, which gradually grows and breaks through the separator film to cause a short circuit with the positive electrode. The zinc dendrite inhibitor and the like are added so as not to cause the destruction of the metal, and the conductivity improver is added as necessary. Electrodes need to have high electrical conductivity and high reactivity with the active material, and since bromine resistance is required for the positive electrode in particular, carbon plastic (CP) or porous with activated surface is used. Quality carbon-based composite materials are used. The basic structure of the zinc-bromine battery is shown in FIG. In the figure, 1 is a battery reaction tank, 2 is a positive electrode chamber, 3 is a negative electrode chamber, 4
Is a separator film, 5 is a positive electrode, 6 is a negative electrode, 7 is a positive electrode electrolyte solution, 8 is a negative electrode electrolyte solution, 9 and 10 are positive electrode electrolyte solution storage tanks and negative electrode electrolyte solution storage tanks, 11 and 12 are pumps, and 13 is a valve. , 71 are complex compounds.

As described above, since the zinc-bromine battery has a simple structure and the battery capacity is determined by the electrolytic solution capacity, it is used as a comparatively large-scale secondary battery of the electrolytic solution circulation type, for example, surplus power at night. It is well known that many developments have been made since ancient times as one of large-scale batteries such as a battery for electric power storage for effective use of (for example,
The Institute of Electrical Engineers of Japan Vol. 103, No. 8, August 1983, Tokuhei 5-
82034, Japanese Patent Publication No. 5-82713).

However, such a zinc-bromine battery having a high energy density is sealed and, for example, UPS is used.
(Uninterruptible Power Supply) and other applications that require a large discharge current but require a small rated capacity for a short time, have not been developed for application as a small, lightweight, inexpensive secondary battery. Therefore, if the zinc-bromine battery having the structure that has been conventionally developed is to be directly applied to a secondary battery for the purpose of small size and light weight, there are the following problems. That is, a zinc-bromine battery has an electromotive voltage of about 1.8 V per cell, and it is necessary to stack a number of cells or connect them in series to obtain a practical voltage. To configure this with a bromine battery, it is desirable to have a negative electrode electrolyte storage tank, a positive electrode electrolyte storage tank, each pump, etc. for each cell, and these are insulated between each cell, and the positive electrode and the negative electrode. Only need be connected. It is also necessary to balance the operation of each pump. Since the structure is very complicated and complicated in this way, it is obvious that it is difficult to realize a zinc-bromine battery on a small scale without a merit of scale. Further, even when the negative electrode electrolyte storage tank, the positive electrode electrolyte storage tank and the like are configured in common for each cell, a circulating current based on the potential difference between the cells in the electrolytic solution causes a loss, It is difficult to apply as a small-scale secondary battery.
Therefore, in applying the zinc-bromine battery as a small, lightweight, and inexpensive secondary battery that is used for a relatively large current for a short time with a small rated capacity, it is desirable to configure it as a laminated battery with a sealed structure. Be done.

[0009]

However, in constructing a laminated zinc-bromine battery having a sealed structure, there are the following problems to be solved. That is, zinc-
As described above, in a bromine battery, the active material is dissolved in the electrolytic solution, and the capacity is determined by the amount of the electrolytic solution. Although it is very effective in constructing a battery, conversely, when it is constructed in a sealed type, the amount of active material in the sealed electrolytic solution is different from that of a lead storage battery or other active material in the electrode plate. Since the amount is smaller than that of the formed battery, it is extremely small as compared with those batteries. Therefore, if the width in the thickness direction of the reaction tank of the battery is increased and it is attempted to seal the electrolyte solution of a considerable capacity, it is difficult to make the battery compact and lightweight, and the internal resistance increases. However, in order to reduce the internal resistance by increasing the width in the surface direction to form a thinner laminated structure, the diffusion of bromine Br ₂ generated in the positive electrode into the electrolytic solution and the negative electrode There is a problem that the self-discharge becomes intense due to the dendrite-like zinc that precipitates on the surface. The present invention was made to study such problems, and was able to obtain a small-sized, lightweight, short-time capacity and inexpensive sealed zinc-bromine battery that can be practically used for UPS and the like.

[0010]

According to a first aspect of the present invention, a conductive bromine adsorbent which can be impregnated with an electrolytic solution, an insulator which faces the bromine adsorbent and can be impregnated with an electrolytic solution, and this insulator And a conductive porous film sandwiched between insulating nets facing each other and sandwiched by an electrode plate for sealing. A second aspect of the present invention is characterized in that, in the first aspect of the present invention, the bromine adsorbent is fibrous activated carbon.

[0011]

[Function] The conductive bromine adsorbent that can be impregnated with the electrolytic solution is in contact with the electrode plate to increase the electrode surface area to activate the electrochemical reaction, and to impregnate the electrolytic solution to increase the battery capacity, and Bromine Br ₂ generated during charging is adsorbed to reduce dissolution of bromine Br _{2 in} the electrolytic solution and suppress self-discharge due to the dissolution. The insulator that can be impregnated with the electrolytic solution becomes an insulator on the positive electrode side and the negative electrode side in the laminated fastening, and impregnates a considerable capacity of the electrolytic solution to have a desired battery capacity. The conductive porous film sandwiched by the insulating netting inhibits the growth of dendrite-like zinc deposited during charging on the surface of the porous film, and suppresses self-discharge due to the growth. Based on these synergistic effects, it becomes possible to obtain a practical compact, lightweight, short-time capacity sealed zinc-bromine battery.

[0012]

EXAMPLE FIG. 1 shows an example of the basic structure of the sealed zinc-bromine battery of the present invention. In the figure (a), 1p, 1
b, 1n are electrode plates, 2 is a conductive bromine adsorbent that can be impregnated with an electrolytic solution, 3 is an insulator that can be impregnated with an electrolytic solution, 4 and 6
Is an insulating mesh and 5 is a conductive porous film. As shown in the figure (from left side in the figure), the electrode plate 1
p, a bromine adsorbent 2, an insulator 3, a net 4, a porous film 5, and a net 6 are laminated, and if necessary, the electrode plate 1b and the bromine adsorbent 2 are further combined. As described above, a plurality of layers are laminated, the electrode plate 1n is laminated at the final end, and the electrode plates 1n are collectively tightened with bolts or the like to be integrated to form one laminated battery.

FIG. 1 (b) shows a one-layer structure of the embodiment in which the above structure is hermetically formed by the electrode plates 1p and 1n to which the plastic frame 11 is attached and the plastic frame 8. As shown in the figure, a plastic frame 11 is attached to the outer periphery of the electrode plates 1p and 1n.
Between p and 1n, the bromine adsorbent 2, the insulator 3, the net 4,
The porous membrane 5 and the net body 6 are laminated, and a plastic frame 8 having a thickness corresponding to the tightening thickness of this lamination is inserted into the above-mentioned plastic frame 11 and attached to the electrode plates 1p and 1n. The portion of the frame 11 is bolted. The plastic frame 11 is attached to the electrode plates 1p and 1n by adhesion, the plastic frame 8 is adhered to the plastic frame 11 of the electrode plate 1p, and the inner layer is sealed with a sealant between the electrode plate 1n and the inside. The electrolyte solution (ZnBr ₂ aqueous solution) impregnated and injected into is sealed. In this configuration, the electrode plate 1p to which the bromine adsorbent 2 is in close contact serves as the positive electrode,
The electrode plate 1n forms a negative electrode. The electrode plate 1b, which serves as an intermediate electrode plate in the multilayer stacking, forms a bipolar electrode in which the side facing the mesh 6 is the negative electrode and the side in close contact with the bromine adsorbent 2 is the positive electrode.

The electrode plates 1p, 1b, and 1n are required to have high conductivity and have no fear of being corroded by bromine, and carbon plastic (CP) which has been mainly used conventionally is used for this. The configuration according to the present invention is the electrode plate 1
bromine adsorber ₂ which has a high conductivity and is capable of adsorbing a large amount of bromine Br ₂ by impregnating it with an electrolytic solution facing p. The purpose is to use the insulator 3 that can be impregnated with the liquid and the conductive porous film 5 sandwiched between the nets 4 and 6. In the embodiment, the bromine adsorbent 2 is about 1 per 1 g.
Fiber activated carbon fiber (ACF) having a surface area of 000 m ² or more, for example, activated carbon fiber krative manufactured by Kuraray Chemical Co., is used to form glass wool as the insulator 3 and reticulated as the insulating nets 4 and 6 Made of plastic. The porous film 5 was prepared by dissolving and mixing carbon powder in an adhesive (solvent), applying it to filter paper (Whatman No. 42), and drying it. The porous film 5 is preferably a film that is electrically conductive and allows only ions to pass through, but good results have also been obtained with the above-mentioned carbon-coated paper used in place of this. Further, not only the electrolyte 3 is impregnated with the electrolytic solution but also the bromine adsorbent 2 is impregnated to fill the voids in the stack.

In this structure, when the electrode plate 1p is charged with the positive electrode and the electrode plate 1n is charged with the negative electrode, as described above, the side of the positive electrode side electrode plate 1p and the side of the electrode plate 1b where the bromine adsorbent 2 is in contact with is bromine Br. ₂ is generated, and zinc Zn is deposited on the side of the negative electrode side of the electrode plate 1n and the electrode plate 1b that faces the net body 6. At this time, on the positive electrode side, since the bromine adsorbent 2 is in close contact, the generated bromine Br ₂ is immediately adsorbed on the bromine adsorbent 2 and is less dissolved in the electrolytic solution, so that the diffusion to the negative electrode side is extremely suppressed. As a result, self-discharge due to this is greatly reduced. On the negative electrode side, zinc Zn deposited in a dendrite shape has a uniform electric field at the tip when the tip thereof contacts the porous film 5, and the electric field at the tip is uniformly relaxed. Will once stop at the surface of the porous film 5.

When the charging is further advanced, the porous film 5 becomes the negative electrode, and the dendrite-like zinc is deposited on the side of the porous film 5 facing the positive electrode side. However, the sealed zinc-bromine battery of the present invention is used. Since the capacity up to that time is not obtained, an internal short circuit is generated by the dendrite-like precipitated zinc by using the net body 6 having an optimum thickness corresponding to the amount of the electrolytic solution impregnated and injected inside. Nor does it promote self-discharge. During discharge, bromine Br ₂ adsorbed on the bromine adsorbent 2 on the positive electrode side becomes bromine ions Br ⁻ , and zinc Zn deposited on the negative electrode side becomes zinc ions Zn ²⁺ and dissolves in the electrolytic solution. Further, not only the amount of the electrolytic solution and the thickness of the net body 6 described above are selected, but also the thickness of the bromine adsorbent 2, the insulator 3, the net body 4 and the compression pressure of the stack are optimally adjusted to reduce the internal resistance. It is possible to construct a sealed zinc-bromine battery which has a desired small size, light weight, and short time capacity.

[0017]

EFFECTS OF THE INVENTION With such a structure, diffusion of bromine Br ₂ is suppressed, and dendrite-like zinc deposition on the negative electrode is also suppressed. Therefore, self-discharge is small, internal resistance is low, and a large discharge current can be obtained. In addition, it is possible to obtain a practical small-sized, lightweight, short-time capacity, inexpensive, sealed zinc-bromine battery that can be sealed with a considerable amount of electrolytic solution. In addition, stacking is easy and a device having a required voltage can be easily obtained.

[Brief description of drawings]

FIG. 1 is a diagram showing an example of the configuration of a sealed zinc-bromine battery of the present invention.

FIG. 2 is a diagram showing a basic configuration of a conventional sealed zinc-bromine battery.

[Explanation of symbols]

 1p, 1b, 1n Electrode plate 2 Bromine adsorbent 3 Insulator 4, 6 Net 5 Porous membrane

Claims (2)

[Claims] 1. A conductive bromine adsorbent which can be impregnated with an electrolytic solution, an insulator which is arranged facing the bromine adsorbent and which can be impregnated with an electrolytic solution, and an insulating mesh which is arranged facing this insulator. A sealed zinc-bromine battery, characterized in that a laminated body composed of a conductive porous membrane sandwiched between the body is sandwiched between electrode plates and sealed. 2. The sealed zinc-bromine battery according to claim 1, wherein the bromine adsorbent is fibrous activated carbon.