JP2994337B1 - Method for regenerating electrolyte solution for all vanadium redox flow batteries - Google Patents

Abstract

A main object of the present invention is to provide a method for regenerating an electrolyte of a redox flow battery, which does not require a large amount of an electrolyte for regeneration and does not require a complicated electrolyte regenerating apparatus. And SOLUTION: The above-mentioned imbalance is corrected by adding, to a positive electrode electrolyte in an unbalanced discharge state, trivalent vanadium in an amount substantially equal to 1/2 of the above-mentioned imbalance.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention generally relates to a method for regenerating an electrolyte solution of an all-vanadium redox flow battery, and more specifically, to regenerate an electrolyte solution in an unbalanced discharge state. And a method for regenerating the electrolyte of an all-vanadium redox flow battery improved so that the amount of the electrolyte can be reduced.

[0002]

2. Description of the Related Art Japan's power demand has been increasing year by year, but fluctuations in power demand have tended to increase year by year, reflecting the sophistication of the industrial structure and the improvement of the standard of living of the people. It is in. For example, assuming that the daytime power demand in summer is 100, that at dawn is 30 or less. On the other hand, from the viewpoint of the power supply source, the ratio of nuclear power generation or large-scale thermal power generation, whose output fluctuation is not desirable, tends to increase, so that the necessity for equipment for storing electric power is increasing.

[0003] At present, power storage is performed by pumped-storage power generation, but due to its limited location, it is said that new power storage technologies, especially technically and economically, are highly feasible. Secondary batteries for power storage are being actively researched. Among them, a redox flow type battery has attracted particular attention.

FIG. 1 is a schematic diagram of an all-vanadium redox flow battery disclosed in Japanese Patent Publication No. 2724817.

Referring to FIG. 1, an all-vanadium redox flow battery 1 includes a battery cell 2, a negative electrode solution tank 3 and a positive electrode solution tank 4. The inside of the battery reaction cell 2 is partitioned by a diaphragm 5 made of, for example, an ion exchange membrane, and one side constitutes a negative electrode cell 2a and the other side constitutes a positive electrode cell 2b.

[0006] In the positive electrode cell 2b, a positive electrode 6 is provided as an electrode.
And the negative electrode 7 is stored in the negative electrode cell 2a. The positive electrode cell 2b and the positive electrode solution tank 4 are connected by a positive electrode solution circulation line 6, and the negative electrode cell 2a and the negative electrode solution tank 3 are connected.
Are connected by a negative electrode solution circulation line 9.

[0007] A pump 10 is provided in the positive electrode liquid circulation line 6, and a pump 11 is provided in the negative electrode liquid circulation line 9. A positive electrode electrolyte containing V ⁵⁺ / V ⁴⁺ is stored in the positive electrode liquid tank 4.
A negative electrode electrolyte containing V ²⁺ / V ³⁺ is stored therein. These ions are respectively dissolved in the aqueous sulfuric acid solution.

In the all-vanadium redox flow battery, the V stored in the negative electrode liquid tank 3 is charged during charging.
A sulfuric acid aqueous solution containing 2 ⁺ / V ³⁺ is sent to the negative electrode cell 2 a by the pump 11, emits electrons to an external circuit at the negative electrode 7, oxidizes V ²⁺ to V ³⁺ , Collected. On the other hand, the sulfuric acid aqueous solution containing V ⁵⁺ / V ⁴⁺ ions stored in the positive electrode
b, the positive electrode 6 receives electrons from an external circuit, and V ⁵⁺ is reduced to V ⁴⁺ and collected in the positive electrode solution tank 4. In such an all-vanadium redox flow battery, the charge and discharge reactions in the positive electrode 6 and the negative electrode 7 are as follows:
As shown in FIG.

[0009]

The electrochemical reaction of an all-vanadium redox flow battery is shown above.

However, there is a problem that the balance of the electrolytic solution is lost while repeating the charge / discharge operation. The following two cases can be considered as cases where the balance of the electrolytic solution is lost.

First, when the battery is completely discharged, the positive electrode is placed in FIG.
In this case, pentavalent remains. Usually this 5
Since the tetravalent is reduced by the amount of the remaining valence, the capacity is reduced by the amount of pentavalent. The only way to recover is to add tetravalent to the remaining pentavalent or chemically change pentavalent to tetravalent.

Second, when the battery is completely discharged, the negative electrode
In this case, divalent remains as shown in FIG.

When the balance of the electrolytic solution is lost and the absolute amount of the oxidation-reduction pair (V ⁴⁺ / V ³⁺ or V ⁵⁺ / V ²⁺ ) is reduced, the amount of stored power of the battery, ie, the amount of stored battery, that is, the charge / discharge operation is repeated. The battery capacity will decrease. In addition, the internal resistance of the battery increases, and the charge / discharge efficiency tends to decrease.

In order to regenerate the electrolytic solution, it is necessary to add the electrolytic solution in an amount corresponding to the shortage or to provide a separate electrolytic liquid regenerating device. Adding a large amount of the electrolytic solution is a problem in terms of cost, and when a regenerating device for the electrolytic solution is provided, there is a problem that the device becomes complicated.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and does not require the addition of a large amount of electrolyte and does not require a complicated electrolyte regenerating apparatus. An object of the present invention is to provide a method for regenerating a liquid.

[0016]

The invention according to claim 1 is
V ⁵⁺ / V ⁴⁺ positive electrode electrolyte containing ions and V ²⁺ / V ³⁺ ions
Vanadium consisting of a redox pair of a negative electrode electrolyte containing nitrogen
The present invention relates to a method for regenerating a redox flow battery electrolyte. The person
The method uses a positive electrode electrolyte in an unbalanced discharge state.
Adding vanadium trivalent in an amount represented by the following formula
Is provided. The amount of trivalent vanadium added = ([[V ⁵⁺ ion concentration above]
Degree]-[V ²⁺ ion concentration]) × 1/2 As the added vanadium trivalent, the positive electrode electrolyte at the time of discharge
Use the same composition as

According to the present invention, the amount of imbalance
([V ⁵⁺ ion concentration] − [V ²⁺ ion concentration
Degree]) , and by adding a half amount of vanadium trivalent substantially, the surplus vanadium pentavalent is used to make V
By causing ⁵⁺ + V ³⁺ → reaction 2V ^4+, it is possible to reduce the amount of electrolyte solution added. Also, the added vanadium trivalent
The same as the composition of the cathode electrolyte at the time of discharge
Therefore, no side reaction occurs. The density adjustment
No need. Because the reaction occurs 100% accurately,
/ 2, and it is necessary to add sulfuric acid etc. for concentration adjustment.
No need.

According to a second aspect of the present invention, there is provided a semiconductor device comprising: a V ⁵⁺ / V ⁴⁺ ion;
And B2 ⁺ / ^{V3 +} ions
Vanadium redox flow composed of redox pairs
The present invention relates to a method for regenerating a battery electrolyte. Unbalanced discharge
The amount of vanadium represented by the following formula
It is characterized by adding tetravalent chromium. Vanadium tetravalent amount to be added = ([V ²⁺ ion concentration
Degree]-[ ^{V5 +} ion concentration]) × 1/2

According to the present invention, the amount of imbalance
([ Concentration of the above V ²⁺ ion] − [concentration of the above V ⁵⁺ ion
Degree]) , by adding substantially half the amount of vanadium tetravalent, the surplus vanadium divalent is used to make V
By causing the reaction of 2 ⁺⁺ V ⁴⁺ → 2V ^3+, the amount of the added electrolyte can be reduced.

According to a third aspect of the present invention, there is provided a semiconductor device comprising: a V ⁵⁺ / V ⁴⁺ ion;
And B2 ⁺ / ^{V3 +} ions
Vanadium redox flow composed of redox pairs
The present invention relates to a method for regenerating a battery electrolyte. Unbalanced discharge
The amount of vanadium represented by the following formula
Pentavalent. The amount of pentavalent vanadium added = ([[V ²⁺ ion concentration above]
Degree]-[ ^{V5 +} ion concentration]) × ^{上 記}

By adding pentavalent vanadium, V²⁺+ V
²⁺+ V⁵⁺→ V²⁺+ V⁴⁺+ V³⁺→ 3V ³⁺Reacts with and adds
The amount of electrolyte can be further reduced.

The method for regenerating an electrolyte of a vanadium redox flow battery according to a fourth aspect is characterized in that O ₂ is added to the negative electrode electrolyte in an unbalanced discharge state.

Since vanadium divalent is oxidized by oxygen and returns to vanadium trivalent, the electrolytic solution can be regenerated by putting oxygen gas into the negative electrode tank without using a special regenerator.

A fifth aspect of the present invention is directed to a method for regenerating an electrolyte of a vanadium redox flow battery, wherein air is added to the negative electrode electrolyte in an unbalanced discharge state.

Since the air contains about 20% of oxygen, the oxygen is used to regenerate the negative electrode electrolyte. Therefore, a special device, an electrolytic solution, and oxygen gas are not required.

[0026] In the reproducing method of all vanadium redox flow battery electrolyte according to claim 6, as the O ₂ gas, using O ₂ gas can be in the positive electrode at the time of reproduction of the negative electrode electrolyte.

[0027] In the positive electrode, instead of the V ⁴⁺ → V ^5+, as a side _{reaction, 1 / 2H 2 O → 1} / 4O 2 ↑ + H + + e - reaction occurs in. The oxygen generated at this time is supplied to the electrolyte in the negative electrode tank to regenerate the electrolyte. This allows a complete sealing of the device. Another advantage is that manual operation is not required.

[0028]

In the method for regenerating the electrolyte solution of an all-vanadium redox flow battery according to claim 7 , the same vanadium tetravalent as the composition of the cathode electrolyte solution at the time of discharge is used. According to the present invention, since no impurities enter, the liquid is almost the same as the original liquid, and the liquid is more stable.

In the method for regenerating the electrolyte solution of the all-vanadium redox flow battery according to claim 8 , the vanadium pentavalent having the same composition as the cathode electrolyte at the time of charging is used. According to the present invention, since no impurities enter, the liquid is almost the same as the original liquid, and the liquid is more stable.

[0031]

Embodiments of the present invention will be described below.

The electrochemical reaction of an all vanadium redox flow battery using vanadium and sulfuric acid is shown as follows. The positive electrode side and the negative electrode side are separated by a diaphragm.

[0033]

Embedded image

When the balance of the electrolytic solution is lost, the following regeneration is performed.

Embodiment 1 The balance of the electrolytic solution was lost, and the positive electrode: vanadium tetravalent 1 mol, vanadium pentavalent 4 mol, negative electrode: vanadium trivalent 2 mol, vanadium divalent 3 mol. 0.5 mol of trivalent vanadium was added to the positive electrode. As a result, vanadium tetravalent became 2 mol and vanadium pentavalent became 3.5 mol, and the concentrations of vanadium tetravalent and vanadium trivalent could be made the same.

The reaction formula is as follows.

[0037]

Embedded image

By adding vanadium trivalent, a special regenerator is not required, and the added electrolyte is vanadium 4
For the added value, only half the amount is required.

Embodiment 2 The balance of the electrolyte solution was lost, and the positive electrode: vanadium tetravalent 2 mol, vanadium pentavalent 3 mol, negative electrode: vanadium trivalent 1 mol, vanadium divalent 4 mol. When 0.5 mol of vanadium tetravalent was added to the negative electrode, vanadium trivalent was 2 mol.
The mole and vanadium divalent became 3.5 mole, and the concentrations of vanadium trivalent and vanadium tetravalent could be made the same.

The reaction formula is as follows.

[0041]

Embedded image

Embodiment 3 The balance of the electrolyte solution was lost, and the positive electrode: vanadium tetravalent 2 mol, vanadium pentavalent 3 mol, negative electrode: vanadium trivalent 1 mol, vanadium divalent 4 mol. When 0.33 mol of pentavalent vanadium was added to the negative electrode, the trivalent vanadium became 2 mol and the divalent vanadium became 3.33 mol, and the concentrations of trivalent vanadium and tetravalent vanadium could be made the same.

The reaction formula is as follows.

[0044]

Embedded image

By adding vanadium pentavalent, a special regenerator is not required, and the added electrolyte is vanadium 3
One third is sufficient for adding the price.

[0046]Embodiment 4 The balance of the electrolyte is lost, and the positive electrode: Vanadium tetravalent
, Vanadium pentavalent 3 mol, negative electrode: vanadium trivalent 1 mol
And vanadium divalent 4 mol. O on the negative electrode _Two To
When 0.25 mol was added, vanadium trivalent was 2 mol,
Vanadium divalent becomes 3 moles, vanadium trivalent and vana
The concentration of tetravalent dymium could be the same.

The reaction formula is as follows.

[0048]

Embedded image

Since vanadium divalent is oxidized by oxygen and returns to vanadium trivalent, no special regenerating device or the like is required by putting oxygen gas into the negative electrode tank.

Embodiment 5 The balance of the electrolyte solution was lost, and the positive electrode: vanadium tetravalent 5 mol, vanadium pentavalent 0 mol, negative electrode: vanadium trivalent 4 mol, vanadium divalent 1 mol. When air was added to the negative electrode, vanadium trivalent became 5 mol and vanadium divalent became 0 mol, and the concentrations of vanadium trivalent and vanadium tetravalent could be made the same.

Since air contains about 20% of oxygen, regeneration is performed using the oxygen, so that a special device, an electrolytic solution, an oxygen gas and the like are not required.

Embodiment 6 A charge / discharge test was performed by attaching a communication tube to the upper part (gas phase part) of the positive and negative electrode tanks. When the charge / discharge test was performed with the communication tube closed, the battery capacity decreased by 3% in 100 cycles. However, when the communication tube was opened and the charge / discharge test was performed again, the battery capacity decreased by 1%, and the battery capacity decreased by 2%. The electrolyte could be regenerated.

Side reactions at the positive electrode (instead of V ⁴⁺ → V ⁵⁺ ,
Oxygen generated by ＨH ₂ O → １ ／ O ₂ ↑ + H ⁺ + e ⁻ ) is supplied to the electrolyte in the negative electrode tank to regenerate the negative electrode electrolyte.

Embodiment 7 By using the same V ³⁺ used in the first embodiment as the electrolyte composition at the time of discharging the negative electrode (the same concentration of vanadium sulfate (trivalent) and sulfuric acid), No other ingredients enter. As a result, a more stable electrolytic solution can be obtained.

Eighth Embodiment As V ⁴⁺ used in the second embodiment, the same one as the electrolyte composition at the time of complete discharge of the positive electrode (the same concentration of vanadium sulfate (tetravalent) and sulfuric acid) is used. Thereby, since other components do not enter, a more stable electrolytic solution is obtained.

Ninth Embodiment As V ⁵⁺ used in the third embodiment, the same V ⁵⁺ as the electrolyte composition at the time of full charge of the positive electrode (the same concentration of vanadium sulfate (pentavalent) and sulfuric acid) is used. Thereby, other components do not enter and a more stable electrolytic solution is obtained.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram of a conventional all-vanadium redox flow battery.

FIG. 2 is a reaction diagram showing the operating principle of an all-vanadium redox flow battery.

FIG. 3 is a diagram for explaining that the balance of an electrolytic solution is lost.

FIG. 4 is another diagram illustrating that the balance of the electrolytic solution is lost.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 vanadium redox battery 2 battery cell 3 negative electrode liquid tank 4 positive electrode liquid tank 5 diaphragm 6 positive electrode 7 negative electrode 2 a negative electrode cell 2 b positive electrode cell

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Nobuyuki Tokuda 3-2-22-2 Nakanoshima, Kita-ku, Osaka-shi, Osaka Inside Kansai Electric Power Company (56) References JP-A-3-64864 (JP, A) JP-A JP-A-4-149965 (JP, A) JP-A-5-303973 (JP, A) JP-A-9-283169 (JP, A) International publication 89/5536 (WO, A1) (58) Fields investigated (Int. Cl. ⁶ , DB name) H01M 8/00-8/24

Claims (8)

(57) [Claims] 1. A cathode electrolyte containing V ⁵⁺ / V ⁴⁺ ions and V
^{From the} redox pair of the negative electrode electrolyte containing 2 ⁺ / ^{V3 +} ions.
For regenerating electrolyte solution of all vanadium redox flow batteries
In the positive electrode electrolyte in an unbalanced discharge state,
A step of adding an amount of vanadium trivalent represented by the formula: the amount of vanadium trivalent to be added = ([[ concentration of the V ⁵⁺ ion]
Degree]-[ concentration of V ²⁺ ion]) × 1/2 As the added vanadium trivalent, the positive electrode electrolyte at the time of discharge
A method for regenerating an all-vanadium redox flow battery electrolyte , characterized by using the same composition as in (1) . 2. A cathode electrolyte containing V ⁵⁺ / V ⁴⁺ ions and V
^{From the} redox pair of the negative electrode electrolyte containing 2 ⁺ / ^{V3 +} ions.
For regenerating electrolyte solution of all vanadium redox flow batteries
In the negative electrode electrolyte in an unbalanced discharge state,
Characterized in that the amount of vanadium tetravalent represented by the formula is added.
A method for regenerating an electrolyte solution for an all-vanadium redox flow battery. Vanadium tetravalent amount to be added = ([V ²⁺ ion concentration
Degree]-[ Concentration of the ^{V5 +} ion]) × 1/2 3. A cathode electrolyte containing V ⁵⁺ / V ⁴⁺ ions and V
^{From the} redox pair of the negative electrode electrolyte containing 2 ⁺ / ^{V3 +} ions.
For regenerating electrolyte solution of all vanadium redox flow batteries
In the negative electrode electrolyte in an unbalanced discharge state,
Adding vanadium pentavalent in an amount represented by the formula
A method for regenerating an electrolyte solution for an all-vanadium redox flow battery. Vanadium pentavalent amount to be added = ([V ²⁺ ion concentration
Degree]-[ Concentration of ^{V5 +} ion]) × １ ／ 4. The method according to claim 1, wherein O ₂ is added to the negative electrode electrolyte in an unbalanced discharge state for regeneration.
A method for regenerating the electrolyte solution for all vanadium redox flow batteries. 5. The method according to claim 1, wherein air is added to the negative electrode electrolyte in an unbalanced discharge state for regeneration.
A method for regenerating the electrolyte solution for all vanadium redox flow batteries. As claimed in claim 6, wherein said O _2, characterized by using an O ₂ gas made of the positive electrode during reproduction of the negative electrode electrolyte,
A method for regenerating the electrolyte of the all-vanadium redox flow battery according to claim 4. 7. The method for regenerating an all-vanadium redox flow battery electrolyte according to claim 2, wherein the same vanadium tetravalent as the composition of the cathode electrolyte during discharge is used. 8. The method for regenerating an all-vanadium redox flow battery electrolyte according to claim 3, wherein the vanadium pentavalent uses the same composition as the composition of the cathode electrolyte at the time of full charge.