Redox flow battery

Abstract

To provide a redox flow battery capable of cancelling reduction of charge / discharge efficiency or capacity reduction caused by potential imbalance between a first electrode and a second electrode even if a power storage rate range is enlarged.SOLUTION: A redox flow battery comprises: at least one cell in which a first chamber where a first electrode to be a cathode at the time of charging is installed and a second chamber where a second electrode to be an anode at the time of charging is installed are separated by a partition film; a first circulation device including a first tank in which a first electrolyte is stored, a first supply path connecting the first tank with the first chamber and a first collection path connecting the first chamber with the first tank; a second circulation device including a second tank in which a second electrolyte is stored, a second supply path connecting the second tank with the second chamber and a second collection path connecting the second chamber with the second tank; and an adjustment circuit provided to supply a gas contained in the first tank or the first collection path to the second collection path.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a redox flow battery.

Background Art

[0002] Patent Document 1 discloses a redox flow battery. The redox flow battery includes a cell, a first tank, a first circulation device, a second tank, and a second circulation device. The cell has a first chamber containing a first electrode, a second chamber containing a second electrode, and a diaphragm partitioning the first chamber and the second chamber. A first electrolytic solution is stored in the first tank, and the first electrolytic solution circulates between the first tank and the first chamber by the first circulation device. Similarly, a second electrolytic solution is stored in the second tank, and the second electrolytic solution circulates between the second tank and the second chamber by the second circulation device.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the conventional configuration shown in Patent Document 1, when the power storage rate range of the redox flow battery is expanded, hydrogen and oxygen are generated by electrolysis, so there is a risk of a decrease in charge / discharge efficiency and a decrease in capacity due to a deviation in the potential balance between the first electrode and the second electrode.

[0005]

Means for Solving the Problems

[0006] To achieve the above object, the redox flow battery according to the present disclosure includes: At least one cell in which a first chamber where a first electrode serving as an anode during charging is installed and a second chamber where a second electrode serving as a cathode during charging is installed are partitioned by a diaphragm; A first tank for storing a first electrolytic solution; A first circulation device including a first supply path connecting the first tank and the first chamber and a first recovery path connecting the first chamber and the first tank; A second tank for storing a second electrolytic solution; A second circulation device including a second supply path connecting the second tank and the second chamber and a second recovery path connecting the second chamber and the second tank; An adjustment path provided to supply gas contained in the first tank or the first recovery path to the second recovery path; Comprising 、 The adjustment path communicates with the gas phase in the first recovery path and the liquid phase in the second recovery path. thereof.

Advantages of the Invention

[0007] According to the redox flow battery of the present disclosure, by expanding the power storage range of the redox flow battery, the gas containing oxygen generated from the first electrode is supplied to the second recovery path. As a result, the oxygen contained in the gas is mixed with the second electrolytic solution in the second recovery path and supplied to the cell (second chamber). Then, in the cell (second chamber), the oxygen contained in the gas mixed with the second electrolytic solution reacts with the active material contained in the second electrolytic solution, thereby performing forced discharge, eliminating the deviation in the potential balance between the first electrode and the second electrode, and also eliminating the decrease in charge / discharge efficiency and the decrease in capacity.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Mode for Carrying Out the Invention

[0009] Hereinafter, a redox flow battery according to an embodiment will be described with reference to the accompanying drawings. However, the dimensions, materials, shapes, relative arrangements, etc. of the components described as embodiments or shown in the drawings are not intended to limit the scope of the present invention, but are merely illustrative examples.

[0010] [Embodiment 1] <Configuration of Redox Flow Battery 1A> FIG. 1 is a schematic diagram showing the configuration of a redox flow battery 1A according to Embodiment 1. As shown in FIG. 1, the redox flow battery 1A according to Embodiment 1 includes a cell 2, a first tank 3, a first circulation device 4, a second tank 5, a second circulation device 6, and an adjustment path 7A.

[0011] Cell 2 has a first chamber 23 and a second chamber 25 separated by a diaphragm 21. A first electrode 24 is installed in the first chamber 23, and a second electrode 26 is installed in the second chamber 25. The first electrode 24 and the second electrode 26 are each electrically connected to an AC-DC converter 100. The AC-DC converter 100 is electrically connected to an AC power supply 200 and a load 300 respectively. In addition, when a DC power supply is used instead of the AC power supply 200 and the load 300 operates with a DC current, the AC-DC converter 100 is not required. The first electrode 24 is a positive electrode, which becomes an anode into which current flows from the AC-DC converter 100 during charging and a cathode from which current flows out to the AC-DC converter 100 during discharging. The second electrode 26 is a negative electrode, which becomes a cathode from which current flows out to the AC-DC converter 100 during charging and an anode into which current flows from the AC-DC converter 100 during discharging. Only one cell 2 is shown in FIG. 1, but the redox flow battery is not limited to a redox flow battery having only one cell 2, and may be a redox flow battery including a cell stack in which two or more cells 2 are stacked.

[0012] The first tank 3 is a sealed tank in which a first electrolyte ES1 containing an active material is stored. The first electrolyte ES1 is a positive electrode electrolyte, and the first tank 3 constitutes a positive electrode electrolyte tank. The first electrolyte ES1 is an aqueous solution in which an active material is dissolved in an aqueous solution containing a supporting electrolyte. For example, an acidic aqueous solution in which sulfuric acid is dissolved in an aqueous solution containing a supporting electrolyte is used, and vanadium ions (VO2 + (VO 2+ )) are used.

[0013] The first circulation device 4 is a device that circulates the first electrolyte ES1 between the first chamber 23 and the first tank 3, and includes a first supply path 41 connecting the first tank 3 and the first chamber 23, and a first recovery path 43 connecting the first chamber 23 and the first tank 3. The first electrolyte ES1 is circulated by a first pump 42 provided in the first supply path 41. In addition, a first heat exchanger 44 is provided in the first recovery path 43 to maintain the first electrolyte ES1 flowing through the first recovery path 43 within an appropriate temperature range.

[0014] The second tank 5 is a sealed tank in which a second electrolyte ES2 containing an active material is stored. The second electrolyte ES2 is a negative electrode electrolyte, and the second tank 5 constitutes a negative electrode electrolyte tank. The second electrolyte ES2 is obtained by dissolving an active material in an aqueous solution containing a supporting electrolyte. For example, an acidic aqueous solution in which sulfuric acid is dissolved in the supporting electrolyte is used, and vanadium ions (V 2+ (V 3+ )) are used.

[0015] The second circulation device 6 is a device that circulates the second electrolyte ES2 between the second chamber 25 and the second tank 5, and includes a second supply path 61 connecting the second tank 5 and the second chamber 25, and a second recovery path 63 connecting the second chamber 25 and the second tank 5. The second electrolyte ES2 is circulated by a second pump 62 provided in the second supply path 61. Further, a second heat exchanger 64 is provided in the second recovery path 63, and the second electrolyte ES2 flowing through the second recovery path 63 is maintained within an appropriate temperature range.

[0016] As shown in FIG. 2, the inner wall 63a of the second recovery path 63 has a spiral groove 63a1. The spiral groove 63a1 is a groove that describes a spiral in the traveling direction (longitudinal direction), as typified by rifling. The spiral groove 63a1 may be provided over the entire length of the second recovery path 63, or may be provided in a part of the second recovery path 63. For example, it may be provided only up to a portion extending straight from the outlet of the cell 2 so as to impart a swirling component to the second electrolyte ES2 discharged from the cell 2.

[0017] As shown in FIG. 1, the adjustment path 7A is for adjusting the potential imbalance between the first electrode 24 and the second electrode 26 caused by the gas generated by the electrolysis of water. One end of the adjustment path 7A is connected to an upper region in the gravitational direction of the first tank 3, and the other end is connected to the upstream side of the second recovery path 63, preferably the side close to the outlet of the cell 2. The side close to the outlet of the cell 2 is preferred because the path used for gas mixing can be made longer.

[0018] A valve 71 is provided in the adjustment path 7A. The valve 71 opens and closes the adjustment path 7A. When the valve 71 is opened, the gas phase of the first tank 3 and the liquid phase of the second recovery path 63 communicate with each other.

[0019] <Operation of the redox flow battery 1A> By operating the first circulation device 4 and the second circulation device 6, the first electrolyte ES1 is supplied from the first tank 3 to the first chamber 23, and the second electrolyte ES2 is supplied from the second tank 5 to the second chamber 25. As a result, the first chamber 23 is filled with the first electrolyte ES1, the second chamber 25 is filled with the second electrolyte ES2, and the redox flow battery 1A can be charged and discharged.

[0020] When charging the redox flow battery 1A, an alternating current is supplied from the AC power supply 200 to the AC-DC converter 100, and the AC-DC converter 100 converts the alternating current into a direct current. The converted direct current flows to the first electrode 24 (positive electrode). That is, electrons flow from the first electrode (positive electrode) to the second electrode 26 (negative electrode), and at the second electrode 26, the active material in the electrolyte receives the electrons. For example, when vanadium ions (VO 2+ ) are used as the active material of the first electrolyte ES1 and vanadium ions (V 2+ ) are used as the active material of the second electrolyte ES2, taking this as an example, at the first electrode 24 (positive electrode), the reaction represented by the reaction formula "VO 2+ + 2H2O → VO2 + + 2H + " occurs, and at the second electrode 26 (negative electrode), the reaction represented by the reaction formula "V 3+ → V 2+ " occurs.

[0021] When discharging the redox flow battery 1A, reactions occur in each of the first chamber 23 and the second chamber, so that electrons are released from the active material in the electrolyte to the second electrode 26 (negative electrode), and the electrons flow from the second electrode 26 (negative electrode) to the first electrode 24 (positive electrode). For example, when vanadium ions (VO 2+ ) are used as the active material of the first electrolyte ES1 and vanadium ions (V 2+) When [a certain condition] is used as an example, in the first electrode 24 (positive electrode), a reaction represented by the reaction formula "VO2 + +2H + →VO 2+ +2H2O" occurs, and in the second electrode 26 (negative electrode), a reaction represented by the reaction formula "V 2+ →V 3+ " occurs. As a result, electrons are released from the second electrode 26 (negative electrode), and the electrons flow from the second electrode 26 (negative electrode) to the first electrode 24 (positive electrode). Thereby, a current flows from the first electrode 24 (positive electrode) to the AC-DC converter 100.

[0022] When expanding the state-of-charge range when charging the redox flow battery 1A, there is a risk that hydrogen and oxygen may be generated by the electrolysis of water. This hydrogen and oxygen cause a deviation in the potential balance between the first electrode 24 and the second electrode 26, resulting in a decrease in charge-discharge efficiency and a decrease in capacity. And the oxygen generated by the electrolysis of water is recovered into the first tank 3 through the first recovery path 43.

[0023] When the valve 71 is opened in a state where the oxygen generated by the electrolysis of water has accumulated in the first tank 3, the gas phase in the first tank 3 and the liquid phase in the second recovery path 63 communicate with each other. At this time, since the second electrolyte ES2 is flowing in the second recovery path 63, the pressure in the second recovery path 63 becomes lower than the pressure in the adjustment path 7A. Due to this pressure difference, the gas in the adjustment path 7A is drawn into the second recovery path 63 (Bernoulli's theorem). Thereby, the gas in the first tank 3 is supplied to the second recovery path 63 and mixed with the second electrolyte ES2 in the second recovery path 63.

[0024] The second electrolyte ES2 in which gas is mixed in the second recovery path 63 is supplied to the cell 2 (second chamber 25) through the second tank 5 and the second supply path 61. And the oxygen contained in the second electrolyte ES2 in which the gas supplied to the cell 2 is mixed, for example, when vanadium ions (V 2+ ) are used as the active material of the second electrolyte ES2, the oxygen contained in the second electrolyte ES2 reacts with vanadium ions (V 2+ ) (O2+4H + +4V2+ →4V 3+ +2H2O). As a result, V 2+ ions are discharged to V 3+ (forced discharge). This eliminates the potential imbalance between the first electrode 24 and the second electrode 26, and also eliminates the reduction in charge / discharge efficiency and the reduction in capacity.

[0025] <Effect of Redox Flow Battery 1A> According to the redox flow battery 1A according to Embodiment 1, when the valve 71 is opened, the gas phase in the first tank 3 communicates with the liquid phase in the second recovery path 63, the gas in the adjustment path 7A is drawn in, and the gas in the first tank 3 is supplied into the second recovery path 63. Therefore, it is not necessary to separately provide a pump or the like for supplying the gas in the first tank 3 into the second recovery path 63.

[0026] When oxygen generated by the electrolysis of water is supplied to the cell 2 (second chamber 25), forced discharge occurs in the cell (second chamber 25), the potential imbalance between the first electrode 24 and the second electrode is eliminated, and the reduction in charging efficiency and the reduction in capacity are eliminated.

[0027] For example, when vanadium ions (V 2+ ) are used as the active material of the second electrolyte ES2, forced discharge represented by the reaction formula "O2 + 4H + + 4V 2+ → 4V 3+ + 2H2O" is performed, and the potential imbalance between the first electrode 24 and the second electrode 26 is eliminated.

[0028] In addition, since the inner wall 63a of the second recovery path 63 has a spiral groove 63a1, a swirling component is imparted to the second electrolyte ES2 flowing through the second recovery path 63. As a result, the second electrolyte ES2 flowing through the second recovery path 63 swirls in a spiral shape, and the gas supplied from the adjustment path 7A to the second recovery path 63 is effectively mixed with the second electrolyte ES2. As a result, discharge in the cell (second chamber) is performed efficiently.

[0029] [Embodiment 2] FIG. 3 is a schematic diagram showing the configuration of the redox flow battery 1B according to Embodiment 2. The same components as those of the redox flow battery 1A according to Embodiment 1 described above are denoted by the same reference numerals, and the description thereof is omitted.

[0030] As shown in FIG. 3, the redox flow battery 1B according to Embodiment 2 includes a gas sensor 31 that measures the oxygen concentration in the gas phase of the first tank 3. In the redox flow battery 1B according to Embodiment 2, when the oxygen concentration measured by the gas sensor 31 exceeds a predetermined upper threshold value, the valve 71 is opened, and when it falls below the predetermined threshold value, the valve 71 provided in the adjustment path 7B is closed.

[0031] According to the redox flow battery 1B according to Embodiment 2, since the gas in the first tank 3 is supplied to the second recovery path 63 from when the oxygen concentration in the gas phase of the first tank 3 exceeds the upper threshold value until it falls below the lower threshold value, the gas (oxygen) in the first tank 3 can be effectively supplied to the second recovery path 63. Thereby, the reaction in the cell 2 (the second chamber 25) is effectively performed, and the discharge in the cell 2 (the second chamber 25) is efficiently performed.

[0032] [Embodiment 3] FIG. 4 is a schematic diagram showing the configuration of the redox flow battery 1C according to Embodiment 3. The same components as those of the redox flow battery according to Embodiment 1 are denoted by the same reference numerals, and the description thereof is omitted.

[0033] As shown in FIG. 4, in the redox flow battery 1C according to Embodiment 3, the first recovery path 43 has an ascending portion 43a and a descending portion 43b. The ascending portion 43a is a portion extending upward in the direction of gravity. As long as it extends upward in the direction of gravity, it is not limited to extending straight upward, and may be inclined obliquely or may be bent. The descending portion 43b is a portion extending from the upper end 43a1 of the ascending portion 43a toward the first tank 3, and the upper end 43a1 of the ascending portion 43a is at the highest position in the direction of gravity. As long as the upper end 43a1 of the ascending portion 43a is at the highest position in the direction of gravity, the descending portion 43b may be inclined from the upper end 43a1 of the ascending portion 43a toward the first tank 3, or may be bent along the path from the upper end 43a1 of the ascending portion 43a toward the first tank 3. In this way, since the first recovery path 43 has the ascending portion 43a and the descending portion 43b, the gas containing oxygen generated at the first electrode 24 is accumulated at the upper end 43a1 of the ascending portion 43a.

[0034] Further, in the redox flow battery 1C according to Embodiment 3, one end of the adjustment path 7C is connected to the upper end 43a1 of the ascending portion 43a of the first recovery path 43, and the other end is connected to the upstream side of the second recovery path 63, preferably, the side close to the outlet of the cell 2.

[0035] In the redox flow battery 1C according to Embodiment 3, the oxygen generated by the expansion of the charge storage rate range passes through the ascending portion 43a and is accumulated at the upper end 43a1 of the ascending portion 43a. When the valve 71 is opened with oxygen accumulated at the upper end 43a1 of the ascending portion 43a, the gas phase in the first recovery path 43 and the liquid phase in the second recovery path 63 communicate with each other. As a result, oxygen is supplied to the cell 2 (the second chamber 25) by the same operation as in Embodiment 1, so that forced discharge occurs in the cell 2 (the second chamber 25), and the deviation of the potential balance between the first electrode 24 and the second electrode 26 is eliminated, and the decrease in charging efficiency and the decrease in capacity are eliminated.

[0036] [Embodiment 4] FIG. 5 is a schematic diagram showing the configuration of the redox flow battery 1D according to Embodiment 4. The same components as those of the redox flow battery 1C according to Embodiment 3 described above are denoted by the same reference numerals, and the description thereof is omitted.

[0037] As shown in FIG. 5, in the redox flow battery 1D according to Embodiment 4, the first recovery path 43 has an ascending portion 43a, a gas reservoir 46, and a descending portion 43b. The ascending portion 43a is a portion extending upward in the direction of gravity. As long as it extends upward in the direction of gravity, it is not limited to extending straight upward, and may be inclined obliquely or bent. The gas reservoir 46 is provided at the upper end 43a1 of the ascending portion 43a. The gas reservoir 46 is a portion for storing gas, and is composed of, for example, a spherical container. The descending portion 43b is a portion extending from the gas reservoir 46 toward the first tank 3, and the gas reservoir 46 is at the highest position in the direction of gravity. As long as the descending portion 43b has the gas reservoir 46 at the highest position in the direction of gravity, it may be inclined from the gas reservoir 46 toward the first tank 3, or may be bent along the path from the gas reservoir 46 toward the first tank 3. Thus, by having the first recovery path 43 include the ascending portion 43a, the gas reservoir 46, and the descending portion 43b, the gas containing oxygen generated at the first electrode 24 is stored in the gas reservoir 46.

[0038] Also, in the redox flow battery 1D according to Embodiment 4, one end of the adjustment path 7D is connected to the upper end of the gas reservoir 46, and the other end is connected to the upstream side of the second recovery path 63, preferably, the side close to the outlet of the cell 2.

[0039] In the redox flow battery 1D according to Embodiment 4, oxygen generated by the expansion of the charge storage rate range passes through the rising portion 43a and is stored in the gas reservoir 46. When the valve 71 is opened with gas accumulated in the gas reservoir 46, the gas phase in the gas reservoir 46 communicates with the liquid phase in the second recovery path 63. As a result, oxygen is supplied to the cell 2 (second chamber 25) by the same operation as in Embodiment 3, so that forced discharge occurs in the cell 2 (second chamber 25), and the deviation in the potential balance between the first electrode 24 and the second electrode 26 is eliminated, and the decrease in charging efficiency and the decrease in capacity are eliminated.

[0040] According to the redox flow battery 1D according to Embodiment 4, oxygen generated by the electrolysis of water accumulates in the gas reservoir 46 through the rising portion 43a, and is supplied to the second recovery path 63 through the adjustment path 7C by the opening of the valve 71. Therefore, oxygen generated by the electrolysis of water can be effectively collected and supplied to the second recovery path 63.

[0041] [Embodiment 5] FIG. 6 is a schematic diagram showing the configuration of a redox flow battery 1E according to Embodiment 5. The same components as those of the redox flow battery 1D according to Embodiment 4 described above are denoted by the same reference numerals and the description thereof is omitted.

[0042] As shown in FIG. 6, the redox flow battery 1E according to Embodiment 5 includes a level sensor 47 and a valve controller 48. The level sensor 47 detects the liquid level of the first electrolyte ES1 in the gas reservoir 46. When the oxygen accumulated in the gas reservoir 46 increases, the liquid level of the first electrolyte ES1 drops, and when the oxygen accumulated in the gas reservoir 46 decreases, the liquid level of the first electrolyte ES1 rises. The valve controller 48 is configured to open the valve 71 provided in the adjustment path 7E when the liquid level of the first electrolyte ES1 detected by the level sensor 47 is lower than a predetermined lower height, and to close the valve 71 when it is higher than a predetermined upper height.

[0043] The redox flow battery 1E according to Embodiment 5 allows the gas phase in the gas reservoir 46 to communicate with the liquid phase in the second recovery path 63 from when the liquid level of the first electrolyte ES1 detected by the level sensor 47 becomes lower than a predetermined lower height until it becomes higher than the predetermined upper height. As a result, oxygen is supplied to the cell 2 (second chamber 25) by the same operation as in Embodiment 3, causing forced discharge in the cell 2 (second chamber 25), eliminating the deviation in the potential balance between the first electrode 24 and the second electrode 26, and eliminating the decrease in charging efficiency and the decrease in capacity.

[0044] According to the redox flow battery 1E according to Embodiment 5, the valve 71 is opened when the liquid level of the first electrolyte ES1 detected by the level sensor 47 becomes lower than a predetermined lower height, and the valve 71 is closed when the liquid level of the first electrolyte ES1 becomes higher than a predetermined upper height. As a result, the oxygen accumulated in the gas reservoir 46 can be effectively supplied to the second recovery path 63. Thereby, the reaction in the cell 2 (second chamber 25) is effectively performed, and the discharge in the cell 2 (second chamber 25) is efficiently performed.

[0045] [Embodiment 6] FIG. 7 is a schematic diagram showing the configuration of the redox flow battery 1F according to Embodiment 6. The same components as those of the redox flow battery 1C according to Embodiment 3 described above are denoted by the same reference numerals and the description thereof is omitted.

[0046] As shown in FIG. 7, the redox flow battery 1F according to Embodiment 6 includes four cells 2. In the example shown in FIG. 4, the number of cells is not limited to this, and it may include any number of two or more cells 2. In the redox flow battery 1F according to Embodiment 6, the first supply path 41 branches so as to be connected to each of the four cells 2 (first chambers 23), and the first recovery path 43 is connected to each of the four cells (first chambers 23). The second supply path 61 branches so as to be connected to each of the four cells 2 (second chambers 25) in the same manner as the first supply path 41, and the second recovery path 63 is connected to each of the four cells 2 (second chambers 25) in the same manner as the first recovery path 43.

[0047] In the redox flow battery 1F according to Embodiment 6, for each cell 2, one potential difference detection device 8, adjustment path 7F, and valve 71 are provided. Therefore, in the example shown in FIG. 4, for the four cells 2, one potential difference detection device 8, adjustment path 7F, and valve 71 are provided respectively, for a total of four.

[0048] The potential difference detection device 8 is a device that detects the potential difference between the first electrode 24 and the second electrode 26 provided in the cell 2. The adjustment path 7F is provided between the first recovery path 43c and the second recovery path 63c extending from each of the cells 2 for each cell, and the gas phase of the first recovery path 43c and the liquid phase of the second recovery path 63c extending from each of the cells 2 communicate with each other. Therefore, it is provided so as to supply the gas contained inside the first recovery path 43c extending from each of the cells 2 to the second recovery path 63c.

[0049] In the redox flow battery 1F according to Embodiment 6, among the plurality of cells 2, the valve 71 for the cell 2 exceeding a predetermined potential difference is opened.

[0050] According to the redox flow battery according to Embodiment 6, among the plurality of cells 2, the valve 71 for the cell 2 exceeding a predetermined potential difference is opened. Therefore, oxygen generated from the first electrode 24 of the cell 2 exceeding the predetermined potential difference is supplied to the second recovery path 63 of the cell 2. As a result, oxygen generated in the cell 2 exceeding the predetermined potential difference is supplied to the second recovery path 63c connected to the cell 2 and mixed with the second electrolytic solution ES2. The second electrolytic solution ES2 mixed with oxygen passes through the second recovery path 63 and the second tank 5 and is distributed to each cell 2, and reacts with oxygen and the active material contained in the second electrolytic solution ES2 in the cell 2 having a large potential difference. As a result, discharging is performed, and the deviation in the potential balance between the first electrode 24 and the second electrode 26 in the cell 2 is eliminated.

[0051] The present invention is not limited to the above-described embodiments, and includes forms obtained by modifying the above-described embodiments and forms obtained by appropriately combining these forms. For example, as the aqueous solution containing the supporting electrolytes of the first electrolyte ES1 and the second electrolyte ES2, an acidic aqueous solution in which hydrogen chloride or the like is dissolved in addition to the sulfuric acid described above can be used. Further, as the aqueous solution containing the supporting electrolytes of the first electrolyte ES1 and the second electrolyte ES2, a neutral aqueous solution in which potassium chloride, sodium chloride or the like is dissolved, or an alkaline aqueous solution in which potassium hydroxide, sodium hydroxide or the like is dissolved can also be used. Further, for example, the active material dissolved in the first electrolyte ES1 or the second electrolyte ES2 may be a metal complex, air, halogen, organic molecule, etc. in addition to the metal ions such as vanadium described above, but the active material dissolved in at least one (or both) of the first electrolyte ES1 and the second electrolyte ES2 may be quinone or hydroquinone. As the metal ions, those that are deposited during reduction, such as zinc, may be used.

[0052] The content described in each of the above embodiments is understood as follows, for example.

[0053] The redox flow battery (1A to 1F) according to the aspect of [1] is at least one cell (2) in which a first chamber (23) where a first electrode (24) serving as an anode during charging is installed and a second chamber (25) where a second electrode (26) serving as a cathode during charging is installed are partitioned by a diaphragm (21), a first tank (3) for storing the first electrolyte (ES1), a first circulation device (4) including a first supply path (41) connecting the first tank (3) and the first chamber (23) and a first recovery path (43) connecting the first chamber (23) and the first tank (3), a second tank (5) for storing the second electrolyte (ES2), a second circulation device (6) including a second supply path (61) connecting the second tank (5) and the second chamber (25) and a second recovery path (63) connecting the second chamber (25) and the second tank (5), an adjustment path (7A to 7F) provided to supply the gas contained in the first tank (3) or the first recovery path (43) to the second recovery path (63), and includes.

[0054] According to such a configuration, since the gas contained in the first tank (3) or the first recovery path (43) is supplied to the second recovery path (63) by the adjustment paths (7A to 7F), the gas containing oxygen generated from the first electrode (24) is supplied to the second recovery path (63) by expanding the charge storage rate range of the redox flow batteries (1A to 1F). As a result, the oxygen contained in the gas is mixed with the second electrolytic solution (ES2) in the second recovery path (63) and supplied to the cell (2) (the second chamber (24)). Then, in the cell (2) (the second chamber (24)), the oxygen contained in the gas mixed with the second electrolytic solution (ES2) reacts with the active material contained in the second electrolytic solution (ES2), thereby performing forced discharge, eliminating the deviation in the potential balance between the first electrode (24) and the second electrode (26), and also eliminating the decrease in charge-discharge efficiency and the decrease in capacity. For example, when vanadium ions (V 2+ ) are used as the active material of the second electrolytic solution (ES2), the oxygen contained in the second electrolytic solution (ES2) reacts with vanadium ions (V 2+ ) (O2 + 4H + + 4V 2+ → 4V 3+ + 2H2O), and the V 2+ ions are discharged (forced discharge) to V 3+ . As a result, the deviation in the potential balance between the first electrode (24) and the second electrode (26) is eliminated, and the decrease in charge efficiency and the decrease in capacity are also eliminated.

[0055] [2] The redox flow batteries (1A, 1B) according to another aspect are the redox flow batteries (1A, 1B) described in [1], and the adjustment paths (7A, 7B) communicate with the gas phase in the first tank (3) and the liquid phase in the second recovery path (63).

[0056] According to such a configuration, the gas in the first tank (3) is supplied into the second recovery path (63) through the adjustment paths (7A, 7B), and in the second recovery path (63), the gas supplied from the adjustment paths (7A, 7B) is mixed with the second electrolytic solution (ES2).

[0057] [3]The redox flow battery (1B) according to another aspect is the redox flow battery (1B) described in [2], a gas sensor (31) for measuring the oxygen concentration in the gas phase in the first tank (3); a valve (71) provided in the adjustment path (7), the path being opened when the oxygen concentration measured by the gas sensor (31) exceeds a predetermined upper threshold value, and the path being closed when the oxygen concentration measured by the gas sensor (31) falls below a predetermined lower threshold value; and includes.

[0058] According to such a configuration, since the gas in the first tank (3) is supplied to the second recovery path (63) from when the oxygen concentration in the gas phase in the first tank (3) exceeds the upper threshold value until it falls below the lower threshold value, the gas (oxygen) in the first tank (3) can be effectively supplied to the second recovery path (63). Thereby, the gas in the first tank (3) is effectively mixed with the second electrolytic solution (ES2), the reaction in the cell (2) (second chamber (24)) is effectively performed, and the discharge in the cell (2) (second chamber (25)) is efficiently performed.

[0059] [4]The redox flow batteries (1C to 1F) according to another aspect are the redox flow batteries (1C to 1F) described in [1], the adjustment paths (7C to 7F) are in communication with the gas phase in the first recovery path (43) and the liquid phase in the second recovery path (63).

[0060] According to such a configuration, the gas in the first recovery path (43) is supplied into the second recovery path (63) through the adjustment paths (7C to 7F), and the gas supplied from the adjustment paths (7C to 7B) in the second recovery path (63) is mixed with the second electrolytic solution (ES2).

[0061] [5]The redox flow batteries (1C to 1F) according to another aspect are the redox flow batteries (1C to 1F) described in [4], The first recovery path (43) has an ascending portion (43a) extending upward in the direction of gravity and a descending portion (43b) extending from the upper end (43a1) of the ascending portion (43a) toward the first tank (3), with the upper end of the ascending portion being at the highest position in the direction of gravity. The adjustment path (7) is connected to the upper end (43a1) of the ascending portion (43a).

[0062] According to such a configuration, oxygen generated at the first electrode (24) passes through the ascending portion (43a) of the first recovery path (43) from the first chamber (23) and accumulates at the upper end (43a1) of the ascending portion (43a). Then, the oxygen accumulated at the upper end (43a1) of the ascending portion (43a) passes through the adjustment path (7) and is supplied to the second recovery path (63).

[0063] [6] A redox flow battery (1D, 1E) according to another aspect is the redox flow battery (1) described in [4], The first recovery path (43) has an ascending portion (43a) extending upward in the direction of gravity, a gas reservoir (46) provided at the upper end (43a1) of the ascending portion (43a), and a descending portion extending from the gas reservoir toward the first tank (3), with the gas reservoir being at the highest position in the direction of gravity. The adjustment path (7) is connected to the gas reservoir (46).

[0064] According to such a configuration, oxygen generated at the first electrode (24) accumulates in the gas reservoir (46) provided at the upper end (43a1) of the ascending portion (43a) of the first recovery path (43). Then, the oxygen accumulated in the gas reservoir (46) passes through the adjustment path (7) and is supplied to the second recovery path (63).

[0065] [7] A redox flow battery (1E) according to another aspect is the redox flow battery (1E) described in [6], a valve (71) provided in the adjustment path (7E) for opening or closing the adjustment path (7), a level sensor (47) for detecting the liquid level of the first electrolytic solution (ES1) in the gas reservoir (46). A valve controller (72) that opens the valve (71) when the liquid level of the first electrolyte (ES1) detected by the level sensor (48) is lower than a predetermined lower height, and closes the valve (71) when it is higher than a predetermined upper height, is provided.

[0066] According to such a configuration, the gas (oxygen) accumulated in the gas reservoir (46) is supplied to the second recovery path (63) from when the liquid level of the first electrolyte (ES1) in the gas reservoir (46) becomes lower than a predetermined lower height until it becomes higher than a predetermined upper height.

[0067] [8] A redox flow battery (1F) according to another aspect is the redox flow battery (1F) described in [1], wherein the at least one cell (2) includes at least two or more cells (2), for each of the at least two or more cells (2), a potential difference detection device (8) for detecting the potential difference of the cell, the adjustment path (7F), and a valve (71) for opening and closing the adjustment path (7F) are provided, among the at least two or more cells (2), the valve (71) for the cell (2) whose potential difference exceeds a predetermined potential difference is opened.

[0068] According to such a configuration, among at least two or more cells (2), the valve (71) for the cell (2) exceeding a predetermined potential difference is opened. Therefore, oxygen generated from the first electrode (24) of the cell (2) exceeding the predetermined potential is supplied to the second recovery path (63) of the cell (2). As a result, oxygen generated in the cell (2) exceeding the predetermined potential difference is supplied to the second recovery path (63a) connected to the cell (2) and mixed with the second electrolytic solution (ES2). The second electrolytic solution (ES2) mixed with oxygen passes through the second recovery path (63) and the second tank (5) and is distributed to each cell (2), and reacts with oxygen and the active material contained in the second electrolytic solution (ES2) in the cell (2) having a large potential difference. As a result, discharging is performed, and the deviation of the potential balance between the first electrode (24) and the second electrode (26) in the cell (2) is eliminated.

[0069] [9] The redox flow battery (1A to 1F) according to another aspect is the redox flow battery (1A to 1F) described in any one of [1] to [8], The inner wall (63a) of the second recovery path (63) has a spiral groove (63a1).

[0070] According to such a configuration, a swirling component is imparted to the second electrolytic solution (ES2) flowing through the second recovery path (63), and the second electrolytic solution (ES2) swirls in a spiral shape, so that the gas supplied from the adjustment path (7A to 7F) to the second recovery path (63) is effectively mixed with the second electrolytic solution (ES2). As a result, discharging in the cell (2) (the second chamber (24) is efficiently performed.

Explanation of symbols

[0071] 1A to 1F Redox flow battery 2 Cell 21 Diaphragm 23 First chamber 24 First electrode (positive electrode) 25 Second chamber 26 Second electrode (negative electrode) 3 First tank 31 Gas sensor 4 First circulation device 41 First supply path 42 First pump 43 First recovery path 43a Upright section 43a1 Upper end 43b Lowering section 43c First recovery path 44 First heat exchanger 46 Gas reservoir 47 Level sensor 48 Valve controller 5 Second tank 6 Second circulation device 61 Second supply path 62 Second pump 63 Second recovery path 63a Inner wall of the second recovery path 63a1 Spiral groove 63c Second recovery path 64 Second heat exchanger 7A - 7F Adjustment path 71 Valve 8 Potential difference detection device 100 AC - DC converter 200 AC power supply 300 Load ES1 First electrolyte (positive electrode electrolyte) ES2 Second electrolyte (negative electrode electrolyte)

Claims

1. At least one cell in which a first chamber where a first electrode serving as an anode during charging is installed and a second chamber where a second electrode serving as a cathode during charging is installed are partitioned by a diaphragm, a first tank for storing a first electrolyte, a first circulation device including a first supply path connecting the first tank and the first chamber and a first recovery path connecting the first chamber and the first tank, a second tank for storing a second electrolyte, a second circulation device including a second supply path connecting the second tank and the second chamber and a second recovery path connecting the second chamber and the second tank, an adjustment path provided to supply gas contained in the first tank or the first recovery path to the second recovery path, comprising the adjustment path is a redox flow battery that communicates with the gas phase in the first recovery path and the liquid phase in the second recovery path.

2. The first recovery path has an ascending portion extending upward in the direction of gravity and a descending portion extending from the upper end of the ascending portion toward the first tank, and the upper end of the ascending portion is at the highest position in the direction of gravity. The adjustment path is connected to the upper end of the ascending portion. The redox flow battery according to claim 1.

3. The first recovery path has an ascending portion extending upward in the direction of gravity, a gas reservoir provided at the upper end of the ascending portion, and a descending portion extending from the gas reservoir toward the first tank, and the gas reservoir is at the highest position in the direction of gravity. The adjustment path is connected to the gas reservoir. The redox flow battery according to claim 1.

4. A valve provided in the adjustment path for opening or closing the adjustment path, a level sensor for detecting the liquid level of the first electrolyte in the gas reservoir, a valve controller that opens the valve when the liquid level of the first electrolyte detected by the level sensor is lower than a predetermined lower height and closes the valve when it is higher than a predetermined upper height. The redox flow battery according to claim 3, comprising.

5. At least one cell in which a first chamber where a first electrode serving as an anode during charging is installed and a second chamber where a second electrode serving as a cathode during charging is installed are partitioned by a diaphragm, a first tank for storing a first electrolyte, a first circulation device including a first supply path connecting the first tank and the first chamber and a first recovery path connecting the first chamber and the first tank, a second tank for storing a second electrolyte, A second circulation device including a second supply path connecting the second tank and the second chamber, and a second recovery path connecting the second chamber and the second tank; An adjustment path provided to supply the gas contained in the first tank or the first recovery path to the second recovery path; Comprising; The at least one cell includes at least two or more cells; For each of the at least two or more cells, a potential difference detection device for detecting the potential difference of the cell, the adjustment path, and a valve for opening and closing the adjustment path are provided; A redox flow battery in which a valve for a cell exceeding a predetermined potential difference among the at least two or more cells is opened.

6. The redox flow battery according to any one of claims 1 to 5, wherein the inner wall of the second recovery path has a spiral groove.

7. At least one cell in which a first chamber where a first electrode serving as an anode during charging is installed and a second chamber where a second electrode serving as a cathode during charging is installed are partitioned by a diaphragm; A first tank for storing a first electrolyte; A first circulation device including a first supply path connecting the first tank and the first chamber, and a first recovery path connecting the first chamber and the first tank; A second tank for storing a second electrolyte; A second circulation device including a second supply path connecting the second tank and the second chamber, and a second recovery path connecting the second chamber and the second tank; An adjustment path provided to supply the gas contained in the first tank or the first recovery path to the second recovery path; Comprising; A redox flow battery in which the inner wall of the second recovery path has a spiral groove.

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