KR20110113513A - A redox flow secondary cell having metal foam electrodes - Google Patents

Abstract

The present invention relates to a redox flow secondary battery having a metal foam electrode, the present invention, a unit cell having a pair of electrodes formed of a metal foam that is a porous open structure; A pair of current collectors joined to both sides of the unit cell; It provides a redox flow secondary battery comprising a; and a pair of cell frames attached to each of the outer surface of the current collector.

Description

Redox flow secondary cell having a metal foam electrode

The present invention relates to a secondary battery, and more particularly, to a redox flow secondary battery using a metal foam (Metal Foam) having a porous open structure (electrode) as an electrode.

Electric power storage technology is an important technology for efficient use of the entire energy, such as efficient use of electric power, improvement of the power supply system's ability and reliability, the introduction of renewable energy that fluctuates over time, and the energy regeneration of the moving body. There is an increasing demand for possibilities and social contributions.

Adjusting the supply and demand balance of semi-autonomous regional power supply systems such as microgrids and properly distributing non-uniform outputs of renewable energy generation such as wind and solar power, and voltage and frequency fluctuations resulting from differences from existing power systems. In order to control the effect of the secondary battery is being actively researched and the expectation of the utilization of the secondary battery in these fields is increasing.

Looking at the characteristics required for the secondary battery to be used for high-capacity power storage, the energy storage density should be high, and the redox flow secondary battery is the most popular as a high capacity and high efficiency secondary battery that is most suitable for such characteristics.

In the redox flow secondary battery, the cell frame forms the outline of the entire cell, the center of the cell is separated by the ion exchange membrane, and the electrodes of the positive and negative electrodes are located around the ion exchange membrane, and the bipolar plate and the current collector are configured for electrical conduction. It consists of a positive and negative tank containing electrolyte, an inlet for the electrolyte and an outlet for the electrolyte to come back.

When the aqueous electrolyte is used in the redox flow secondary battery, the driving voltage is about 0.8 to 1.7 V, and the positive and negative electrolytes flowing from the positive and negative electrode tanks flow into the cell and are attached to the positive and negative electrodes, respectively. Charging and discharging proceed through an electrochemical reaction at.

In order to increase the output and energy efficiency of the redox flow battery as described above, the development of a redox flow secondary battery having a high driving voltage is in progress. For this purpose, a non-aqueous electrolyte should be used instead of an aqueous electrolyte. In order to develop a redox flow secondary battery to which such a non-aqueous electrolyte is applied, it is required to use an electrode having high affinity with a non-aqueous electrolyte and excellent electrical conductivity, and it is urgent to research and develop an electrode that satisfies these requirements.

In the case of electrode materials used in commercial water-based redox flow secondary batteries, carbon felt or carbon sheet is frequently used. However, in the case of the carbon-based electrode, since the affinity with the non-aqueous electrolyte solution is very low, it is very limited to apply to the non-aqueous redox flow secondary battery. For this reason, the method of using the electrode of the metal material which has high affinity with a non-aqueous electrolyte solution is proposed. However, the metal electrode has a high affinity with the non-aqueous electrolyte, but the energy efficiency is inevitably lowered because the activation area is much lower than that of the carbon electrode.

Therefore, an object of the present invention in view of the above-described conventional problem is a porous open structure form which can increase the activation area of a metal material electrode used to improve energy efficiency of a non-aqueous redox flow secondary battery. To provide a redox flow secondary battery having a metal foam (Metal Foam) of.

Another object of the present invention is to provide a redox flow secondary battery in which a plurality of unit cells having a porous open structure type metal foam electrode is formed.

Redox flow secondary battery according to a preferred embodiment of the present invention for achieving the above object, a unit cell including a pair of electrodes formed of a metal foam of a porous structure; A pair of current collectors joined to both sides of the unit cell; And a pair of cell frames attached to each of an outer surface of the current collector.

The electrode is formed through any one selected from aluminum (Al), copper (Cu), titanium (Ti), titanium alloy (Ti-Alloy), nickel (Ni), and nickel alloy (Ni-Alloy). do.

The hole size of the metal foam is characterized in that 0.45 mm to 5 mm.

The electrode has a thickness of 3 mm to 10 mm.

The unit cell includes an ion exchange membrane; The pair of electrodes bonded to both sides of the ion exchange membrane and including an anode and a cathode; And a pair of plates, one surface of which is bonded to an outer surface of each of the pair of electrodes and the other surface of which is bonded to the current collector.

The electrode may be attached to the plate by using silver paste or carbon paste on the inner surface of the metal foam.

The unit cell is characterized in that for generating electricity by the redox reaction through the ion exchange membrane between the electrodes.

The current collector draws out the generated electricity through the plate.

In addition, the secondary battery is a positive electrode and a negative electrode tank disposed on the left and right of each of the cell frame to store the electrolyte to withdraw; A pump connected to the anode and cathode tanks to supply the electrolyte; An inlet connecting the pump and the cell frame such that the electrolyte enters the unit cell through the cell frame; And an outlet for connecting the cell frame so that the electrolyte flowing out of the unit cell is introduced into the positive and negative electrode tanks.

Here, the electrolyte is characterized in that a non-aqueous electrolyte is used.

On the other hand, the secondary battery is characterized in that it is driven in the voltage range of 1.5V to 3.0V.

Redox flow secondary battery according to another embodiment of the present invention for achieving the above object, a pair of cell frames facing each other formed spaced apart; A pair of current collectors attached to each of inner surfaces of the pair of cell frames; And at least two unit cells formed between the pair of current collectors, wherein the unit cells include a pair of electrodes formed of a metal foam having a porous structure.

The at least two unit cells may be connected in series with each other.

The electrode is formed through any one selected from aluminum (Al), copper (Cu), titanium (Ti), titanium alloy (Ti-Alloy), nickel (Ni), and nickel alloy (Ni-Alloy). do.

The hole size of the metal foam is characterized in that 0.45 to 5 mm.

The electrode has a thickness of 3 mm to 10 mm or less.

The unit cell includes an ion exchange membrane; The pair of electrodes bonded to both sides of the ion exchange membrane and including an anode and a cathode; And a pair of plates, one surface of which is bonded to an outer surface of each of the pair of electrodes and the other surface of which is bonded to the current collector.

The electrode may be attached to the plate by using silver paste or carbon paste on the inner surface of the metal foam.

The unit cell is characterized in that for generating electricity by the redox reaction through the ion exchange membrane between the electrodes.

The current collector draws out the generated electricity through the plate.

In addition, the secondary battery is a positive electrode and a negative electrode tank disposed on the left and right of each of the cell frame to store the electrolyte to withdraw; A pump connected to the anode and cathode tanks to supply the electrolyte; An inlet connecting the pump and the cell frame such that the electrolyte enters the unit cell through the cell frame; And an outlet for connecting the cell frame so that the electrolyte flowing out of the unit cell is introduced into the positive and negative electrode tanks.

Here, the electrolyte is characterized in that a non-aqueous electrolyte is used.

On the other hand, the secondary battery is characterized in that it is driven in the voltage range of 1.5V to 3.0V.

According to the present invention as described above, the metal foam electrode structure for the non-aqueous redox flow secondary battery not only has a high electrolyte affinity and excellent electrical conductivity which is an advantage of the existing metal material electrode but also of the metal material electrode Structural improvement of the small activation area, which was a disadvantage, has the effect of improving the energy efficiency of the non-aqueous redox flow secondary battery.

1 and 2 are views for explaining a secondary battery according to an embodiment of the present invention.
3 is a photograph of a microstructure of an electrode including a cathode and an anode in the secondary battery of FIGS. 1 and 2.
4 and 5 are views for explaining a secondary battery according to another embodiment of the present invention.
6 and 7 are graphs for explaining the effect of the secondary battery according to an embodiment of the present invention.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following description, only parts necessary for understanding the operation according to the embodiment of the present invention will be described, and the description of other parts will be omitted so as not to disturb the gist of the present invention.

First, a secondary battery according to an embodiment of the present invention will be described. 1 and 2 are views for explaining a secondary battery according to an embodiment of the present invention. 1 is an exploded view illustrating the disassembled components of a rechargeable battery according to an exemplary embodiment of the present invention. 2 is a cross-sectional view illustrating a cross section of a rechargeable battery according to an exemplary embodiment of the present invention.

1 and 2, a secondary battery according to an embodiment of the present invention is a redox flow secondary battery that is charged or discharged by using a redox reaction of a metal ion whose valence is changed. In addition, the redox flow secondary battery according to the embodiment of the present invention is driven in the voltage range of 1.5V to 3.0V.

Secondary battery according to an embodiment of the present invention is bonded to the outer surface of the unit cell 100 and the unit cell 100 having a plate-shaped multilayer structure, a pair of current collector 40 and each current collector 40 made of a plate shape It is bonded to the outer surface of the) includes a cell frame 50 formed in a plate shape.

Herein, the unit cell 100 includes a plate-shaped ion exchange membrane 10, an electrode 20, and a bipolar plate (hereinafter abbreviated as “plate”) 30, mainly around the ion exchange membrane 10. On both sides of the ion exchange membrane 10, a pair of electrodes 20 having a pair of anodes and a cathode are joined to face each other, and the plate 30 is bonded to the outer surface of the electrodes 20 of each of the anodes and cathodes. Have As described above, each of the plate-shaped ion exchange membrane 10, the electrode 20, and the plate 30 forms a single unit cell 100 in a multilayer structure. In the unit cell 100, a redox reaction of a metal ion having a valence is performed, and the redox reaction is performed between the electrodes 20 of the anode and the cathode through the ion exchange membrane 10. Electricity is generated by this redox reaction. As such, when electricity is generated at the positive electrode and the negative electrode 20 of the unit cell 100, the plate 30 and the current collector 40 draw out the generated electricity. The cell frame 50 maintains and supports the shapes of the ion exchange membrane 10, the pair of electrodes 20, the pair of plates 30, and the pair of current collectors 40 described above.

In addition, the secondary battery according to the embodiment of the present invention further includes a positive electrode tank 60 and a negative electrode tank 70, pumps 61 and 71, inlets 63 and 73, and outlets 65 and 75. It is configured by. The positive electrode tank 60 and the negative electrode tank 70 respectively store the positive electrode and the negative electrode electrolyte so that they can be withdrawn if necessary. Each of the positive electrode tank 60 and the negative electrode tank 70 uses a non-aqueous electrolyte as the positive electrode and the negative electrode electrolyte. The anode tank 60 and the cathode tank 70 are disposed on the left and right sides of the unit cell 100 corresponding to the anode and the cathode of the electrode 20 of the unit cell 100 described above, respectively. In addition, the anode tank 60 and the cathode tank 70 are connected to the cell frame 60 through the inlets 63 and 73 and the outlets 65 and 75. The inlets 63 and 73 are passages through which the electrolytes of the positive and negative electrode tanks 60 and 70 enter the unit cell 100, and the outlets 65 and 75 are passages through which the electrolytes reappear. In addition, the pumps 61 and 71 are for supplying the electrolyte from the positive electrode tank 60 and the negative electrode tank 70 and supplying the electrolyte to the unit cell 100. Each of the positive electrode tank 60 and the negative electrode tank ( Interposed between 70) and inlets (63, 73). That is, the electrolyte drawn out from the positive electrode tank 60 and the negative electrode tank 70 is connected to the pumps 61 and 71, the inlets 63 and 73, each cell frame 50, and each current collector 40. It is supplied to the unit cell 100, and is stored in the positive electrode tank 60 and the negative electrode tank 70 in the reverse order.

3 is a photograph of a microstructure of an electrode including a cathode and an anode in the secondary battery of FIGS. 1 and 2.

As shown in FIG. 3, the metal used as the electrode 20 in the embodiment of the present invention is a metal foam, and may be referred to as a "metal sponge". The metal foam is made of a porous open structure having a plurality of pores, like a sponge. Therefore, the metal foam has a wide cross section. For this reason, the disadvantage of the metal electrode having a small reaction area can be compensated. In addition, the metal foam can improve the energy efficiency because the flow of the electrolyte is very good due to the porous structure. In addition, since the metal foam has the high conductivity of the metal material at the same time, the voltage efficiency can be improved. Herein, the smaller the size of the pores in the metal foam of the porous structure, the more preferable, and may be formed in a size of 0.45 mm to 5 mm. In particular, the size of the holes preferably has a size of 0.5 mm or less.

As described above, the electrode 20 using the metal foam is attached to the inner surface of the plate 30. The metal foam electrode 20 is attached to the plate 30 using silver paste or carbon paste on the inner surface of the metal foam.

Since the thickness and size of the metal foam electrode 20 depend on the capacity and output of the battery, it is not necessary to define the range, but the thickness of the electrode 20 is preferably 3 mm to 10 mm because it is related to electrolyte leakage. Do.

Metal materials that can be used as metal foams include aluminum (Al), copper (Cu), titanium (Ti), titanium alloys (Ti-Alloy), nickel (Ni), nickel alloys (Ni-Alloy), and the like. In the metal material, one having a porous open structure type structure is used.

In addition, the secondary battery according to the embodiment of the present invention may be applied to a secondary battery in which a plurality of unit cells 100 are connected in series by a plate 30. A secondary battery using the plurality of unit cells 100 will be described.

4 and 5 are views for explaining a secondary battery according to another embodiment of the present invention. 4 is an exploded view illustrating the components of the secondary battery according to another embodiment of the present invention. 5 is a cross-sectional view illustrating a cross section of a rechargeable battery according to another exemplary embodiment of the present invention.

4 and 5, a secondary battery according to an embodiment of the present invention is a redox flow secondary battery that is charged or discharged by using a redox reaction of a metal ion having a valence. In addition, the redox flow secondary battery according to the embodiment of the present invention is driven in the voltage range of 1.5V to 3.0V.

A secondary battery according to another embodiment of the present invention includes a pair of cell frames 50, a pair of current collectors 40, and a plurality of unit cells 100.

The pair of cell frames 50 face each other at a predetermined interval. As such, each of the pair of current collectors 40 is bonded to the inner surface of each of the pair of cell frames 50 facing each other. A plurality of unit cells 100 are interposed between the current collector 50. As described above, the plurality of unit cells 100 includes an ion exchange membrane 10, an electrode 20 including an anode and a cathode, and a plate 30. As shown, the plurality of unit cells 100 are connected in series with each other, and share the plate 30 of the portion to be connected to each other. For example, FIGS. 4 and 5 illustrate secondary batteries in which three unit cells 100 are formed. As shown, since three unit cells share two plates 30 to be connected, there are four plates 30.

As described above, in the structure in which the plurality of unit cells 100 are connected in series, each electrode 20 is made of a metal foam, as shown in FIG. 3, and the metal foam is formed of a plurality of holes such as a sponge. porous structure having a pore). The smaller the size of the pores in the metal foam of the porous structure, the more preferable, and may be formed in the size of 0.45 mm to 5 mm. In particular, the size of the holes preferably has a size of 0.5 mm or less. As described above, the electrode 20 using the metal foam is attached to the inner surface of the plate 30. The metal foam electrode 20 is attached to the plate 30 using silver paste or carbon paste on the inner surface of the metal foam. Since the thickness of the electrode 20 is related to electrolyte leakage, the thickness of the electrode 20 is preferably 3 mm to 10 mm. Metal materials that can be used as the metal foam include aluminum (Al), copper (Cu), titanium (Ti), titanium alloys (Ti-Alloy), nickel (Ni), nickel alloys (Ni-Alloy).

In addition, although not shown in Figures 4 and 5, the secondary battery according to another embodiment of the present invention is a positive electrode tank 60, a negative electrode tank 70, pumps (61, 71), inlet (63, 73 and outlets 65 and 75 further.

The positive electrode tank 60 and the negative electrode tank 70 store a positive electrode and a negative electrode electrolyte so that they can be withdrawn if necessary, and use a non-aqueous electrolyte as the positive electrode and the negative electrode, respectively. The anode tank 60 and the cathode tank 70 are disposed on the left and right sides of the unit cell 100 corresponding to the anode and the cathode of the electrode 20 of the unit cell 100 described above, respectively. In addition, the anode tank 60 and the cathode tank 70 are connected to the cell frame 60 through the inlets 63 and 73 and the outlets 65 and 75. In addition, the pumps 61 and 71 extract the electrolyte from the anode tank 60 and the cathode tank 70 and supply the electrolyte to the unit cell 100, and each of the anode tank 60 and the cathode tank 70 is provided. And an inlet (63, 73). That is, the electrolyte drawn out from the positive electrode tank 60 and the negative electrode tank 70 is connected to the pumps 61 and 71, the inlets 63 and 73, each cell frame 50, and each current collector 40. It is supplied to the unit cell 100, and is stored in the positive electrode tank 60 and the negative electrode tank 70 in the reverse order.

Next, the effect of the secondary battery according to the embodiment of the present invention will be described by comparing the general secondary battery. 6 and 7 are graphs for explaining the effect of the secondary battery according to an embodiment of the present invention.

First, according to an embodiment of the present invention, a metal foam having a thickness of 2 mm made of nickel was cut into a size of 50 mm × 60 mm to prepare an electrode 20 of a positive electrode and a negative electrode. The unit cell 100 is formed using the metal foam electrode 20. In this case, in the unit cell 100, the plate 30 used graphite, and the ion exchange membrane 10 used Nafion. On the other hand, as a comparative example, a general secondary battery uses a nickel-mesh metal material having a small reaction area as a positive electrode and a negative electrode.

Subsequently, the internal ohmic resistance (IOR) and charge transfer (Charge Transfer) resistance of each of the secondary batteries using the metal foam electrode and the mesh structure electrode were measured, charged and discharged, and the results are shown in FIGS. 6 and 7. .

FIG. 6 is a graph illustrating a comparison of internal ohmic resistance (IOR) and charge transfer resistance measurement results of a secondary battery using a metal foam electrode and a secondary battery using a mesh electrode.

Here, reference numeral (a) is a measurement result of a unit cell to which a mesh electrode is applied as a comparative example, and reference numeral (b) shows a measurement result of a unit cell to which a metal foam electrode is applied.

As shown in FIG. 4, in the case of (a) using the mesh electrode, the IOR is 0.033 and the charge transfer resistance is 0.066. On the other hand, in the case of (b) using the metal foam electrode, the IOR is 0.032 and the charge transfer resistance is 0.036.

As can be seen from the disclosed results, since the electrodes of (a) and (b) are the same metal material, it can be confirmed that the IOR, which is a value related to electrical conductivity, has almost the same value. On the other hand, when the mesh electrode is used, the charge transfer resistance is greater than when the metal foam is used. This is because the reaction area in the case of using the mesh electrode is smaller than in the case of using the metal foam. This result indicates that when the metal foam electrode is used, the resistance is reduced, which is effective in increasing the output characteristics.

FIG. 7 is a graph illustrating unit cell charging and discharging results of a secondary battery using a metal foam electrode and a secondary battery using a mesh electrode. Here, reference numeral (a) is a measurement result of a unit cell to which a nickel mesh electrode is applied as a comparative example, and reference numeral (b) shows a measurement result of a unit cell to which a metal foam electrode is applied.

As shown in FIG. 5, in the case of (a) using the mesh electrode, the energy efficiency is 61%. On the other hand, in the case of using the metal foam electrode (b) shows an energy efficiency of 85%. These results indicate that the metal foam electrode structure has a higher energy efficiency.

As described above, according to the embodiment of the present invention, the metal foam is used as the electrode 20, and the metal foam is made of a porous open structure having a plurality of pores, such as a sponge, so that the cross-sectional area is wide. For this reason, the disadvantage of the metal electrode having a small reaction area can be compensated. In addition, the metal foam can improve the energy efficiency because the flow of the electrolyte is very good due to the porous structure. In addition, since the metal foam has the high conductivity of the metal material at the same time, the voltage efficiency can be improved. That is, according to the embodiment of the present invention, not only has a high electrolyte affinity and excellent electrical conductivity, which are advantages of the existing metal electrode, but also structurally improves a small activation area, which is a disadvantage of the metal electrode, by non-aqueous redox flow secondary. There is an effect of improving the energy efficiency of the battery.

While the present invention has been described with reference to several preferred embodiments, these embodiments are illustrative and not restrictive. As such, those of ordinary skill in the art will appreciate that various changes and modifications can be made according to equivalents without departing from the spirit of the present invention and the scope of rights set forth in the appended claims.

100: unit cell
10: ion exchange membrane
20 electrode
30: plate
40: current collector
50: cell frame
60: anode tank
70: cathode tank
61, 71: Pump
63, 73: inlet
65, 75: outlet

Claims (23)

In a redox flow secondary battery,
A unit cell including a pair of electrodes formed of a metal foam having a porous structure;
A pair of current collectors joined to both sides of the unit cell; And
Redox flow secondary battery comprising a; a pair of cell frames attached to each of the outer surface of the current collector. The method of claim 1, wherein the electrode
Redox formed through any one selected from aluminum (Al), copper (Cu), titanium (Ti), titanium alloys (Ti-Alloy), nickel (Ni), and nickel alloys (Ni-Alloy). Flow secondary battery. The method of claim 1,
Redox flow secondary battery, characterized in that the pore size of the metal foam is 0.45 mm to 5 mm. The method of claim 1, wherein the electrode
Redox flow secondary battery having a thickness of 3 mm to 10 mm. The method of claim 1, wherein the unit cell
Ion exchange membrane;
The pair of electrodes bonded to both sides of the ion exchange membrane and including an anode and a cathode; And
Redox flow secondary battery, characterized in that it comprises a pair of plates one side is bonded to the outer surface of each of the pair of electrodes and the other side is bonded to the current collector. The method of claim 5, wherein the electrode
A redox flow secondary battery, wherein a silver paste or carbon paste is attached to the plate using an inner surface of the metal foam. The method of claim 5, wherein the unit cell
A redox flow secondary battery, characterized in that to generate electricity through the ion exchange membrane between the electrodes in accordance with a redox reaction. The method of claim 7, wherein the current collector
Redox flow secondary battery, characterized in that for extracting the generated electricity through the plate. The method of claim 1,
An anode and a cathode tank disposed on left and right sides of each of the cell frames to store the electrolyte so as to extract the electrolyte;
A pump connected to the anode and cathode tanks to supply the electrolyte;
An inlet connecting the pump and the cell frame such that the electrolyte enters the unit cell through the cell frame; And
A redox flow secondary battery further comprising: an outlet for connecting the cell frame so that the electrolyte flowing out of the unit cell is introduced into the positive and negative electrode tanks. The method of claim 9, wherein the electrolyte
Redox flow secondary battery, characterized in that a non-aqueous electrolyte is used. The method of claim 1, wherein the secondary battery
Redox flow secondary battery, characterized in that driven in the voltage range of 1.5V to 3.0V. In a redox flow secondary battery,
A pair of cell frames facing each other and spaced apart;
A pair of current collectors attached to each of inner surfaces of the pair of cell frames; And
And at least two unit cells formed between the pair of current collectors,
The unit cell comprises a pair of electrodes formed of a metal foam of a porous structure redox flow secondary battery. The method of claim 12,
The at least two unit cells are connected to each other in series redox flow secondary battery. The method of claim 12, wherein the electrode
Redox formed through any one selected from aluminum (Al), copper (Cu), titanium (Ti), titanium alloys (Ti-Alloy), nickel (Ni), and nickel alloys (Ni-Alloy). Flow secondary battery. The method of claim 12,
Redox flow secondary battery, characterized in that the pore size of the metal foam is 0.45 mm to 5 mm. The method of claim 12, wherein the electrode
Redox flow secondary battery having a thickness of 3 mm to 10 mm or less. The method of claim 12, wherein the unit cell
Ion exchange membrane;
The pair of electrodes bonded to both sides of the ion exchange membrane and including an anode and a cathode; And
Redox flow secondary battery, characterized in that it comprises a pair of plates one side is bonded to the outer surface of each of the pair of electrodes and the other side is bonded to the current collector. The method of claim 17, wherein the electrode
A redox flow secondary battery, wherein a silver paste or carbon paste is attached to the plate using an inner surface of the metal foam. The method of claim 17, wherein the unit cell
A redox flow secondary battery, characterized in that to generate electricity through the ion exchange membrane between the electrodes in accordance with a redox reaction. The method of claim 19, wherein the current collector
Redox flow secondary battery, characterized in that for extracting the generated electricity through the plate. The method of claim 12,
An anode and a cathode tank disposed on left and right sides of each of the cell frames to store the electrolyte so as to extract the electrolyte;
A pump connected to the anode and cathode tanks to supply the electrolyte;
An inlet connecting the pump and the cell frame such that the electrolyte enters the unit cell through the cell frame; And
A redox flow secondary battery further comprising: an outlet for connecting the cell frame so that the electrolyte flowing out of the unit cell is introduced into the positive and negative electrode tanks. 22. The redox flow secondary battery of claim 21, wherein the electrolyte is a non-aqueous electrolyte. The redox flow secondary battery of claim 12, wherein the secondary battery is driven in a voltage range of 1.5 V to 3.0 V.

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