JP7216080B2 - Redox flow battery and its operation method - Google Patents

Description

The present invention relates to a redox flow battery in which a positive electrode electrolyte and a negative electrode electrolyte contain ions of the same metal element whose valence changes, and a method of operating the redox flow battery.

Redox flow batteries are used for load leveling of electric power and countermeasures against momentary shutdown, and are attracting attention as new electric power storage batteries. In particular, redox flow batteries using vanadium salt as an active material are known , see Patent Document 1).

The principle of operation of the redox flow battery will be explained based on FIG.
The redox flow battery 100 includes a battery cell 110 separated into a positive electrode cell 100A and a negative electrode cell 100B by a diaphragm 101 made of an ion exchange membrane, electrolyte tanks 104A and 104B for storing electrolyte, and electrolyte tanks 104A and 104B. circulation pipes 106A and 106B for circulating and supplying the electrolyte to the battery cells 110; and circulation pumps 105A and 105B connected to the circulation pipes 106A and 106B for circulating the electrolyte.

A positive electrode 102 is incorporated in the positive electrode cell 100A, and a negative electrode 103 is incorporated in the negative electrode cell 100B.
A positive electrode electrolyte tank 104A that stores a positive electrode electrolyte is connected to the positive electrode cell 100A via a positive electrode electrolyte circulation pipe 106A, and a negative electrode electrolyte tank 104B that stores a negative electrode electrolyte is connected to the negative electrode cell 100B. They are connected via a negative electrode electrolyte circulation pipe 106B. Circulation pipes 106A and 106B are provided with circulation pumps 105A and 105B, respectively. circulated.

An aqueous solution of ions whose valence changes, such as vanadium ions, is used as an active material in each electrode electrolyte. Charging and discharging are performed along with the reaction.

For example, when an electrolytic solution containing vanadium ions is used, reactions that occur during charging and discharging at the positive and negative electrodes in the cell are as follows. In fact, it is presumed that V ⁴⁺ exists as VO ²⁺ and V ⁵⁺ exists as VO ²⁺ , and each exists in a hydrated state or in a state in which a sulfate group is coordinated. presumed to be
Positive electrode: V ⁴⁺ → V ⁵⁺ + e ^- (charge) V ⁴⁺ ← V ⁵⁺ + e ^- (discharge)
Negative electrode: V ³⁺ + e ^- → V ²⁺ (charge) V ³⁺ + e ^- ← V ²⁺ (discharge)

Hydrogen ions (H ⁺ ) generated at the positive electrode during charging move through the diaphragm 101 to the negative electrode side, and the electrical neutrality of the electrolyte is maintained. Electric power supplied from a power generation unit (for example, a power plant) is stored in an electrolyte tank as valence changes of vanadium ions with different valences.
On the other hand, during discharging, the stored power can be extracted by a reaction opposite to that during charging, and supplied to a load (such as a consumer).

In the redox flow battery, the state of charge (SOC) of the electrolyte is determined by the ratio of ionic valences in the electrolyte. For example, in the case of a vanadium-based redox flow battery, the ratio of V ⁵⁺ in the vanadium ions (V ⁴⁺ /V ⁵⁺ ) in the positive electrode electrolyte in the positive electrode electrolyte, and the vanadium ion in the negative electrode electrolyte in the negative electrode electrolyte It is expressed by the ratio of V ²⁺ in (V ²⁺ /V ³⁺ ). In the battery reaction during charging, V ⁴⁺ is oxidized to V ⁵⁺ at the positive electrode in the battery cell, and V ³⁺ is reduced to V ²⁺ at the negative electrode. The battery reaction during discharging is the opposite reaction to that during charging.

In vanadium redox flow batteries, the full charge voltage (charge completion voltage, charge end voltage) and discharge end voltage are set in advance from the viewpoint of deterioration suppression and charging efficiency. Charging and discharging are performed within a chargeable/dischargeable range from the end of discharge (for example, state of charge: 20%) to full charge (for example, state of charge: 80%). Here, the full charge voltage is a voltage set to stop charging from the power system, and the end-of-discharge voltage is a voltage set to stop discharge to the power system.

JP-A-62-186473 JP 2006-147375 A JP-A-11-204124 JP-A-2001-43884 U.S. Patent Application Publication No. 2014/0193673

Since the active material in the electrolyte of the vanadium-based redox flow battery is a single-element system, there is an advantage that even if the positive electrode electrolyte and the negative electrode electrolyte are mixed, they can be regenerated by charging. However, even in a redox flow battery, when charging and discharging are repeated, various ions and solvents in the electrolytic solution move through the diaphragm, causing an increase or decrease in the amount of the electrolytic solution in the positive electrode and the negative electrode. As a result, the balance between the active material ions of the positive electrode electrolyte and the negative electrode electrolyte is lost, and the battery capacity is determined according to the cell in a low state of charge, resulting in a decrease in battery capacity.

As a method of rebalancing to eliminate such imbalance of active material ions, for example, as disclosed in Patent Documents 2 to 4, the positive electrode electrolyte tank and the negative electrode electrolyte tank are communicated by a communication pipe, A configuration has been proposed in which a valve is provided in this communicating pipe, and the valve is opened when the amount of electrolytic solution in the tank decreases to mix the positive electrode electrolyte and the negative electrode electrolyte through the communicating pipe.

However, in the case of mixing the positive electrode electrolyte and the negative electrode electrolyte in this way, facilities such as a communication pipe and a pump are required. In particular, when there are many tanks, communication pipes and pumps are required for the number of pairs.

Further, when the positive electrode electrolyte and the negative electrode electrolyte are mixed through the communicating pipe, it takes a long time to sufficiently mix the positive electrode electrolyte and the negative electrode electrolyte, depending on the diameter of the communicating pipe and the performance of the pump. It takes time. The time required for mixing the positive electrode electrolyte and the negative electrode electrolyte is the time during which the redox flow battery cannot be used, and the shorter the time, the better.

In view of the current situation, the present invention eliminates the need for facilities such as communication pipes and pumps when mixing the positive electrode electrolyte and the negative electrode electrolyte for rebalancing, and rapidly mixes the positive electrode electrolyte and the negative electrode electrolyte. An object of the present invention is to provide a redox flow battery capable of rebalancing by mixing with a liquid.

The present invention was invented to solve the problems in the prior art as described above, and the present invention includes, for example, the following aspects.

[1] A redox flow battery in which a positive electrode electrolyte and a negative electrode electrolyte contain ions of the same metal element whose valence changes, wherein the electrolyte is stored in an electrolyte tank. The electrolyte bath is separated by a partition wall into a positive electrode electrolyte bath connected to the positive electrode cell of the battery cell by a circulation pipe and a negative electrode electrolyte bath connected to the negative electrode cell of the battery cell by a circulation pipe, A redox flow battery in which the partition wall is configured to be openable and closable.

[2] The redox flow battery according to item [1], wherein the partition includes an opening/closing portion, and the opening/closing portion is configured to be movable up and down.

[3] The redox flow battery according to item [2], wherein the opening/closing portion is configured to be rotatable.

[4] The redox flow battery according to item [2], wherein the partition has a hole, and the hole is opened and closed by moving up and down the opening and closing section.

[5] The redox flow battery according to item [1], wherein the partition includes an opening/closing portion, and the opening/closing portion is horizontally openable and closable.

[6] The partition includes an opening and closing part,
The redox flow battery according to item [1], wherein the opening/closing part is configured to be rotatable about a horizontal axis.

[7] The redox flow battery according to any one of items [1] to [6], which includes a stirring device in the electrolyte bath.

[8] A battery cell having a positive electrode cell connected to the positive electrode electrolyte bath and a negative electrode cell connected to the negative electrode electrolyte bath;
The redox flow battery according to any one of items [1] to [7], further comprising an electrolytic solution stored in the electrolytic solution tank and supplied to the positive electrode cell and the negative electrode cell.

[9] The redox flow battery according to item [8], wherein the electrolytic solution is an aqueous solution containing vanadium ions.

[10] The method of operating a redox flow battery according to any one of [1] to [9], wherein the partition is closed when the redox flow battery is charged and discharged. and a method of operating a redox flow battery in which the partition wall is opened when the redox flow battery is rebalanced.

According to the present invention, by providing an openable and closable partition in the electrolytic solution tank in which the electrolytic solution is stored, when the redox flow battery is charged and discharged, the partition is closed and the positive electrode electrolytic solution tank and the negative electrode electrolytic solution tank are closed. On the other hand, when performing rebalancing, the partition can be opened to quickly mix the electrolyte.

FIG. 1 is a schematic diagram illustrating the configuration of the redox flow battery in this example. FIG. 2 is a schematic diagram showing an example of an electrolytic solution tank of the redox flow battery shown in FIG. FIG. 3 is a schematic diagram showing a modification of the partition wall of the electrolyte bath. FIG. 4 is a schematic diagram showing another modification of the partition wall of the electrolyte bath. FIG. 5 is a schematic diagram showing still another modification of the partition wall of the electrolyte bath. FIG. 6 is a schematic diagram for explaining a conventional redox flow battery.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments (examples) of the present invention will be described in more detail with reference to the drawings. In the drawings used in the following description, there are cases where characteristic portions are enlarged for convenience in order to make it easier to understand the features of the present invention, and the dimensional ratios of each component may differ from the actual ones. be. In addition, the materials, dimensions, etc. exemplified in the following description are examples, and the present invention is not limited to them.

FIG. 1 is a schematic diagram illustrating the configuration of the redox flow battery in this example.
As shown in FIG. 1, the redox flow battery 10 includes a battery cell 20 separated into a positive electrode cell 10A and a negative electrode cell 10B by a diaphragm 11 made of an ion exchange membrane, an electrolytic solution tank 30 storing an electrolytic solution 31, Circulation pipes 16A and 16B for circulating and supplying the electrolyte 31 from the electrolyte bath 30 to the battery cells 20, and circulation pumps 15A and 15B connected to the circulation pipes 16A and 16B for circulating the electrolyte 31 are provided. A positive electrode 12 is contained in the positive electrode cell 10A, and a negative electrode 13 is contained in the negative electrode cell 10B.

A known configuration can be adopted as the battery cell 20 in the present invention.

The electrolyte bath 30 is separated by a partition wall 32 into a positive electrode electrolyte bath 34A and a negative electrode electrolyte bath 34B. The positive electrode electrolyte bath 34A is connected to the positive electrode cell 10A through the positive electrode electrolyte circulation pipe 16A, and the negative electrode electrolyte bath 34B is connected to the negative electrode cell 10B through the negative electrode electrolyte circulation pipe 16B.

The circulation pipes 16A and 16B are provided with circulation pumps 15A and 15B, respectively. It is circulated between the cells 10A and 10B.

The discharge port 16A1 and the suction port 16A2 of the positive electrode electrolyte bath 34A are preferably arranged at positions as far apart as possible in the positive electrode electrolyte bath 34A. Moreover, it is preferable that the discharge port 16B1 and the suction port 16B2 of the negative electrode electrolyte bath 34B are arranged at positions as far apart as possible in the negative electrode electrolyte bath 34B.

In this embodiment, an aqueous solution containing vanadium ions is used as the electrolytic solution 31, but the electrolytic solution is not particularly limited as long as it contains ions of metal elements whose valence changes. Also, the positive electrode electrolyte (the electrolyte 31 supplied from the positive electrode electrolyte tank 34A to the positive electrode cell 10A) and the negative electrode electrolyte (the electrolyte 31 supplied from the negative electrode electrolyte tank 34B to the negative electrode cell 10B) are different. , contain ions of the same metal element. The positive electrode electrolyte and the negative electrode electrolyte need only contain the same element as ions, and do not necessarily have the same ions or compounds. In addition, the positive electrode electrolyte and the negative electrode electrolyte have the same composition from after mixing during rebalancing to before charging.

It should be noted that the electrolytic solution tank 30 is preferably made of an acid-resistant material, or the inside thereof is preferably subjected to an acid-resistant treatment. From the viewpoint of manufacturing cost, it is preferable that the electrolytic solution tank 30 is made of concrete subjected to acid-resistant treatment.

Moreover, it is preferable that the partition wall 32 is formed of an acid-resistant material, or the surface thereof is subjected to an acid-resistant treatment. In addition, as will be described later, since the opening and closing part 32A is provided to open and close the partition wall 32, it is preferable to use a material with high workability, light weight, and high strength. For example, fiber reinforced plastic (FRP) is used. be able to.

In this embodiment, as shown in FIG. 2, the partition wall 32 of the electrolyte bath 30 is partially openable and closable.
In the electrolytic solution bath 30 shown in FIG. 2, the partition wall 32 is provided with an opening/closing portion 32A, and the opening/closing portion 32A is opened and closed by raising and lowering the opening/closing portion 32A by a lifting means (not shown).

When the redox flow battery 10 is charged and discharged, the opening/closing part 32A is lowered and the partition wall 32 is closed. On the other hand, when performing rebalancing, the opening/closing portion 32A is raised to open the partition wall 32 . As a result, the electrolyte stored in the positive electrode electrolyte bath 34A and the electrolyte stored in the negative electrode electrolyte bath 34B are mixed.

Further, in this embodiment, the opening/closing portion 32A is configured to be rotatable about a vertical axis by a rotating means (not shown). With this configuration, by rotating the opening/closing portion 32A, the electrolyte solution 31 in the electrolyte solution tank 30 can be made to flow, and rebalance can be performed more quickly. In this case, it is preferable to raise the opening/closing part 32A to a degree that allows the opening/closing part 32A to be freely rotated so that the opening/closing part 32A is more immersed in the electrolytic solution 31, because the electrolytic solution 31 is easily agitated.

Further, when performing rebalance, the circulation pumps 15A and 15B provided in the circulation pipes 16A and 16B may be operated. As a result, the electrolytic solution 31 remaining in each of the cells 10A and 10B and the circulation pipes 16A and 16B is also mixed, and rebalance can be performed more uniformly. Further, by operating the circulation pumps 15A and 15B, the effect of flowing the electrolytic solution 31 in the electrolytic solution tank 30 can also be obtained.

For example, a stirring device using an impeller, a pump, or the like may be provided in the electrolyte bath 30 to stir the electrolyte 31 .

FIG. 3 is a schematic diagram showing a modification of the partition wall of the electrolyte bath.
As shown in FIG. 3, the opening/closing portion 32A is configured to open and close in the horizontal direction, and is operated by a moving means (not shown).

In this configuration, the electrolyte 31 in the electrolyte bath 30 can be caused to flow by operating the circulation pumps 15A and 15B provided in the circulation pipes 16A and 16B as described above. can. Alternatively, a stirring device using an impeller, a pump, or the like, for example, may be provided in the electrolyte bath 30 .

FIG. 4 is a schematic diagram showing another modification of the partition wall of the electrolyte bath.
As shown in FIG. 4, a hole 32B is provided in a part of the partition wall 32, and the opening/closing portion 32A can be opened/closed by raising and lowering the opening/closing portion 32A by means of an elevating means (not shown). .

In this configuration, the electrolyte 31 in the electrolyte bath 30 can be caused to flow by operating the circulation pumps 15A and 15B provided in the circulation pipes 16A and 16B as described above. can. Alternatively, a stirring device using an impeller, a pump, or the like, for example, may be provided in the electrolyte bath 30 .

FIG. 5 is a schematic diagram showing still another modification of the partition wall of the electrolyte bath.
As shown in FIG. 5, the partition wall 32 as a whole serves as an opening/closing portion 32A, and is configured to be rotatable about a horizontal axis by a rotating means (not shown).

With this configuration, by rotating the opening/closing part 32A, the electrolytic solution 31 in the electrolytic solution tank 30 can be made to flow and the electrolytic solution 31 can be stirred.
In the example shown in FIG. 5, the entire partition 32 serves as the opening/closing portion 32A, but a portion of the partition 32 may serve as the opening/closing portion 32A.

Further, as described above, the electrolyte solution 31 in the electrolyte solution bath 30 may be caused to flow by operating the circulation pumps 15A and 15B provided in the circulation pipes 16A and 16B. Further, a stirring device using an impeller, a pump, or the like, for example, may be provided in the electrolyte bath 30 .

Although the preferred embodiment of the present invention has been described above, the present invention is not limited to this. In the above embodiment, a configuration in which a part of the partition wall can be opened and closed has been described, but the entire partition wall can be opened and closed. Various modifications are possible without departing from the object of the present invention.

10 Redox flow battery 10A Positive electrode cell 10B Negative electrode cell 11 Diaphragm 12 Positive electrode 13 Negative electrode 15A Circulation pump 15B Circulation pump 16A Positive electrode electrolyte circulation pipe 16B Negative electrode electrolyte circulation pipe 16A1 Outlet 16A2 Suction port 16B1 Outlet 16B2 Suction port 20 Battery Cell 30 Electrolyte bath 31 Electrolyte 32 Separation wall 32A Open/close part 32B Hole 34A Positive electrode electrolyte bath 34B Negative electrode electrolyte bath 100 Redox flow battery 100A Positive electrode cell 100B Negative electrode cell 101 Diaphragm 102 Positive electrode 103 Negative electrode 104A Positive electrode electrolyte tank 104B Negative electrode Electrolyte tank 105A Circulation pump 105B Circulation pump 106A Positive electrode electrolyte circulation pipe 106B Negative electrode electrolyte circulation pipe 110 Battery cell

Claims (10)

A redox flow battery in which an electrolyte solution containing ions of the same metal element whose valence changes is used for the positive electrode electrolyte and the negative electrode electrolyte,
An electrolytic solution tank in which the electrolytic solution is stored,
The electrolytic solution tank is separated by a partition into a positive electrode electrolytic solution tank connected to the positive electrode cell of the battery cell by a circulation pipe and a negative electrode electrolytic solution tank connected to the negative electrode cell of the battery cell by a circulation pipe,
A redox flow battery in which the partition wall is configured to be openable and closable. the partition comprises an opening and closing part,
The redox flow battery according to claim 1, wherein the opening/closing part is configured to be movable up and down. The redox flow battery according to claim 2, wherein the opening/closing part is configured to be rotatable around a vertical axis. the partition comprises a hole;
The redox flow battery according to claim 2, wherein the hole is opened and closed by moving up and down the opening and closing portion. the partition comprises an opening and closing part,
The redox flow battery according to claim 1, wherein the opening/closing portion is configured to be horizontally openable and closable. the partition comprises an opening and closing part,
The redox flow battery according to claim 1, wherein the opening/closing part is configured to be rotatable around a horizontal axis. The redox flow battery according to any one of claims 1 to 6, wherein a stirring device is provided in said electrolyte bath. a battery cell having a positive electrode cell connected to the positive electrode electrolyte bath and a negative electrode cell connected to the negative electrode electrolyte bath;
an electrolytic solution stored in the electrolytic solution tank and supplied to the positive electrode cell and the negative electrode cell,
The redox flow battery according to any one of claims 1 to 7, wherein the electrolyte contains ions of metal atoms with varying valences. The redox flow battery according to claim 8, wherein the electrolytic solution is an aqueous solution containing vanadium ions. A method for operating the redox flow battery according to any one of claims 1 to 9,
When charging and discharging the redox flow battery, the partition is closed and used,
A method of operating a redox flow battery in which the partition wall is opened when the redox flow battery is rebalanced.

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