JP2853273B2 - Electrolyte static zinc-bromine battery - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION A. Industrial Field of the Invention The present invention relates to an electrolyte stationary type zinc-bromine battery in which an electrolyte is not circulated.

B. Summary of the Invention The invention of claim (1) uses a carbon plastic electrode for positive and negative electrodes, and provides a positive electrode active layer on the positive electrode surface,
In a static electrolyte zinc-bromine battery, which is filled with an electrolyte containing a dendrite inhibitor between the positive and negative electrodes and sealed, silica is added to the electrolyte to form a gel electrolyte between the positive and negative electrodes. Injection or coating on polyethylene non-woven fabric, etc., between the positive and negative electrodes reduces the bromine diffusion rate and suppresses the concentration and increase of bromine in the vicinity of the positive electrode. -A bromine battery is obtained.

The invention of claim (2) uses a carbon plastic electrode for the positive and negative electrodes, provides a positive electrode active layer on the positive electrode surface,
In a static electrolyte zinc-bromine battery in which a dendrite inhibitor is added between a positive electrode and a 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. Is applied to the positive electrode, and the negative electrode is provided on the upper side with the positive electrode on the lower side, and no separator is provided between the positive and negative electrodes, thereby reducing the cost of the active layer. In addition, the thickness can be controlled according to the battery capacity.

According to the invention of claim (3), a carbon plastic electrode is used for the positive and negative electrodes, a positive electrode active layer is provided on the positive electrode surface,
An electrolyte solution containing a dendrite inhibitor added between a positive electrode and a negative electrode is filled in a sealed electrolyte-static zinc-negative electrode, and silica is added to the electrolyte to form a gel electrolyte, and the positive electrode is formed. The negative electrode is provided on the upper side on the lower side, and the hydrogen storage alloy powder is dispersed and provided in the vicinity of the negative electrode of the gel electrolyte so that the charge / discharge cycle characteristics are greatly improved.

According to the invention of claim (4), in the invention of claim (3), the positive electrode active layer is formed by thermocompression bonding an activated carbon fiber to an electrode, or by adding carbon black to a gelled electrolytic solution and forming a paste. It is provided by applying a liquid.

C. Prior Art At present, large capacity zinc-bromine batteries have been developed for power storage (Japanese Patent Publication No. 1-36565).

A zinc-bromine battery is a secondary battery using bromine as a positive electrode active material and zinc as a negative electrode active material. The battery reaction is shown below.

 The electromotive force is 1.8V.

This battery uses a carbon plastic electrode in which carbon black and graphite are mixed at a weight ratio of, for example, 6: 3: 1 in order to provide conductivity using polyethylene as a binder as an electrode material. On the surface of the positive electrode, a sheet made of activated carbon fibers such as carbon cloth is heat-sealed to reduce bromine reaction overpotential.

The electrolyte is provided in a tank provided separately from the battery main body, and is circulated by a pump so as to pass from the lower part to the upper part of the battery main body during charging and discharging. The bromine generated at the positive electrode by this circulation reacts with the bromine complexing agent (quaternary amine) added to the electrolyte to form an oily precipitate, which is returned to a separate tank and held at the bottom of the tank. It is sent into the cell by a pump and reduced.
Component of the electrolytic solution, NH ₄ Cl in order to reduce the resistance of the liquid to Z _n B _r2
Added salt etc., further to prevent the dendrite of the anode zinc, P _b to promote uniform electrodeposition, S _n, quaternary ammonium salts (dendrite inhibitor), and bromine complexing agent. A separator is provided between the positive electrode and the negative electrode to prevent bromine generated in the positive electrode from diffusing into the negative electrode and self-discharging with zinc.

The zinc-bromine battery has been developed as an electrolyte circulation type as described above. Considering a large-capacity stationary type for load leveling or the like, this is more advantageous, and the pump loss used for circulation is smaller than that of the whole battery. When the electrolytic solution tank is separately provided and the electrolytic solution is circulated, the distance between the electrodes of the cell body can be reduced, the concentration polarization of the electrochemical reaction can be reduced, and a highly efficient battery can be obtained.

D. Problems to be Solved by the Invention On the other hand, batteries as emergency power sources are required to have high reliability and safety. Therefore, when a conventional zinc-bromine battery is used as an emergency power source, a rotating body such as a pump is inferior in reliability, and piping required for circulation is also disadvantageous. Also, the manifold for sharing the electrolyte has a problem of shunt current. This is disadvantageous, for example, when charging is always performed such as floating charging. When a shunt current occurs, a dendrite is generated to cause a short circuit.

For the above reasons, when considering an emergency power supply, an electrolyte stationary battery is inevitably effective.

When the zinc / bromine battery is of the static electrolyte type, there is a problem that the electrolyte is injected into the cell and the concentration in the cell is not uniform. As one of the solutions to this problem, the applicant has previously proposed a nonwoven fabric impregnated with an electrolytic solution.

However, in this case, a step of placing the nonwoven fabric impregnated with the electrolytic solution on the electrode is necessary, which causes a problem in workability, and is not mass-produced. In addition, since dendrite grows at a probability almost equal to that of a normal liquid, the problem of dendrite generation remains.

In addition, since the positive electrode of the zinc / bromine battery is made of a sheet-like activated carbon fiber which is thermocompression-bonded so that the surface area is large and the flow is stable against the flow and falling off does not occur,
When this battery is commercialized, the cost of the positive electrode active layer increases.

In the case of a stationary battery, a sealed structure is inevitable in terms of reliability and maintainability. In this case, hydrogen gas (H ₂ ) may be generated from the negative electrode during charging. If the gas stays in the cell, problems such as a decrease in the effective area of the electrode, generation of dendrites due to current concentration, and liquid leakage due to an increase in internal pressure occur.

The present invention has been made in view of such a problem, and the object thereof is to make it possible to easily inject a battery and to keep bromine generated in the positive electrode near the electrode, An object of the present invention is to provide an inexpensive positive electrode active layer and an electrolyte stationary zinc-bromine battery capable of absorbing generated hydrogen.

E. Means for Solving the Problems In order to achieve the above object, carbon plastic electrodes are used for the positive and negative electrodes, and the positive electrode is provided with a positive electrode active layer,
In an electrolyte stationary zinc-bromine battery in which a positive electrode and a negative electrode are filled with an electrolytic solution containing a dendrite inhibitor or the like, silica is added to the electrolytic solution and a gel electrolyte is injected between the positive and negative electrodes. Liquid or coated on a non-woven fabric made of polyethylene or the like, provided between the positive and negative electrodes.

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

Alternatively, the hydrogen storage alloy powder may 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.

F. Action When silica is added to the electrolyte and the electrolyte is gelled,
The step of injecting liquid between the negative electrodes is facilitated. In addition, the addition of silica reduces the diffusion rate of bromine generated during charging and suppresses the increase in bromine concentration near the negative electrode, so that a battery with high electrical efficiency can be obtained without using a separator. Further, since the generated bromine is suppressed in sedimentation speed by the silica, the cell can be made a vertical type.

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

The hydrogen storage alloy powder is capable of storing hydrogen generated in the cell, and is filled with hydrogen generated in the cell.
The discharge cycle characteristics are stabilized for a long time.

G. Embodiment An embodiment of the present invention will be described with reference to the drawings.

First Embodiment FIG. 1 is a sectional view of a horizontal cell according to a first embodiment. First
In the figure, 1 is a positive electrode, 2 is a negative electrode, 3 is a positive electrode, a frame-shaped polyethylene packing provided between the negative electrodes 1 and 2, 4 is a gel electrolyte provided in a frame of the packing 3, 5 and 6 Reference numeral 7 denotes an FRP holding plate provided outside the positive and negative electrodes, and 7 denotes a screw for tightening the holding plates 5 and 6 inserted into a hole 8 formed in the peripheral portion of the holding plates 5 and 6.

The gelled electrolyte _{4, 3molZ n B r2 + 2molNH} 4 Cl + 1m
A solution obtained by adding 10 wt% of silica as a gelling agent to an electrolytic solution consisting of a ol bromine complexing agent and a dendrite inhibitor was used.
Silica was selected as the gelling agent because of consideration of bromine resistance. The silica used was Nipsil (trade name) E220A or G300 manufactured by Nippon Silica Kogyo. Gelation does not occur when 5 wt% of silica is added. Even if 10 wt% is added, there is fluidity, but it will be in a solid state if left standing. Therefore, in order to make the electrolytic solution into a gel state, it is necessary to add 10 wt% or more.

The batteries used in the characteristic tests were 5 cm x 5 cm, using positive and negative electrodes 1 and 2 made of carbon plastic. Distance between poles is 2mm
And Therefore, the amount of the electrolytic solution entering between them is 50 cc. Also the positive electrode 1 and the positive electrode active layer 10 to the plastic electrode, carbon cloth (Nippon Kynol manufactured by ACC-507 or 509, the specific surface area 1500~2000m ² / g, date amount 100 to 150 g / m ²⁾ obtained by laminating the Was used. Note that no separator was used in the electrolytic solution.

The positive electrode 1 and the packing 3 were placed on the holding plate 5, a gel electrolyte was poured into the frame of the packing 3, the negative electrode 2 was covered, the holding plate 6 was placed, and the periphery was tightened with screws 7.

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

Figure 3 is charging 1 hour at a charging current 20mA / cm ² (500mA), the discharge current 20 mA / cm ² in shows the charge and discharge voltage characteristics obtained by discharged to 1V / cell, electric quantity efficiency of about 65% It is. Without the use of a separator, this amount of electricity efficiency was obtained because the presence of silica reduces the bromine diffusion rate, and the bromine concentration near zinc does not increase, and the silica adsorbs bromine. It is presumed that bromine generated at the positive electrode stayed in the vicinity of the bromine electrode because of its action. On the other hand, the presence of silica increases the electrical resistance,
Voltage loss is increasing. The discharge initial voltage is 1.7V,
It is about 100 mV higher than when no silica is used. However, from the use of the emergency battery, this voltage loss can be dealt with by the number of stacked batteries, and such a loss does not affect the size increase when the number of stacked batteries is increased.

Fig. 3 shows a charge current of 20 mA / cm ² for 1 hour.
It shows the change in the electric energy efficiency with respect to the number of charge / discharge cycles repeated until the discharge end voltage reaches 1.0 V / cell at mA / cm ² , and there is almost no change in the efficiency over 100 cycles. After 100 cycles of charging, the battery was disassembled, but no dendrite was generated. Thereby, it was recognized that silica has a dendrite suppressing effect.

Second Embodiment FIG. 4 shows a cross section of a vertical cell according to a second embodiment.

This embodiment has a vertical configuration as shown in FIG. 4 with the battery configuration shown in FIG. This vertical battery was manufactured by first assembling the cell with one side edge of the frame packing 3 removed, and then fitting the one side edge with the gel-state liquid poured in and removed.

When the characteristics of this battery were examined under exactly the same conditions as in the test of the battery of the first example, the electricity efficiency was 50%. This is presumed to be lower than 65% of the horizontal type because the generated bromine precipitated to the lower part and the upper part of the electrode was not used effectively. However, this is a figure which can be sufficiently dealt with by improving the active layer, and it is assumed that the presence of silica slows down the sedimentation of bromine.

Third Embodiment FIG. 5 is a sectional view of a horizontal cell according to a third embodiment. Referring to FIG. 5, this embodiment shows a positive electrode 1 and a negative electrode 2 of the battery of FIG.
A low-cost commercially available polyethylene separator 11 having a thickness of 0.6 mm, which is used for a lead battery or the like, is provided between them.

When the characteristics of this battery were examined under exactly the same conditions as in the test of the battery of the first embodiment, the electricity efficiency was 75%, which was improved by 10% from 65% of the first embodiment.

Fourth Embodiment FIG. 6 is a cross-sectional view of a horizontal cell according to a fourth embodiment. In FIG. 6, 12 is silica + carbon black +
It is a gelled positive electrode active layer made of an electrolytic solution.

The positive electrode active layer 12, a silica in the electrolyte _{3molZ n B r2 + 2molNH 4 Cl} + 1mol bromine complexing agent + dendrite inhibitor
Add 20 Wt%, further add 5 Wt% of carbon black, and disperse it using a well shaker.
The coating was uniformly applied to a thickness of about 200 μmn to form a positive electrode active layer. The same silica as in Example 1 was used. The carbon black used was Lion Corporation Ketjen Black (trade name) EC.

Electrolyte solution 4 was prepared by adding 10 Wt% of silica to the above-mentioned electrolyte solution, and no separator was used. The electrode area, the distance between the electrodes, etc. are the same as those in the first embodiment. The electrode 1 provided with the electrolyte positive electrode layer is placed on the holding plate 5 made of FRP, and the frame-shaped packing 3 having a thickness of 2 mm is placed thereon. 4, the negative electrode 2, the holding plate 6 were placed in this order, and lightly tightened with the screw 7 to make it.

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

Fig. 7 shows a charge current of 20 mA / cm ² for 1 hour.
It shows the charge / discharge voltage characteristics when discharged to 1 V / cell at 20 mA / cm ² , and the characteristics were hardly changed from those of the first example shown by the dotted line.

FIG. 8 shows that the battery was charged for 1 hour at a charging current of 20 mA / cm ² and the charging current was 20
It shows the change in the electricity efficiency with respect to the number of repeated charge / discharge cycles of 1.0 V / cell at a discharge end voltage of mA / cm ² , and the efficiency is stable up to about 100 cycles as in the first embodiment. .

From these characteristics, it was found that the positive electrode active layer 11 had sufficient performance.

Fifth Embodiment FIG. 9 is a sectional view of a horizontal cell according to a fifth embodiment. Ninth
In the figure, reference numeral 13 denotes a hydrogen storage alloy powder that is dusted on the gel electrolyte 4.

Hydrogen storage alloy used (or abbreviated as HAA) is an alloy sample _{M m 95% N i3.5 C o0.7} Al 0.8 using Misch metal. Misch Memol is based on lanthanum 20%. The electrolyte 4 is _{3molZ n B r2 + 2molNH 4 Cl} + 1mol bromine complexing agent + silica in the electrolyte solution consisting of dendrite inhibitor
The positive electrode active layer 12, which is a gel having 10 wt% added thereto, was prepared by adding 5 wt% of carbon black to this electrolyte solution 4 to form a paste and apply it to the positive electrode. In the cell, the positive electrode is on the bottom and the negative electrode is on the top, and no separator is used. HAA used was in the form of a powder of about 500 μm to 1000 μm.

The preparation method is as follows. The electrode 1 coated with the positive electrode active layer 11 and the frame-shaped packing 3 are placed on the holding plate 5, the gel electrolyte 4 is put therein, and the HAA powder 13 is spread on the electrolyte 4. Negative electrode
2. It was made by mounting the holding plate 5 and fixing it with the screws 7.

 The test results of this battery are shown in FIG.

FIG. 10 shows that the charge efficiency was measured with respect to the number of charge / discharge cycles repeated until the discharge end voltage reached 1.0 V / cell at a charge current of 20 mA / cm ² for 1 hour at a charge current of 20 mA / cm ² . It shows a change, about 100 ~ when HAA is not added
Efficiency decreased at 150 cycles and an internal short circuit occurred at the end, but when HAA was added, the characteristics were stable up to about 300 cycles. It is considered that the hydrogen generated inside by this is occluded by HAA.

FIG. 11 shows a device for detecting the amount of hydrogen generated in a battery.
Is a liquid that does not gel so that gas can escape from the electrolyte well.
A battery with or without HAA powder is shown. twenty two
Is a sealed glass container containing a battery, 23 is a glass tube for taking out gas, 24 is a container containing water, 25 is a measuring cylinder for measuring the amount of gas emitted from the glass tube, and E is a DC power supply for charging the battery 20. .

FIG. 12 shows the change in the amount of repair gas measured by this measuring device. According to FIG. 12, when HAA was added to the negative electrode solution, almost no increase in gas volume was observed. Thus HAA is assumed to be occluded and H ₂ generated in the cell.

H. Effects of the Invention Since the zinc-bromine battery of the present invention is configured as described above, the following effects can be obtained.

Since the electrolytic solution was made into a paste by adding silica to the electrolytic solution, the step of injecting the liquid between the cell electrodes becomes easy.

Also, the addition of silica decreases the bromine diffusion rate,
Since the increase in the bromine concentration near the negative electrode is suppressed, the electricity efficiency of 65% or more is possible without using a separator. Further, silica not only suppresses the diffusion speed of bromine but also has an action of adsorbing bromine, so that bromine generated in the positive electrode can be kept near the positive electrode.

Addition of silica is effective in suppressing dendrite.

In the invention of claim (1), since the sedimentation speed of bromine generated by the silica is suppressed, the cell can be of a vertical type.

According to the invention of claim (2), the same properties as the conventional activated carbon fiber can be obtained by applying a paste obtained by adding carbon black to a gel electrolyte solution containing silica as a positive electrode active layer to the positive electrode. Obtained. Thereby, the cost of the positive electrode active layer can be reduced.

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

In addition, since the positive electrode active layer does not move and the positive electrode faces downward and does not fall off, sufficient performance of cycle characteristics can be obtained.

According to the invention of claims (3) and (4), hydrogen generated in the cell can be stored in the hydrogen storage alloy added to the electrolyte. This greatly improves the charge / discharge cycle characteristics. In addition, it is possible to prevent liquid leakage to the outside due to an increase in internal pressure due to the generated gas.

[Brief description of the drawings]

FIG. 1 is a sectional view of a horizontal cell showing a first embodiment, FIG. 2 is a charge / discharge voltage characteristic curve of the cell, and FIG. 3 is a charge / discharge cycle characteristic curve of the 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 cell of the fourth embodiment. FIG. 8 is a charge / discharge cycle characteristic curve of the 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 cell. FIG. 11 is a curve diagram showing a device for detecting the amount of hydrogen generated in a battery, and FIG. 12 is a curve diagram showing the amount of gas for repairing a battery by the device. DESCRIPTION OF SYMBOLS 1 ... Positive electrode, 2 ... Negative electrode, 3 ... Packing, 4 ... Electrolyte holder, 5, 6 ... Pressing plate, 10, 12 ... Positive electrode active layer, 11, 2
1… Separator, 13… Hydrogen storage alloy (HAA).

Claims (4)

(57) [Claims] 1. A positive and negative electrode using a carbon plastic electrode, a positive electrode active layer provided on the positive electrode surface, and an electrolyte containing a dendrite inhibitor added between the positive and negative electrodes is filled and sealed. In a zinc-bromine type battery, silica is added to the electrolyte and the mixture is injected as a gel electrolyte between the positive and negative electrodes or coated on a nonwoven fabric made of polyethylene or the like and provided between the positive and negative electrodes. Electrolyte stationary zinc-bromine battery. 2. An electrolyte stationary zinc-bromine battery in which a carbon plastic electrode is used for the positive and negative electrodes, a positive electrode active layer is provided on the positive electrode surface, and a dendrite inhibitor is added between the positive and negative electrodes. Along with adding silica to a gel electrolyte, an electrolyte prepared by adding silica and carbon black to the electrolyte as the positive electrode active layer is applied to a positive electrode, and the negative electrode is placed with the positive electrode on the lower side. Provided on the upper side,
An electrolyte stationary zinc-bromine battery characterized in that no separator is provided between the positive and negative electrodes. 3. An electrolyte solution comprising a carbon plastic electrode for the positive and negative electrodes, a positive electrode active layer provided on the surface of the positive electrode, an electrolyte solution containing a dendrite inhibitor added between the positive and negative electrodes, and sealing. A zinc-negative electrode, wherein silica is added to the electrolyte to form a gel electrolyte, a negative electrode is provided on the upper side with the positive electrode on the lower side, and a hydrogen storage alloy powder is provided near the negative electrode of the gel electrolyte. And an electrolyte stationary type zinc-bromine battery. 4. The positive electrode active layer is formed by thermocompression-bonding activated carbon fibers to an electrode, or by applying a paste formed by adding carbon black to a gelled electrolyte. Item (3): An electrolyte stationary zinc-bromine battery according to item (3).