JP2002216833A - Redox cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light and small-sized redox cell having high output characteristics and a charging method of the cell. SOLUTION: The redox cell is of static liquid type not equipped with an electrolyte solution storage tank but is equipped at least with a diaphragm, a positive side electrolyte solution tank, a negative side electrolyte solution tank, a positive side bipolar plate, a negative side bipolar plate, a metal plate which has a positive electrode terminal and a metal plate which has a negative electrode terminal. And the positive side electrolyte solution tank and the negative side electrolyte solution tank are filled with a mixture of electrolyte solution including vanadium ion, as an active material, and powder or small pieces of conductive matters, as electrodes. The electromotive force of the redox cell, when it declines, is restored to the initial state by the charging method of changing the polarity of electrodes alternately and applying a voltage from outside.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a static redox battery having no electrolyte storage tank and a method for charging the same.

[0002] In the present specification, a battery that performs charge and discharge by utilizing the oxidation / reduction reaction of ions (so-called redox ions) that can take at least two or more oxidation states in an electrolytic solution is referred to as a “redox battery”. Collectively, the redox battery includes a “redox flow battery”, which is characterized by circulating and supplying an electrolytic solution to a flow-type electrolytic cell.

[0003]

2. Description of the Related Art In recent years, the liberalization of electric power has started, and it is said that a stable supply of high-quality electric power as in the past cannot be expected in the future, and that it is necessary for consumers to take measures against power outages.

At present, various batteries have been developed for power failure countermeasures, and capacitors are mainly used for momentary power failures, and lead batteries are mainly used for several minutes of power failures.

[0005] However, since the capacitor ends discharging instantaneously, it can usually cope only with an instantaneous power failure within 2 seconds, and there is a problem that its application range is narrow. Although a lead battery can cope with a power outage of 1 to 2 minutes, the electrode itself deteriorates due to repeated charging and discharging, and thus has a problem that its service life is about 2 to 3 years and cannot be used for a long time. Furthermore, it has been pointed out that waste such as lead, which has a large environmental load, is generated when disposed after use.
In view of such a problem, a redox flow battery has recently been receiving attention as a battery that can be used for power failure countermeasures.

A redox flow battery circulates and supplies two kinds of electrolytes (aqueous redox solution) stored in a tank to a flow-type electrolytic cell by a pump or the like, and utilizes an oxidation / reduction reaction of an active material contained in the electrolyte. This is a battery that performs discharge. That is, since the redox flow battery uses the valence change of the active material as a power generation principle, there is almost no electrode deterioration with time as seen in a lead battery, and long-term use is possible.
Also, by changing the size of the electrolyte storage tank,
It is also possible to respond widely to power outages of about a minute to two hours. Therefore, it can be said that the redox flow battery is an excellent battery that solves the above-mentioned problems such as the capacitor and the lead battery.

However, the redox flow battery has the following disadvantages.

[0008] Since auxiliary equipment such as a pump is required for the circulating supply of the electrolyte, the battery device is inevitably large in scale. Therefore, miniaturization is difficult and it is not suitable for home use.

When the positive electrode electrolyte and the negative electrode electrolyte each contain ions of different elements (for example, one contains iron ions and the other contains chromium ions), after the long-term operation, the different elements are passed through the membrane. Since the ions are mixed, the discharge output decreases. Therefore, it is necessary to periodically replace each electrolytic solution in the tank with a new one in order to recover the discharge output.

Recently, as a solution to the above-mentioned drawbacks of the redox flow battery, for example, an all-vanadium redox flow battery (see Japanese Patent Application Laid-Open No. 62-186473).
Has been proposed. This battery is characterized in that both active materials of two kinds of electrolytes used in a redox flow battery are vanadium ions. This battery is said to be free from mixing of different element ions through the diaphragm, and to be able to be used many times by rebalancing the circulating electrolyte.

A redox capacitor has been proposed by Nozaki et al. (Refer to the 39th Battery Symposium 3B05). This battery discharges for a short time using only the electrolytic solution previously filled in the electrolytic cell, and has no auxiliary equipment such as a pump, so that it can be miniaturized.

Further, for example, Japanese Patent Application Laid-Open No. H11-329474
In order to reduce the contact resistance between the electrode and the bipolar plate of the redox flow battery, Japanese Patent Application Laid-Open Publication No. H11-15064 discloses a method of firmly tightening the battery device from both ends with a holding plate such as an iron plate. However, these various remedies do not comprehensively remedy the disadvantages of redox flow batteries. further,
These remedies also create new problems, such as:

For example, in an all-vanadium redox flow battery, it is necessary to increase the vanadium ion concentration of the electrolyte in order to increase the battery output. However, the electrolyte having a high vanadium ion concentration has a high viscosity and is difficult to circulate. Become. In the redox capacitor, in order to reduce the contact resistance between the diaphragm, the electrode plate, and the bipolar plate, a material having high elasticity and high bulk density must be used as the electrode material. At the same time, as a bipolar plate,
That is, it is necessary to use a material having a high surface accuracy, and there is a problem that the manufacturing cost is increased. Further, Japanese Patent Application Laid-Open
In the technique disclosed in Japanese Patent Application Laid-Open No. 329474, the weight increase due to the installation of an auxiliary tool such as a holding plate becomes a problem.

[0014]

From the above viewpoints, there is a strong demand for the development of a redox battery having a light weight, a small size and a high output performance as compared with the conventional redox battery. Has not yet been developed.

Accordingly, an object of the present invention is to provide a redox battery which is particularly lightweight and compact and has high output performance. Another object of the present invention is to provide a method for charging the redox battery.

[0016]

The present inventor has conducted intensive studies to solve the problems of the prior art, and as a result, has found that a liquid static redox battery having a specific structure achieves the above object. Finally, the present invention has been completed.

That is, the present invention relates to the following redox battery and its charging method.

1. A liquid static type redox battery having no electrolyte storage tank, at least a diaphragm, a positive electrode-side electrolytic cell, a negative electrode-side electrolytic cell, a positive electrode-side bipolar plate, a negative electrode-side bipolar plate, a metal plate having a positive electrode terminal and a negative electrode terminal. A metal plate having a positive electrode-side electrolytic cell and a negative electrode-side electrolytic cell filled with a mixture of an electrolytic solution containing vanadium ions as an active material and a powder or a small piece of a conductive material as an electrode. Redox battery.

2. 2. The redox battery according to the above item 1, wherein a mixture of a carbon powder or a small piece subjected to a hydrophilic treatment and a carbon powder or a small piece not subjected to a hydrophilic treatment is used as the conductive substance powder or the small piece.

3. Item 1 wherein the contact area with the electrolytic solution is increased by providing irregularities on the surface of the bipolar plate.
Or the redox battery according to 2.

4. Any of the above items 1 to 3, wherein a ratio (Sc / S) of a surface area (Sc) of the bipolar plate in contact with the electrolytic solution to a cross-sectional area (S) of the bipolar plate in a surface in contact with the electrolytic solution is 1 to 100. A redox battery according to any of the claims.

5. 5. The method according to any one of the above items 1 to 4, wherein when the electromotive force decreases due to the fatigue of the electrolyte, the electromotive force is restored to an initial state by switching the polarity of the electrodes and applying a voltage from outside. Redox battery charging method.

[0023]

BEST MODE FOR CARRYING OUT THE INVENTION The redox battery of the present invention is a liquid static type redox battery, in which a positive electrode-side electrolytic cell and a negative electrode-side electrolytic cell contain an electrolytic solution and a powder or a small piece of a conductive substance as an electrode. (Hereinafter, the mixture is referred to as “electrode mixed electrolyte” to distinguish the mixture from “electrolyte”). Hereinafter, the redox battery of the present invention having the above characteristics will be described.

The electrode in the present invention uses a powder or a small piece of a conductive substance. Type conductive material is not particularly limited, there is not dissolved in the electrolyte solution at least used, it is preferable to use those having a 10 ^-2 S / cm or more electrical conductivity. The size of the powder or the small pieces is not particularly limited, and can be appropriately set in consideration of the surface properties of the conductive substance, the size of the electrolytic cell, and the like. Preferably 0.
It is about 5 to 1 mm.

In the present invention, it is preferable to use a carbon powder or a small piece as a powder or a small piece of the conductive substance having the above-mentioned characteristics, and more preferably to use a hydrophilically treated carbon powder or a small piece with a hydrophilic treatment. It is to use a mixture with untreated carbon powder or flakes. When the mixture is used, the wettability of the carbon surface with the electrolytic solution is improved, and the battery efficiency can be further improved.

The type of the carbon powder or small pieces is not particularly limited, and any known or commercially available carbon powder can be used as long as it corresponds to the size described above. Further, for example, a commercially available carbon felt, carbon knitted fabric, carbon woven fabric, or the like processed into a powder or a small piece having the above-described size according to a conventional method may be used. In the present invention, carbon powder (trade name “KF Felt” manufactured by Toyobo Co., Ltd.) was particularly processed into a powder or a small piece of the above size using a known cutting tool such as a cutter. Can be suitably used.

The type of the carbon powder or small pieces subjected to the hydrophilic treatment is not particularly limited, and any known or commercially available carbon powder can be used as long as it corresponds to the above-mentioned size.
Further, carbon powder or small pieces which have been subjected to hydrophilic treatment according to a conventional method may be used. In the present invention, as the carbon powder or the small pieces subjected to the hydrophilic treatment, the carbon felt particularly subjected to the hydrophilic treatment (product number “TKSVRF-CF004” manufactured by Toyobo Co., Ltd.) is used by using a known cutting tool such as a cutter. What has been processed into a powder or a small piece of the size can be suitably used.

When a mixture of the hydrophilically treated carbon powder or small pieces and the non-hydrophilically treated carbon powder or small pieces is used, the mixing ratio is not particularly limited. It is preferable that about 1 part by weight of a carbon powder or a small piece not subjected to the hydrophilic treatment is mixed with 5 parts by weight of the powder or the small piece.

When the carbon surface is subjected to hydrophilic treatment, the method of hydrophilic treatment is not particularly limited. As one of suitable hydrophilic treatment methods, for example, under an oxygen atmosphere having an oxygen partial pressure of 1 × 10 ⁻² torr or more, the carbon surface is heated to 400 ° C. or more to perform a dry oxidation treatment to thereby reduce the carbon surface. A method of performing a hydrophilic treatment can be given.

When the powder or the small piece of the conductive substance is filled in the positive electrode side electrolytic cell and the negative electrode side electrolytic cell, a necessary amount of the conductive substance powder or the small piece is sufficiently mixed in advance with the positive electrode electrolyte and the negative electrode electrolyte. It is preferable to prepare an electrode mixed electrolytic solution and fill the electrolytic mixed solution into each electrolytic cell. The amount of the conductive substance powder or small pieces mixed with each electrolytic solution is not particularly limited, but it is generally preferable to mix about 4 parts by weight of the conductive substance powder or small pieces with 9 parts by weight of the electrolytic solution.

The electrolyte used in the redox battery of the present invention contains vanadium ions as an active material. The concentration of vanadium ions contained in the electrolyte is not particularly limited,
Usually, it is preferably about 0.1 to 5 mol / l, more preferably about 1 to 2 mol / l. If the concentration of vanadium ions is less than 0.1 mol / l, the energy density of the battery may decrease. In addition, 5mol / l
If it exceeds 300, the viscosity of the electrolytic solution becomes excessively high, and the wettability of the electrode surface may be deteriorated. In order to increase the battery efficiency of the redox battery, it is preferable that the vanadium ion concentration in the positive electrode electrolyte and the vanadium ion concentration in the negative electrode electrolyte are the same.

The electrolytic solution used in the present invention, as the positive electrode electrolyte in particular, it is preferable to use an aqueous solution containing a vanadium ion V ⁴⁺ / V ^5+, of the V ⁴⁺ / V ⁵⁺ It is preferable to use a sulfuric acid aqueous solution containing V ⁴⁺ / V ⁵⁺ vanadium ions in view of the stability, solubility, and charge / discharge reaction rate of vanadium ions.

[0033] As the negative electrode electrolyte solution, it is preferable to use an aqueous solution containing a vanadium ion V ²⁺ / V ^3+, stability of vanadium ions of the V ²⁺ / V ^3+, solubility, charge and discharge From the viewpoint of reaction rate, it is preferable to use a sulfuric acid aqueous solution containing V ²⁺ / V ³⁺ vanadium ions.

When the above-mentioned aqueous sulfuric acid solution containing vanadium ions is used, the concentration of the sulfuric acid ions in the aqueous sulfuric acid solution is usually 0.1 to 5 mol for both the positive electrode electrolyte and the negative electrode electrolyte.
about 1 / l, more preferably 1-2 mol /
It is about l. If the sulfate ion concentration is less than 0.1 mol / l or more than 5 mol / l, vanadium may be precipitated in both cases. When an aqueous solution of sulfuric acid is used, it is preferable that the concentration of sulfate ion in each electrolyte is the same in order to improve the battery efficiency of the redox battery.

Incidentally, various ion stabilizers may be added to the electrolytic solution used in the present invention, if necessary. Preferable examples of the ion stabilizer to be added include a pentavalent vanadium ion stabilizer. In the present invention, by adding the ion stabilizer, 5
Vanadium pentoxide (V)
₂ O ₅ ) can be reliably prevented from being precipitated.

As the pentavalent vanadium ion stabilizer, a phosphoric acid type stabilizer is preferable, for example, sodium pyrophosphate, potassium pyrophosphate, sodium polyphosphate,
It is preferable to use sodium tripolyphosphate, sodium hexametaphosphate and the like. These phosphate stabilizers can be used alone or in combination of two or more.

When the ion stabilizer is added, the amount thereof is not particularly limited, but is usually 0.0003 mol to 0.2 m per 1 mol of vanadium ion in the electrolytic solution.
ol is preferred, more preferably 0.0005mo
It is about 1 to 0.08 mol. The amount of the phosphoric acid-based stabilizer to be added is 0.1 to 1 mol of vanadium ions in the electrolytic solution.
When the amount is less than 0003 mol, the effect of preventing precipitation of the vanadium compound at a high temperature may not be sufficiently obtained.
If the amount exceeds 0.2 mol, the charge / discharge efficiency of the redox battery may decrease.

The redox battery of the present invention has a positive bipolar plate and a negative bipolar plate. The installation place is not particularly limited, but it is usually preferable to install them on the opposite side of the diaphragm across the electrolytic cell. In the present invention, it is particularly preferable to form the wall surface of the electrolytic cell together with the diaphragm.

The material of the bipolar plate is not particularly limited as long as it is a material excellent in electric conductivity and electrochemical stability and does not dissolve in the electrolytic solution. For example, gold, platinum, platinum, rhodium, Metal such as tantalum or plastic carbon can be used, and among them, it is particularly preferable to use plastic carbon from the viewpoint of cost. As the form of the bipolar plate, a metal sheet, a metal foil, a plastic carbon sheet, or the like obtained by processing the above metal or plastic carbon can be suitably used.

Although the thickness of the bipolar plate is not particularly limited,
Usually, it is preferably about 1 to 15 mm, more preferably 1 to 15 mm.
It is about 4 mm. When the thickness of the bipolar plate is less than 1 mm, the bipolar plate may be deformed due to pressure fluctuation of the electrolyte.
On the other hand, if it exceeds 15 mm, the electric resistance increases, and the battery efficiency may deteriorate.

In the redox battery of the present invention, since the electrode shape is no longer a sheet shape, the surface properties of the bipolar plate are not limited to those having a high surface accuracy such as the bipolar plate conventionally used in a redox flow battery. Rather, it is preferable to increase the contact area with the electrolytic solution by providing irregularities on the surface of the bipolar plate. In the present invention, bipolar efficiency and battery efficiency can be improved by increasing the contact area with the electrolytic solution.

The amount of increase in the surface area due to the provision of the irregularities is not particularly limited. For example, the ratio of the surface area (Sc) of the bipolar plate in contact with the electrolytic solution to the cross-sectional area (S) of the bipolar plate in contact with the electrolytic solution (Sc / S) is preferably in the range of 1 to 100.

There is no particular limitation on the method of forming the irregularities on the bipolar plate. For example, a method of forming the desired irregularities by pressing the bipolar plate on a mold having irregularities is preferable.

The membrane used for the redox battery of the present invention is not particularly limited, and known or commercially available ion exchange resins can be used. Among the ion exchange resins, those having particularly high proton permeation performance, vanadium ion It is preferable to use a material which can suppress the permeation of the material and a material having excellent oxidation resistance.

Examples of the ion exchange resin having the above-mentioned properties include ion exchange resins having a cation exchange group such as a sulfonic acid group, a carboxylic acid group, a phosphonic acid group, and a phosphinic acid group, a pyridinium base, and a quaternary ammonium. It is preferable to use an ion exchange resin having an anion exchange group such as a base, a tertiary amine group, and a phosphonium group. In the present invention, among these, an ion exchange resin having a pyridinium group having particularly high proton permeation performance can be suitably used.

The resin into which the ion exchange group is introduced is not particularly limited, but usually, a crosslinked polymer resin of a vinyl polymerizable monomer, a polysulfone resin, a Teflon (registered trademark) resin or the like is preferable.

Although the thickness of the diaphragm in the present invention is not particularly limited, it is usually preferably about 100 to 3000 μm, more preferably 200 to 2000 μm. If the thickness of the diaphragm is less than 100 μm, the strength and durability may not be sufficient. If it exceeds 3000 μm, the charge / discharge efficiency may decrease.

The redox battery of the present invention has a positive electrode side electrolytic cell and a negative electrode side electrolytic cell, and the electrolytic cell is filled with an electrode mixed electrolytic solution. Although the configuration of each electrolytic cell is not particularly limited, the redox battery of the present invention is preferably a cell surrounded by a diaphragm, an electrolytic cell frame, and a bipolar plate.

The material of the electrolytic cell frame is not particularly limited, and various materials including those conventionally used for electrolytic cells of redox flow batteries can be used. Among them, it is preferable to use a synthetic resin. For example, when using polyvinyl chloride or the like, it is preferable because the weight of the redox battery can be reduced.

The volume of the electrolytic cell is not particularly limited and can be appropriately set according to the desired battery performance.
In order to continuously supply electric power of about Wh for one hour, the volume of each electrolytic cell may be set to preferably about 0.2 to 1.6 m ³ , more preferably about 0.5 to 1.2 m ³ . In addition, it is preferable that the capacity of the positive electrode side electrolytic cell and the negative electrode side electrolytic cell be the same from the viewpoint of the stability of the battery efficiency.

The redox battery of the present invention has a metal plate having a positive terminal and a metal plate having a negative terminal as its constituent parts. There are no particular restrictions on their installation,
Usually, it is preferable to provide it outside the positive electrode side bipolar plate and the negative electrode side bipolar plate so as to be in contact with them.

The material of the metal plate is not particularly limited as long as it is excellent in electric conductivity. For example, copper, gold, rhodium, platinum, silver and the like can be used. Among them, it is particularly preferable to use copper from the viewpoint of cost.

Although the thickness of the metal plate is not particularly limited,
Usually, it is preferably about 0.1 to 10 mm, more preferably about 2 to 5 mm. If it is less than 0.1 mm, deformation may occur due to pressure fluctuations in the electrolytic cell. Also, 10m
If it exceeds m, the weight of the battery may increase.

Each pole terminal is preferably used by being connected to a wire terminal of various external devices, and its size, shape, and the like can be appropriately set.

The method for assembling the redox battery of the present invention is not particularly limited. As an example of a suitable assembling method, for example, a component on the positive electrode side (a metal plate having an electrolytic cell frame, a bipolar plate and a pole terminal) and a component on the negative electrode side (a metal plate having an electrolytic cell frame, a bipolar plate and a pole terminal) ), A positive electrode-side electrolytic cell and a negative electrode-side electrolytic cell are prepared in advance, and then each electrolytic cell is filled with an electrode mixed electrolytic solution, and then the two are joined together with a diaphragm interposed therebetween. Various adhesives, bolts, and the like can be used to connect the components.
After assembling the redox battery, it is also preferable to cover and reinforce the entire battery with various synthetic resins.

The charging timing and the charging method of the electrode mixed electrolyte are not limited to the above-described method. For example, it is also possible to provide a filling hole in at least one of the electrolytic cell frame, the bipolar plate and the pole terminal, and to inject the electrode mixed electrolyte from the filling hole after assembling the redox battery. After filling, the filling hole may be closed with a screw having rubber packing, for example.

The method of installing the redox battery of the present invention, the installation place, and the like are not particularly limited. Since the redox battery of the present invention is of a liquid stationary type, it is not necessary to always install it horizontally as long as each electrolytic cell itself is sufficiently sealed, and it can be used in a desired installation method.

In the redox battery of the present invention, when the electromotive force decreases due to the fatigue of the electrolyte, the electromotive force is restored to the initial state by switching the polarity of the electrodes and applying a voltage from the outside. Although the external power source is not particularly limited to be used during charging, for example, the electrode area of 1 cm ² per 70
The one that can supply a DC power of about mA is preferable. The “electrode area” in the present invention is a diaphragm area of a portion in contact with the electrolytic solution, in other words, a diaphragm area of a portion to which protons in the electrolytic solution can move.

During charging, it is preferable to install a voltage measuring device such as a battery voltage monitor on the redox battery. In the redox battery of the present invention, charging is preferably terminated when the battery voltage is about 1.55V. If the charge is excessive, side reactions such as electrolysis of water contained in the electrolytic solution may occur.

[0060]

In the following, an aqueous sulfuric acid solution containing V ⁴⁺ / V ⁵⁺ vanadium ions is used as a positive electrode electrolyte, and V ^{2+ is} used as a negative electrode electrolyte.
The change of the active material in each electrolytic solution at the time of charge / discharge reaction when using a sulfuric acid aqueous solution containing vanadium ions of / V ³⁺ will be described.

In the positive electrode electrolyte, V ⁴⁺
→ The oxidation reaction represented by V ⁵⁺ + e ⁻ proceeds. That is, the positive electrode electrolyte may take a mixed state of tetravalent and pentavalent vanadium ions or a state of pentavalent vanadium ions alone in the charged state. 5 in the cathode electrolyte at the end of charging
The ratio of the vanadium ion concentration to the total vanadium ion concentration is usually preferably about 70 to 85%,
More preferably, it is 80 to 85%.

On the other hand, in the discharge state, V ⁵⁺ + e
^- → represented by the reduction reaction in the V ⁴⁺ to proceed. The concentration of tetravalent vanadium ions in the positive electrode electrolyte at the end of the discharge,
The ratio to the total vanadium ion concentration is usually 70 to
It is preferably about 95%, more preferably 80 to 90%.

The chemical reactions involved in the charge / discharge reaction when the above-mentioned sulfuric acid aqueous solution is used as the positive electrode electrolyte are as follows.

[0064]

Embedded image In the negative electrode electrolyte, V ³⁺ + e ⁻ → V ^{2+ in the} charged state
The reduction reaction represented by That is, the negative electrode electrolyte is
In the charged state, a mixed state of trivalent and divalent vanadium ions or a state of divalent vanadium ions alone can be taken. The ratio of the divalent vanadium ion concentration in the negative electrode electrolyte to the total vanadium ion concentration at the end of charging is usually preferably about 70 to 95%, more preferably 80 to 90%.

On the other hand, in the discharge state, V ²⁺ → V
³⁺ + e ^- oxidation reaction proceeds represented by. The concentration of trivalent vanadium ions in the positive electrode electrolyte at the end of the discharge,
The ratio to the total vanadium ion concentration is usually 70 to
It is preferably about 90%, more preferably 75 to 85%.

The chemical reaction in the charge / discharge reaction when the above-mentioned aqueous sulfuric acid solution is used as the negative electrode electrolyte is as follows.

[0067]

Embedded image

[0068]

According to the invention described in claim 1 of the present application,
There is no need to circulate the electrolyte in the electrolytic cell. Accordingly, it is not necessary to install auxiliary equipment such as an electrolyte storage tank and a pump, and a light and small redox battery can be manufactured.

Since the electrolyte is not circulated, a high-viscosity high-concentration vanadium solution can be used as the electrolyte.
Therefore, it is possible to manufacture a redox battery having high output performance while being lightweight and compact.

Furthermore, since a powder or a small piece of a conductive substance is used as an electrode, it is not necessary to separately provide a sheet-like electrode as in the related art. Therefore, the production of a redox battery is easy, and the surface area of contact with the electrolyte is increased by making the bipolar plate, which had conventionally been required to have high surface accuracy in order to make it adhere to the sheet-like electrode, more uneven, thereby increasing the surface area. It has become possible to improve efficiency.

In addition, since the bipolar plate and the sheet-like electrode are no longer in contact with each other by sandwiching the bipolar plate and the sheet-like electrode from each other, a pressing plate for pressing both sides of the stack, which is preferably used in a conventional redox flow battery, is unnecessary. Therefore, the entire battery can be made of a synthetic resin such as polyvinyl chloride, so that it is possible to further reduce the weight and facilitate the manufacture.

According to the invention as set forth in claim 2 of the present application, by mixing the carbon powder or the small pieces subjected to the hydrophilic treatment with the carbon powder or the small pieces not subjected to the hydrophilic treatment, the carbon surface or the electrolytic solution can be further increased. And the battery efficiency can be improved.

According to the third and fourth aspects of the present invention, when the surface area of the bipolar plate is increased, the bipolar efficiency can be improved and the output of the battery can be increased.

According to the invention as set forth in claim 5 of the present application, when the electromotive force is reduced due to the fatigue of the electrolyte, the polarity of the electrodes is switched to each other and a voltage is applied from the outside to reduce the electromotive force. It is possible to restore to the initial state. Therefore, since the same electrolyte can be repeatedly charged and used, it is excellent in long-term use stability and environmental preservation.

[0075]

The present invention will be specifically described below with reference to examples. However, the present invention is not limited to the scope of these descriptions.

Example 1 Preparation of Redox Battery (Miniature Cell) A miniature cell was prepared by fixing a diaphragm, an electrolytic cell frame made of polyvinyl chloride, a bipolar plate made of plastic carbon, and a copper plate having pole terminals with bolts or an adhesive, respectively. . The size of the electrolytic cell frame used is such that the size of each electrolytic cell (net size to be filled with the electrode mixed electrolyte) is 30 mm long and 3 mm wide.
0 mm, thickness (part corresponding to the distance between diaphragm and bipolar plate)
One having a size of 5.4 mm was used.

The filling amount of the electrode mixed electrolytic solution is determined by the electrolytic cell on the positive electrode side,
The negative electrode side electrolytic cell was about 5 cc. The electrode mixed electrolyte used was prepared according to the following method. [Preparation of Electrode Mixed Electrolyte] 4 g of carbon felt subjected to hydrophilic treatment (product number “TKSVRF-CF004” manufactured by Toyobo Co., Ltd.) and carbon felt not subjected to hydrophilic treatment (trade name “KF Felt” manufactured by Toyobo Co., Ltd.) After processing 6 g of each into small pieces of 3 mm in size using a cutter, both were mixed until uniform. Next, both the tetravalent vanadium ion concentration and the sulfate ion concentration were 2 mol /
1 vanadium sulfate aqueous solution (positive electrode electrolyte);
Valent vanadium ion concentration and sulfate ion concentration are both 2
mol / l vanadium sulfate aqueous solution (negative electrode electrolyte)
Were prepared in an amount of about 5 cc, and 5 g of each of the above-mentioned mixture of electrode pieces was added thereto. After the addition, the mixture was sufficiently stirred until the electrode pieces were uniformly dispersed to prepare an electrode mixed electrolyte on the positive electrode side and an electrode mixed electrolyte on the negative electrode side.

[0078] Redox batteries prepared by charging the method of Example 2 redox batteries, 70 mA /
It was charged with a constant current of cm ² × 9cm ^2. That is, the electrode area is 9cm ^2, 70 mA per electrode area 1 cm ²
An external power supply capable of supplying a direct current was used. Redox batteries include a digital oscilloscope (Model No. "DL708
E ", manufactured by Yokogawa Electric Corporation, and charged while monitoring the battery voltage. The battery voltage was 0.6 V at the start of charging, and the charging was terminated after confirming that the battery voltage reached 1.55 V. The time required to complete charging was 20 minutes. Experimental Example 1 A digital oscilloscope (part number "DL70") was prepared in Example 1 and charged to the redox battery charged by the method of Example 2.
8E "manufactured by Yokogawa Electric Corporation.
^The battery was discharged at a constant current of ² (rated current; no overload), and the change in battery voltage over time was measured. Laboratory temperature is 25
° C. FIG. 2 shows the change in the battery voltage over time obtained by the measurement.

EXPERIMENTAL EXAMPLE 2 The same measurement as in Experiment 1 was performed by changing the value of the constant current to be discharged to 120 mA / cm ² (overload current). FIG. 2 shows the change in the battery voltage over time obtained by the measurement.

EXPERIMENTAL EXAMPLE 3 The same measurement as in Experiment 1 was performed by changing the value of the constant current to be discharged to 180 mA / cm ² (overload current). FIG. 2 shows the change in the battery voltage over time obtained by the measurement.

[Experimental Results] From the graph of the battery voltage over time shown in FIG. 2, it can be seen that the discharge time is shortened with an increase in the discharge current. It turns out that it is. In addition, the redox battery of the present invention has a short-term power outage of about one minute,
It was found that an output more than three times the rated output was possible. This experiment is a miniature model in which only about 5 cc of the electrolytic solution is filled in each electrolytic cell. If the amount of the filled electrolytic solution is increased, discharge for about 1 hour is possible.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a configuration of one embodiment of a redox battery of the present invention.

FIG. 2 is a graph showing changes in battery voltage over time obtained in Experimental Examples 1 to 3.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Whole redox battery 2A Positive electrode bipolar plate 2B Negative electrode bipolar plate 3A Positive electrode electrolytic cell 3B Negative electrode electrolytic cell 4A Positive electrode mixed electrolyte 4B Negative electrode mixed electrolyte 5 Separator 6A Metal plate having a positive electrode terminal 6B Metal plate with negative terminal

Claims (5)

[Claims] 1. A liquid static type redox battery having no electrolyte storage tank, comprising at least a diaphragm, a positive electrode side electrolytic cell,
A negative electrode-side electrolytic cell, a positive electrode-side bipolar plate, a negative electrode-side bipolar plate, a metal plate having a positive electrode terminal and a metal plate having a negative electrode terminal, and vanadium as an active material in the positive electrode-side electrolytic cell and the negative electrode-side electrolytic cell; A redox battery filled with a mixture of an electrolyte solution containing ions and a powder or a small piece of a conductive substance serving as an electrode. 2. The redox battery according to claim 1, wherein a mixture of a carbon powder or a small piece subjected to hydrophilic treatment and a carbon powder or small piece not subjected to hydrophilic treatment is used as the conductive substance powder or small piece. 3. The redox battery according to claim 1, wherein the surface of the bipolar plate is provided with irregularities to increase the contact area with the electrolyte. 4. A ratio (Sc / S) of a surface area (Sc) of the bipolar plate in contact with the electrolytic solution to a cross-sectional area (S) of the bipolar plate in a surface in contact with the electrolytic solution is 1 to 100. The redox battery according to any one of claims 1 to 3. 5. The electromotive force is restored to an initial state by switching the polarity of the electrodes and applying a voltage from the outside when the electromotive force decreases due to the fatigue of the electrolyte.
A method for charging a redox battery according to any one of claims 1 to 4.