JPH0439874A - Zinc-bromine battery of stationary electrolyte type - Google Patents

Abstract

PURPOSE:To improve electric efficiency by after adding silica to electrolyte poring it, as gelled electrolyte, between positive and negative electrodes, or after appling silica on a nonwoven cloth made of polyethylene providing it therebetween. CONSTITUTION:Silica is added to electrolyte to form gelled electrolyte, which is pored between positive and negative electrodes 1, 2, or after silica is applied on a nonwoven cloth made of polyethilene it is arranged between the electrodes 1, 2. By turning electrolyte into the gelled state through the addition of silica to the electrolyte, the poring process to a part between the electrodes 1, 2 can be facilitated, and dispersion speed generated at the time of charging is decreased through the addition of silica so that concentration increase speed in bromine in the vicinity of the negative electrode 2 can be restrained. It is thus possible to have a battery with excellent electric efficiency without using a separator.

Description

DETAILED DESCRIPTION OF THE INVENTION A. Industrial Application Field The present invention is directed to a static electrolyte type zinc
Regarding bromine batteries.

B0 Summary of the invention The invention of claim (1) uses carbon plastic electrodes as positive and negative electrodes, provides a positive electrode active layer on the surface of the positive electrode, and
An electrolytic solution containing a dendrite inhibitor is filled between the negative electrodes,
In a sealed electrolyte static type zinc-bromine battery, silica is added to the electrolyte and the electrolyte is injected between the positive and negative electrodes as a gel electrolyte, or the electrolyte is coated on a polyethylene nonwoven fabric or the like.

By providing it between the negative electrodes, it is possible to reduce the diffusion rate of bromine and suppress the increase in bromine concentration near the positive electrode, thereby providing a static electrolyte type zinc-bromine battery with high electricity efficiency.

The invention of claim (2) uses carbon plastic electrodes as positive and negative electrodes, and provides a positive electrode active layer on the surface of the positive electrode.
In an electrolyte stationary zinc-bromine battery with a dendrite inhibitor added between the negative electrode, silica is added to the electrolyte to form a gel electrolyte, and silica and carbon black are added to the electrolyte as the positive electrode active layer. A paste-formed electrolyte is applied to the positive electrode, and the positive electrode is placed on the lower side and the negative electrode is placed on the upper side, and no separator is provided between the positive and negative electrodes, which reduces the cost of the active layer and The thickness can be controlled according to the battery capacity.

The invention of claim (3) uses carbon plastic electrodes for the positive and negative electrodes, provides a positive electrode active layer on the surface of the positive electrode, and
An electrolytic solution containing a dendrite inhibitor is filled between the negative electrodes,
In a sealed static electrolyte type zinc-negative electrode, silica is added to the electrolyte to form a gel electrolyte, and
By providing the positive electrode on the lower side and the negative electrode on the upper side, and dispersing hydrogen storage alloy powder near the negative electrode of the gel electrolyte, the charge/discharge cycle characteristics are greatly improved. .

The invention of claim (4) is the invention of claim (3),
The positive electrode active layer is provided by bonding activated carbon fibers to the electrode by thermocompression, or by applying an electrolytic solution prepared by adding carbon black to a gelled electrolytic solution to form a paste.

C1 Prior Art At present, a large capacity zinc-bromine battery has been developed for power storage (Japanese Patent Publication No. 1-31665).

A zinc-bromine battery is a secondary battery that uses bromine as a positive electrode active material and zinc as a negative electrode active material. This battery reaction is shown below.

The electromotive force is 1.8V.

(Positive electrode) 2B, -4':, B, +2B.

(Negative electrode) Za"+2e22゜ (→charging, ←・discharging) This battery uses polyethylene as an electrode material as a binder to provide conductivity, and carbon black and graphite are used in a weight ratio of 6:3:1, respectively. A carbon-plastic electrode mixed with the following is used.Furthermore, a sheet made of activated carbon fibers such as carbon cloth is heat-sealed to the surface of the positive electrode in order to reduce the reaction overvoltage of bromine.

The electrolyte is placed in a tank separate from the battery body, and is circulated from the bottom to the top of the battery body using a pump during charging and discharging. Through this circulation, the bromine generated at the positive electrode reacts with the bromine complexing agent (quaternary amine) added to the electrolyte and becomes an oil-like precipitate, which is returned to a separate tank and retained at the bottom of the tank. It is pumped into the cell and returned. The components of the electrolyte are Z, B, and NH to lower the resistance of the solution.

Salt such as CI is added, and Pb is added to prevent negative electrode zinc dendrites and promote uniform electrodeposition.

Syu, quaternary ammonium salts (dendritic inhibitor),
and a bromine complexing agent. A separator is used between the positive electrode and the negative electrode to prevent bromine generated at the positive electrode from diffusing into the negative electrode and self-discharging with zinc.

Zinc-bromine batteries have been developed as electrolyte circulation type batteries as described above. Considering a large-capacity stationary type for load leveling, etc., this is more advantageous, and the pump loss used for circulation is smaller than that of the entire battery. If the electrolyte tank is placed separately and the electrolyte is circulated, the distance between the poles of the cell body can be reduced, concentration polarization of the electrochemical reaction can be reduced, and a highly efficient battery can be achieved.

Problems to be solved by the D0 invention On the other hand, batteries used as emergency power sources are required to have high reliability and safety. Therefore, when conventional zinc-bromine batteries are used as an emergency power source, rotating parts such as pumps have poor reliability, and the piping required for circulation is also disadvantageous. In addition, the manifold for sharing the electrolyte has the problem of shunt current. This is disadvantageous, for example, when charging is performed constantly, such as in floating charging. When a shunt current occurs, dendrites are generated and a short circuit occurs.

For the above reasons, when considering emergency power sources, static electrolyte batteries are definitely effective.

When a zinc-bromine battery is of a stationary electrolyte type, there are problems with injection of electrolyte into the cell and uneven concentration within the cell. As one solution to this problem, the applicant has proposed a method using a nonwoven fabric impregnated with an electrolyte.

However, in this case, a step of placing a nonwoven fabric impregnated with electrolyte on the electrode is required, which poses problems in workability and is not suitable for mass production. Furthermore, since dendrites grow with almost the same probability as with normal liquids, the problem of dendrite generation remains.

In addition, the positive electrode of a zinc-bromine battery uses a sheet-shaped activated carbon fiber bonded by thermocompression, which has a large surface area and is stable against currents and does not fall off. In this case, the cost of the positive electrode active layer increases.

Furthermore, in the case of a stationary battery, a sealed structure is required for reasons such as reliability and maintainability. In this case, hydrogen gas (H2) may be generated from the negative electrode during charging.

If gas remains in the cell, problems such as a reduction in the effective area of the electrode, generation of dendrites due to current concentration, etc., and liquid leakage due to increased internal pressure occur.

The present invention has been made in view of these problems, and its purpose is to facilitate the filling process of batteries, to keep the bromine generated at the positive electrode near the electrode, and to The object of the present invention is to provide an inexpensive positive electrode active layer and an electrolyte stationary zinc-bromine battery that can store generated hydrogen.

81 Means for solving the problem In order to achieve the above object, carbon plastic electrodes are used for the positive and negative electrodes, a positive electrode active layer is provided on the positive electrode, and the positive and negative electrodes are provided with a positive active layer.
In an electrolyte stationary zinc-bromine battery in which an electrolytic solution containing a dendrite inhibitor or the like is filled between the negative electrodes, silica is added to the electrolytic solution and the gel is injected between the positive and negative electrodes. Alternatively, the electrode may be coated on a polyethylene nonwoven fabric or the like and provided between the positive and negative electrodes.

Alternatively, the positive electrode active layer can be formed by applying an electrolytic solution prepared by adding silica and carbon black to the electrolytic solution to form a paste onto the positive electrode, and providing the positive electrode on the lower side and the negative electrode on the upper side.

Alternatively, the hydrogen storage alloy powder can be dispersed and provided near the negative electrode of the gel electrolyte with the positive electrode on the lower side and the negative electrode on the upper side.

When silica is added to the F6 working electrolyte to turn the electrolyte into a gel, the process of pouring the liquid between the positive and negative electrodes becomes easier. Additionally, the addition of silica reduces the diffusion rate of bromine generated during charging and suppresses an increase in bromine concentration near the negative electrode, so a battery with good electrical efficiency can be obtained without using a separator. Furthermore, since the silica suppresses the sedimentation rate of the generated bromine, it is possible to make the cell vertical.

When a paste made by adding carbon black to a gel electrolyte containing silica is applied to the electrode surface, it acts as a positive electrode active layer in the same way as activated carbon fibers. Since this positive electrode active layer is in the form of a paste, its thickness can be freely controlled.

The hydrogen storage alloy powder can store the hydrogen generated within the cell, and by storing the hydrogen generated within the cell, the charging and discharging cycle characteristics become stable over a long period of time.

G. Example Embodiments of the present invention will be described with reference to the drawings.

First example FIG. 1 shows a sectional view of a horizontal cell according to the first embodiment.

In FIG. 1, 1 is a positive pole, 2 is a negative pole, and 3 is a positive pole.

A frame-shaped polyethylene packing provided between the negative electrodes 1 and 2, 4 a gel electrolytic solution provided within the frame of the packing 3, 5 and 6 a positive FRP holding plate provided outside the negative electrode, Reference numeral 7 denotes a screw for tightening the presser plates 5, 6, which is inserted into a hole 8 formed in the peripheral edge of the presser plates 5, 6.

As the gel electrolyte 4, 3 mol Z a B
An electrolytic solution consisting of t 2 + 2 mol NH4Cl + 1 mat bromine complexing agent + dendrite inhibitor was used, to which 10 wt % of silica was added as a gelling agent. Silica was chosen as the gelling agent because of its bromine resistance. The silica used was Nibseal (trade name) E22OA or G300 manufactured by Nippon Silikani.

Addition of 5 wt% silica does not result in a gel-like state. 10wt
Although it has fluidity even when % is added, it becomes solid if left in a stationary state. Therefore, it takes 19w to make the electrolyte into a gel state.
It is necessary to add t% or more.

The battery used in the characteristic test had a size of 5 cm x 5 cm, and carbon plastic was used for the positive and negative electrodes 1 and 2.

The distance between poles was 2 mm. Therefore, the electrolyte that enters during this period is 5
It is 0cc. In addition, the positive electrode 1 includes a plastic electrode, a positive electrode active layer 10, and a carbon cloth (A
CC-507 or 509, specific surface area 1500-2000
m''/g, date is 100 to 150 g/m2) was used.A separator was not used in the electrolyte.

The order of making is to place the positive electrode 1 and the packing 3 on the holding plate 5, pour the gel electrolyte into the frame of the packing 3, and then place the negative electrode 2 on the holding plate 5.
The holding plate 6 was placed on top of the holding plate 6, and the screws 7 were tightened around the periphery.

The test results of this battery are shown in FIGS. 2 and 3.

Figure 3 shows the charging/discharging voltage characteristics when charging at a charging current of 20 mA/cm2 (500 mA) for 1 hour and discharging to IV/cell at a discharging current of 20 mA/cm2, and the electrical efficiency is approximately 65%. .

The reason why we were able to obtain this much electricity efficiency without using a separator is because the presence of silica reduces the diffusion rate of bromine, which prevents the concentration of bromine from becoming high near zinc, and because silica adsorbs bromine. It is presumed that this is because the bromine generated at the positive electrode remained near the bromine pole. On the other hand, the presence of silica increases electrical resistance, so
Voltage loss is increasing. The initial discharge voltage is 1.7v
This is about 100 mV higher than when silica is not used. However, in view of the use of emergency batteries, this voltage loss can be compensated for by changing the number of battery layers, and this level of loss does not affect the increase in size when the number of layers is increased.

Figure 3 shows the change in electrical efficiency with respect to the number of cycles of repeated charging and discharging cycles until the discharge end voltage becomes 1, OV/cell at a charging current of 20 mA/cm2 after charging for 1 hour at a charging current of 20 mA/cm. The battery shows almost no change in efficiency over 100 cycles.After 100 cycles of charging, the battery was disassembled, but no dendrites were observed.

This confirmed that silica has a dendrite suppressing effect.

Second example FIG. 4 shows a cross section of a vertical cell of the second embodiment.

In this embodiment, the battery configuration shown in FIG. 1 is arranged vertically as shown in FIG. 4. This vertical battery was made by first assembling the cell with one side edge of the picture frame gasket 3 removed, and then pouring a gel-like liquid into it and fitting the removed side edge.

When the characteristics of this battery were examined under the same conditions as the battery of the first example, the electrical efficiency was 50%. It is estimated that this is because the generated bromine precipitated to the bottom, and the upper part of the electrode was not used effectively, resulting in a decrease from 65% in the horizontal type. However, this is a number that can be adequately addressed by improving the active layer, and it is presumed that the presence of silica slows down the precipitation of bromine.

Third embodiment FIG. 5 shows a cross-sectional view of a horizontal cell according to the third embodiment.

In FIG. 5, this embodiment is a low-cost commercial product made of polyethylene with a thickness of 0.6 mm that is used in lead batteries etc. and is used in lead batteries etc. between the positive electrode 1 and the negative electrode 2 of the battery shown in FIG. A separator 11 is provided.

When the characteristics of this battery were examined under exactly the same conditions as the battery of the first example, an electrical efficiency of 75% was obtained, an improvement of 10% from 65% in the first example.

Fourth Embodiment Referring to FIG. 6, a sectional view of a horizontal cell of the fourth embodiment is shown. In FIG. 6, 12 is a gel-like positive electrode active layer made of a silica-carbon black electrolyte.

This positive electrode active layer 12 has 3 m o I Z * B
T! + 20wt silica in the electrolyte of 2mol NH4cI + 1mol bromine complexing agent + dendrite inhibitor
% addition.

Furthermore, 5 wt% of carbon black was added and dispersed using a shaker.
It was coated uniformly to a thickness of about n to form a positive electrode active layer. The same silica as in Example 1 was used. As the carbon black, Ketchen Black (trade name) EC manufactured by Lion Corporation was used.

The electrolytic solution 4 used was the above electrolytic solution to which 10 wt% of silica was added, and no separator was used.

The electrode area, distance between electrodes, etc. are the same as in the first embodiment, and FRP
Place the electrode 1 provided with the electrolyte positive electrode layer on the presser plate 5,
A frame-shaped packing 3 with a thickness of 2 mm is placed on it, and an electrolyte solution 4. Negative electrode 2. It was made by placing the presser plate 6 in this order and lightly tightening it with the screws 7.

The test results of this battery are shown in FIGS. 7 and 8.

Figure 7 shows charging for 1 hour at a charging current of 20 mA/cm2.
This shows the charging/discharging voltage characteristics when discharged to IV/cell at a discharge current of 20 mA/cm2, and there was almost no change in the characteristics from those of the first example shown by the dotted line.

Figure 8 shows the change in electrical quantity efficiency with respect to the number of cycles in which the charging and discharging cycles of OV/cell are repeated after charging for 1 hour at a charging current of 20 mA/cm' and a discharge end voltage of 1 at a charging current of 20 mA/cm'. As in the first embodiment, the efficiency is stable up to about 100 cycles.

It was found that these characteristics provided the positive electrode active layer 11 with sufficient performance.

Fifth example FIG. 9 shows a cross-sectional view of a horizontal cell according to the fifth embodiment.

In FIG. 9, 13 is a hydrogen storage alloy powder sprinkled on the gel electrolyte 4. In FIG.

The hydrogen storage alloy (hereinafter abbreviated as HAA) used was M i
M using s ch metal, 95% N t s,
hCo. This is an alloy sample of yAlo, a. M i
S ch Memole has 20% lanthanum as its main component. Electrolyte 4 is 3moA'Z, B, 2+2moA
The positive electrode active layer 12 is made of a gel-like electrolytic solution consisting of 'NH4Cl+1moA' bromine complexing agent + dendrite inhibitor with 10 wt% of silica added.The positive electrode active layer 12 is made by adding 5 wt% of carbon black to this electrolytic solution 4 and making it into a paste. Coated. The cell has the positive electrode on the bottom and the negative electrode on the top, and no separator is used. Powdered HAA with a size of about 500 μm to 1000 μm was used.

The method of making the electrode is as follows: Electrode 1. After placing the frame-shaped packing 3 and adding the gel electrolyte 4, HAA powder 13 is sprinkled on the electrolyte 4, and the negative electrode 2. It was made by mounting a presser plate 5 and fixing it with screws 7.

The test results for this battery are shown in FIG.

Figure 10 shows that after charging for 1 hour at a charging current of 20 mA/cm2, the discharge end voltage was 1.OV at a discharging current of 20 mA/cm2.
This shows the change in electrical efficiency with respect to the number of repeated charge and discharge cycles until a cell is formed.If HAA is not added, the efficiency decreases after about 100 to 150 cycles and eventually an internal short circuit occurs, but HAA When adding 3
It showed stable characteristics up to about 00 cycles. It is thought that the hydrogen generated internally is stored by HAA.

Figure 11 shows the hydrogen generation amount detection device for the battery.
0 uses a liquid electrolyte that does not gel so that gas can escape well, and the separator 21 is used to make the electrolyte positive.

This shows a battery in which the negative electrode is separated and HAA powder is added to the negative electrode liquid, or a battery in which HAA powder is not added. 22 is a sealed glass container containing the battery, 23 is a glass tube for extracting gas, 24 is a container containing water, 25 is a measuring cylinder for measuring the amount of gas coming out of the glass tube, and E is a DC power source for charging the battery 20. be.

FIG. 12 shows changes in the amount of repair gas measured by this measuring device. According to FIG. 12, when HAA is added to the negative electrode liquid, there is almost no increase in gas volume. This results in H
It is assumed that AA stores H2 generated within the cell.

H1 Effects of the invention Since the zinc-bromine battery of the invention is configured as described above, it exhibits the following effects.

■By adding silica to the electrolyte, the electrolyte is made into a paste, which facilitates the injection process between the cell electrodes.

■The addition of silica also reduces the diffusion rate of bromine,
Since the increase in bromine concentration near the negative electrode is suppressed, electrical efficiency of 65% or more is possible without using a separator.

In addition, silica not only suppresses the diffusion rate of bromine, but also
Since it has the effect of adsorbing bromine, bromine generated at the positive electrode can be retained near the positive electrode.

■ Adding silica is also effective in suppressing dendrites.

(2) In the invention of claim (1), since the sedimentation rate of bromine generated by silica is suppressed, it is also possible to make the cell vertical.

■In the invention of claim (2), by applying a paste made by adding carbon black to a gel electrolyte containing silica as a positive electrode active layer, it has properties equivalent to conventional activated carbon fibers. was gotten. This makes it possible to reduce the cost of the positive electrode active layer.

■Also, the thickness of the positive electrode active layer can be controlled according to the battery capacity.

(2) In addition, the positive electrode active layer does not move, and since the positive electrode is oriented downwardly and upwardly, it does not fall off, so that sufficient cycle characteristics can be obtained.

(2) In the inventions of claims (3) and (4), hydrogen generated within the cell can be stored in the hydrogen storage alloy added to the electrolyte. This greatly improves charge-discharge cycle characteristics. In addition, leakage of liquid to the outside due to an increase in internal pressure due to generated gas can be prevented.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a horizontal cell showing the first embodiment, FIG. 2 is a charging/discharging voltage characteristic curve diagram of the same cell, and FIG. 3 is a charging/discharging cycle characteristic curve diagram of the same cell. FIG. 4 is a sectional view of a vertical cell showing the second embodiment, FIGS. 5 and 6 are sectional views of a horizontal cell showing the third and fourth embodiments, and FIG. 7 is a sectional view of a cell of the fourth embodiment. Fig. 8 is a charge/discharge cycle characteristic curve of the same cell, Fig. 9 is a cross-sectional view of a horizontal cell showing the fifth embodiment, and Fig. 10 is a charge/discharge cycle characteristic of the same cell. FIG. 11 is a curve diagram showing an apparatus for detecting the amount of hydrogen generated in a battery, and FIG. 12 is a curve diagram showing the amount of gas repaired in a battery by the same apparatus. 1... Positive electrode, 2... Negative electrode, 3... Packing, 4...
... Electrolyte holder, 5, 6... Pressing plate, 10.12.
... Positive electrode active layer, 11.21 ... Separator, 13.
...Hydrogen storage alloy (HAA). Fig. 1 Fig. 1 Example Fig. 4 Fig. 2 Example Time (minutes) Fig. 5 Fig. 3 Example Fig. 6 Fig. 4 Example Fig. 9 Fig. 5 Example Number of charge/discharge cycles Fig. 8 Number of charge/discharge cycles Figure 12 (B)

Claims (4)

[Claims] (1) Use carbon plastic electrodes for positive and negative electrodes,
In electrolyte stationary zinc-bromine batteries, a positive electrode active layer is provided on the surface of the positive electrode, and an electrolytic solution containing a dendrite inhibitor is filled between the positive and negative electrodes and sealed. 1. A static electrolyte type zinc-bromine battery, characterized in that the electrolyte is injected between the positive and negative electrodes or coated on a polyethylene nonwoven fabric and provided between the positive and negative electrodes. (2) Using carbon plastic electrodes for positive and negative electrodes,
In a static zinc-bromine battery, a positive electrode active layer is provided on the surface of the positive electrode, and a dendrite inhibitor is added between the positive and negative electrodes. An electrolytic solution made by adding silica and carbon black to the electrolytic solution to form a paste is applied to the positive electrode as a layer, and the positive electrode is placed on the lower side and the negative electrode is placed on the upper side.
An electrolyte stationary zinc-bromine battery characterized by not having a separator between the negative electrodes. (3) Using carbon plastic electrodes for positive and negative electrodes,
In an electrolyte stationary zinc-negative electrode, a positive electrode active layer is provided on the surface of the positive electrode, and an electrolytic solution containing a dendrite inhibitor is filled between the positive and negative electrodes and sealed, silica is added to the electrolytic solution. A stationary electrolyte type zinc electrolyte, characterized in that the electrolyte is a gel electrolyte, a positive electrode is provided on the lower side, a negative electrode is provided on the upper side, and hydrogen storage alloy powder is dispersed in the vicinity of the negative electrode of the gel electrolyte. - Bromine batteries. (4) Claim characterized in that the positive electrode active layer is provided by bonding activated carbon fibers to the electrode by thermocompression, or by applying an electrolytic solution made by adding carbon black to a gelled electrolytic solution to form a paste ( 3) The static electrolyte zinc-bromine battery.