JP2021026824A - Redox flow type secondary cell - Google Patents

Abstract

To provide a redox flow type secondary cell that greatly reduces the flow resistance of an active material liquid flowing through an electrode chamber and improved in flowability regarding the physical properties of the active material liquid.SOLUTION: In a redox flow type secondary cell configured such that a plurality of electric cells each having an electrode chamber for performing battery reaction are electrically stacked in series, and an active material liquid which is a battery active material can be shared among the plurality of electric cells, the width of the electrode chamber between a multi-pole partition plate and a diaphragm is 0.5 to 2 mm, and the apparent linear velocity when the active material liquid flows through the electrode chamber is in a range of 3 to 7 cm/sec.SELECTED DRAWING: None

Description

The present invention relates to a redox flow type secondary battery in which the flow resistance of the active material liquid flowing in the electrode chamber is greatly reduced and the flowability is improved.

In recent years, as a measure against global warming, the movement toward a low-carbon society has become active, and renewable energy is in the limelight. Renewable energy is mainly supplied to homes and factories in the form of electricity by solar power generation and wind power generation, but has the disadvantage of large fluctuations due to the weather.

As a result, these power generations cause problems such as voltage rise, frequency fluctuation, and generation of surplus power. As one of the methods to solve this problem, the electric energy storage system is attracting attention, and the system using the storage battery is regarded as the most promising.

There are several types of storage batteries (also called secondary batteries) that enable charging and discharging, and among them, lithium-ion batteries, sodium-sulfur batteries (NAS batteries), lead-acid batteries, and redox flow batteries are famous. is there. Lead-acid batteries have long been used as batteries for automobiles and motorcycles, and have a wealth of experience as small storage batteries. Lithium-ion batteries also have many achievements as small batteries. NAS batteries have an extremely high energy density, and because of their high charge / discharge efficiency, they are widely used in power leveling applications in substations.

The redox flow battery has the advantages of "high degree of freedom in design", "high safety" and "normal temperature operation" as compared with the above storage battery. Redox flow batteries with such advantages are currently regarded as one of the promising means for leveling renewable energy all over the world.
Since the development of redox flow batteries that use vanadium ions as the active material of positive and negative electrolytes, their practical application has progressed all at once, and it continues to this day.

The V / V-based redox flow battery is a battery in which an electrode made of carbon fiber or the like is placed in a positive electrode solution and a negative electrode solution, and both the positive electrode solution and the negative electrode solution are vanadium-based electrolytic solutions. The positive electrode side and the negative electrode side are separated by a diaphragm that allows only hydrogen ions to pass through without passing the electrolytic solution on both electrode sides. During charging and discharging, the positive electrode liquid is connected to a tank outside the battery and circulates in a path connecting the positive electrode chamber and the tank by a pump outside the battery. The negative electrode liquid also circulates in the same system as the positive electrode liquid.

Conventionally, in a redox flow battery, in order to improve the overall energy efficiency, it is required to reduce the internal resistance (cell resistance) and the pressure loss when the electrolytic solution is permeated through the electrode.

Patent Document 1 discloses a technique for reducing the pressure loss of the liquid supply by devising the shape of the flow path of the active material liquid.

Patent Document 2 discloses a redox flow battery having a low cell resistance by eliminating a portion where the flow of the electrolytic solution is non-uniform.

Patent Document 3 proposes a redox battery capable of reducing the internal resistance of the battery cell without reducing the thickness of the battery cell and reducing the pump power loss due to the circulation of the electrolytic solution, which is special. A liquid permeable porous electrode is disclosed.

Japanese Unexamined Patent Publication No. 2016-207669 Japanese Unexamined Patent Publication No. 2019-024008 Patent No. 3496385

All of Patent Documents 1 to 3 exert the effect of reducing the flow pressure loss of the electrolytic solution (active material solution) by devising the flow path of the electrolytic solution and the electrode itself, but the composition and concentration of the electrolytic solution have changed. In some cases, the pressure loss could not be reduced.

Therefore, an object of the present invention is to provide a redox flow type secondary battery in which the flow resistance of the active material liquid flowing in the electrode chamber is greatly reduced and the flowability is improved, focusing on the physical properties of the active material liquid. is there.

Other problems of the present invention will be clarified by the following description.

The above problems are solved by the following inventions.

(Claim 1)
A redox flow type in which a plurality of cell cells having an electrode chamber for performing a battery reaction are electrically stacked in series, and an active material liquid which is a battery active material can be shared among the plurality of cell cells. In the secondary battery
The width of the electrode chamber between the multi-pole partition plate and the diaphragm is 0.5 to 2 mm.
Further, a redox flow type secondary battery characterized in that the apparent linear velocity when the active material liquid flows through the electrode chamber is in the range of 3 to 7 cm / sec.
(Claim 2)
The redox flow type secondary battery according to claim 1, wherein the height of the electrode chamber is in the range of 100 to 500 mm.
(Claim 3)
The active material solution is contained so that the vanadium concentration is 1.2 M or more and 1.8 M or less, and the total sulfate root concentration including hydrogen sulfate root is 4 M or more and 8 M or less, and in the Raman spectrum on the high frequency side, 3200 cm ^{−. The redox flow according to claim 1 or 2, wherein the shoulder peak showing a hydrogen bond in 1} is not observed, and even if the shoulder peak is observed, it is 1% or less of the peak for OH of ^{3400 to 3500 cm -1.} Type secondary battery.
(Claim 4)
The active material solution is contained so that the vanadium concentration is 1.2 M or more and 1.8 M or less, and the total sulfate root concentration including hydrogen sulfate root is 4 M or more and 8 M or less, and the chemical shift in the proton nuclear magnetic resonance absorption spectrum. The redox flow type secondary battery according to claim 1 or 2, wherein the value is 30 ppm or less (however, 0 ppm is not included).
(Claim 5)
The active material solution is contained so that the vanadium concentration is 1.2 M or more and 1.8 M or less, and the total sulfate root concentration including hydrogen sulfate root is 4 M or more and 8 M or less, and the volume resistivity at 25 ° C. is 7.0 Ωcm. The redox flow type secondary battery according to claim 1 or 2 below.
(Claim 6)
The active material solution is contained so that the vanadium concentration is 1.2 M or more and 1.8 M or less, and the total sulfate root concentration including hydrogen sulfate root is 4 M or more and 8 M or less, and the viscosity at 25 ° C. is 10 mPa · sec or less. The redox flow type secondary battery according to claim 1 or 2.

According to the present invention, paying attention to the physical characteristics of the active material liquid, a redox flow type secondary battery in which the flow resistance when the electrolytic liquid which is the active material liquid is circulated in the electrode chamber is greatly reduced and the flowability is improved. Can be provided.

The figure which conceptually explains an example of the redox flow type secondary battery of this invention. Schematic cross-sectional view showing an embodiment of a cell stack used in the redox flow type secondary battery according to the present invention. Diagram of Raman spectrum on the high frequency side of the electrolyte used in this example The figure which shows the chemical shift of the electrolytic solution used in this Example

Hereinafter, embodiments for carrying out the present invention will be described in detail.

FIG. 1 is a diagram conceptually explaining an example of the redox flow type secondary battery of the present invention.

In FIG. 1, 1 is a positive electrode chamber, 2 is a negative electrode chamber, and 3 is a diaphragm that separates the positive electrode chamber 1 and the negative electrode chamber 2.
Reference numeral 4 denotes a spacer, which forms a gap corresponding to each of the positive electrode chamber 1 and the negative electrode chamber 2.
A positive electrode 11 is provided in the positive electrode chamber 1, and a negative electrode 21 is provided in the negative electrode chamber 2. A carbon electrode can be used as the positive electrode 11 and the negative electrode 21.

The positive electrode chamber 1 is provided with an inflow port 12 for flowing in the positive electrode active material liquid and an outflow port 13 for flowing out the positive electrode active material liquid.

The positive electrode active material liquid stored in the positive electrode active material liquid tank 14 is configured to flow into the positive electrode chamber 1 via the inflow pipe 16 connected to the inflow port 12 by driving the pump 15. .. As a result, the battery reaction takes place in the positive electrode chamber 1.

Further, the positive electrode active material liquid flowing out from the outflow port 13 is configured to be returned to the positive electrode active material liquid tank 14 via the outflow pipe 17 connected to the outflow port 13.

In this way, a circulation system for circulating and supplying the positive electrode active material liquid from the positive electrode active material liquid tank 14 to the positive electrode chamber 1 is configured.

The negative electrode chamber 2 is provided with an inflow port 22 for flowing in the negative electrode active material liquid and an outflow port 23 for flowing out the negative electrode active material liquid.

The negative electrode active material liquid stored in the negative electrode active material liquid tank 24 is configured to flow into the negative electrode chamber 2 via the inflow pipe 26 connected to the inflow port 22 by driving the pump 25. .. As a result, the battery reaction takes place in the negative electrode chamber 2.

Further, the negative electrode active material liquid flowing out from the outlet 23 is configured to be returned to the negative electrode active material liquid tank 24 via the outflow pipe 27 connected to the outflow port 23.

In this way, a circulation system for circulating and supplying the negative electrode active material liquid from the negative electrode active material liquid tank 24 to the negative electrode chamber 2 is configured.

Hereinafter, in the present specification, the positive electrode chamber 1 and the negative electrode chamber 2 may be referred to simply as electrode chambers, if necessary.

The diaphragm 3 plays a role of allowing the permeation of protons, which are charge carriers inside the battery, during charging and discharging, and preventing the permeation of vanadium in order to prevent self-discharge. As the diaphragm 3, for example, an ion exchange membrane or the like can be preferably used.

In the illustrated example, the conductive sheets 5 and 5 are provided so as to come into contact with the carbon electrode 11 in the positive electrode chamber 1 and the carbon electrode 21 in the negative electrode chamber 2, respectively.

A battery structure is formed between one conductive sheet 5 and the opposite conductive sheet 5 by components such as a positive electrode chamber, a negative electrode chamber, a carbon electrode, and a battery active material liquid, and this one battery. The cell having a structure is the cell cell according to the present invention.

In the case of one cell cell, the entire cell cell is sandwiched by the pressing plates 6 and 6 from the outside of the conductive sheets 5 and 5.

In the present invention, a stack structure in which a plurality of these cells are stacked is preferable, and as shown in FIG. 1, a cell unit is used by using a partition plate such as a bipolar plate (bipolar plate) as the conductive sheets 5 and 5. It is possible to construct a laminated structure (stack structure) in which a plurality of the above are laminated.
In that case, holding plates 6 and 6 are provided at both ends of the plurality of cells.

The positive electrode 11 and the negative electrode 21 are electrically connected to an external circuit (including input / output terminals and the like) via conductive sheets 5 and 5, respectively.

In the redox flow type secondary battery, the positive electrode active material liquid and the negative electrode active material liquid are circulated and supplied to the positive electrode chamber 1 and the negative electrode chamber 2, respectively, and the electrode reaction (oxidation-reduction reaction) of the active material in the active material liquid at both electrodes. Charging and discharging is performed accordingly. For the electrode reaction during charging and discharging of the reddock flow type secondary battery, known reactions can be referred to.

The description of FIG. 1 is based on an example of a “flow by” method. The "flow by" method is an example of how to flow the battery active material, and in the electrode chamber (electrolytic cell), the battery active material liquid or the electrolyzed material liquid is poured in parallel with the electrode surface direction of the electrode formed in a sheet shape. It is a method of distribution.

On the other hand, there is also a "flow through" method in which the liquid is permeated so as to cross the electrode.

Regarding the "flow by" method and the "flow through" method, J. Trainham, J. Newman, “A comparison between flow-through and flow-by porous electrodes for redox energy storage”, Electrochimica Acta, 26 (4), 455 (1981) can be referred to.

Next, an example of the cell stack structure that can be adopted in the present invention will be described with reference to FIG.

FIG. 2 is a schematic cross-sectional view showing an embodiment of a cell stack used in the redox flow type secondary battery according to the present invention. In the present embodiment, in FIG. 1, the battery active material liquid flows in from the lower side to the upper side of the electrode chamber, and in FIG. 2, it is described in the opposite direction, but both are based on the same “flow by” method. is there. Therefore, in the redox flow type secondary battery shown in FIG. 2, as shown in FIG. 1, the battery active material liquid may flow in from below and flow out from above.

The cell stack 100 includes a plurality of cells 100A, 100B, 100C, .... In the illustrated example, three cells 100A, 100B, 100C are shown.
Each cell 100A, 100B, 100C is composed of a pair of cells of cell 101 and 102, a pair of cells of cell 103 and 104, and a pair of cells of cell 105 and 106.

In cells 101 to 106, cell internal spaces 113 to 118, which are defined by cell frame members 107 to 112, are formed.

The active material liquid stored in the storage tank (not shown) can be passed through the internal spaces 113 to 118 of each cell by a circulation pump (not shown).

Septums 119, 120, and 121 are provided between the cells 101 and 102, the cells 103 and 104, and the cells 105 and 106, respectively.

The means for fixing the cell frame members 107 to 112 and the diaphragms 119, 120, 121 are not particularly limited.

The other end side of the cell frame members 107 to 112 is closed by 122, 123, 124, 125 which are partition plates such as a conductive sheet.

Terminals (not shown) are connected to the partition plates 122, 123, 124, and 125, respectively. In this embodiment, the partition plates 122 and 124 are positive electrodes (+ poles), and the partition plates 123 and 125 are negative electrodes (-poles). Positive direct current electricity is connected to the positive electrode partition plates 122 and 124, and negative direct current electricity is connected to the negative electrode partition plates 123 and 125.

Reference numeral 128 is an inflow pipe for the active material liquid to flow in, and 129 is an outflow pipe for the active material liquid to flow out. Further, 130 is an inflow port where the active material liquid from the inflow pipe 128 flows into the cells 101 to 106, and 131 is an outflow outlet where the active material liquid flows out from the cells 101 to 106 to the outflow pipe 129.

The inflow method from the inflow pipe 128 to the cells 101 to 106 via the inflow port 130 is not particularly limited. Further, the outflow method from the cells 101 to 106 to the outflow pipe 129 via the outflow port 131 is not particularly limited.

The inside of the cell (inside the electrode chamber) is filled with a carbon fiber non-woven fabric (carbon felt) or the like that undergoes a charge transfer reaction with an active material (vanadium ion).

It is preferable to use carbon felt having a small fiber diameter for the carbon electrode because the mass transfer is improved and the diffusion of the electrolyzed substance becomes more multidimensional (for example, 2D to 2.5D diffusion). Further, when the fiber surface is graphitic carbon, the electrode reactivity (charge transfer reactivity) is also improved. Due to these synergistic actions, the carbon electrode can electrolyze the substance to be electrolyzed with a high current density. Therefore, since the above-mentioned effects can be obtained, it is particularly preferable to use the carbon electrode as the electrode of the redox flow type secondary battery.

In the present embodiment, as the carbon electrode, one in which a small-diameter carbon fiber and / or a carbon fiber fragment is supported on a carbon fiber felt, or one obtained by an oxidizing treatment can also be used. The carbon electrodes obtained by these methods do not require large-scale equipment as in the case of the vapor phase growth method, are low in cost, and are suitable for mass production.

When used as an electrode for a battery, it is preferable that the carbon electrode is impregnated with and / or supported by a battery active material.

Electrodes made of small-diameter carbon fibers and / or carbon fiber fragments are electrochemically stable, so even if they are impregnated with a solution containing a battery active material and used with the battery active material carried, they can be overcharged and discharged. On the other hand, it shows excellent durability.

Further, the carbon electrode has a large hydrogen overvoltage, and even if charging / discharging is performed at a high current density, the Coulomb efficiency does not decrease.

In the present invention, the width of the electrode chamber between the multipolar partition plate and the diaphragm is 0.5 to 2 mm. Further, the height of the electrode chamber is preferably in the range of 100 to 500 mm.

In the present invention, if the active state (electrode reactivity) of the carbon felt surface is about the same as the conventional one, the bulk density of the carbon felt may be 20 to 30%, and the flow resistance (viscosity) of the active material liquid is 10 mPa · sec. If it is less than the degree, the head loss of the active material liquid due to the circulation in the carbon felt can be suppressed to a small value.
The apparent linear velocity is a value obtained by dividing the amount of the active material liquid sent by the cross-sectional area of the electrode chamber. The volume change of the electrode chamber due to carbon felt filling is ignored.

Next, in the present invention, the active material liquid is used in the electrolytic cell (positive electrode cell or negative electrode cell) because the apparent linear velocity when the active material liquid flows through the cell is in the range of 3 to 7 cm / sec. It is possible to reduce the liquid feeding pressure, which is the pump pressure when sending the liquid to the water, by about 50%, and there is an effect that a secondary battery capable of high input / output can be provided.
In general, the larger the electrode area of a cell and the larger the number of stacked cells, the lower the equal distribution in cells and the equal distribution between cells of the active material liquid. At this time, the uniformity of the carbon felt in the electrode chamber (uniform flow resistance) is very important. However, the amount of carbon felt (bulk density) usually varies by more than 10 to 20%, and the flow resistance of the active material liquid when it permeates the carbon felt causes the electrodes to be more equidistant than ensuring equality between cells. It is preferable to ensure equal distribution by the flow resistance of the electrolyte slit between the chamber and the manifold.
Therefore, rather, it is preferable to reduce the basis weight of carbon felt, ensure equal distribution without increasing the liquid feed pressure, and further increase the liquid feed amount (linear velocity) to reduce the area resistivity. ..

Next, a preferred embodiment of the active material liquid (electrolytic liquid) used in the present invention will be described.

In a preferred embodiment, the active material solution is contained so that the vanadium concentration is 1.2 M or more and 1.8 M or less, and the total sulfate root concentration including hydrogen sulfate root is 4 M or more and 8 M or less, and in the Raman spectrum on the high frequency side. No shoulder peak showing hydrogen bonding at 3,200 cm ^-1 was observed, and even if the shoulder peak was observed, it was 1% or less of the peak for OH at ^{3400 to 3500 cm -1.}

That is, the current density of the battery is increased by containing the vanadium concentration in the active material solution so as to be 1.2 M or more and 1.8 M or less, and the total sulfate root concentration including hydrogen sulfate root is 4 M or more and 8 M or less. be able to.

In another preferred embodiment, the active material solution is contained so that the vanadium concentration is 1.2 M or more and 1.8 M or less, and the total sulfate root concentration including hydrogen sulfate root is 4 M or more and 8 M or less, and the volume resistivity at 25 ° C. The rate is 7.0 Ωcm or less.

In another preferred embodiment, the active material solution is contained so that the vanadium concentration is 1.2 M or more and 1.8 M or less, and the total sulfate root concentration including hydrogen sulfate root is 4 M or more and 8 M or less, and the viscosity at 25 ° C. is high. It is 10 mPa · sec or less.

In the current redox flow type secondary battery having a cell stack structure, it is said that there is a problem in the uniformity of the electrodes (felt) in the cell, which greatly affects the flow resistance of the electrolytic solution. By binding thin carbon fine particles, fibers, etc. to the bipolar plate, the effect of forming a cell stack that greatly reduces the flow resistance and improves the flowability of the electrolytic solution and the like is exhibited.
When the flow resistance (viscosity) of the active material liquid is about 10 mPa · sec or less, the head loss of the active material liquid due to the circulation in the carbon felt can be suppressed to a small value.

Hereinafter, the effects of the present invention will be illustrated by examples.

(Example 1)
1. 1. Cell stack A 40-cell stack was manufactured as follows.
Resin (PVC) presser plate / multi-pole partition plate (carbon plastic sheet) / ^{carbon felt-filled electrode chamber with bulk density of about 0.2 g / cm 3} / diaphragm (thickness of about 50 μm fluorine-based ion exchange membrane) are laminated in this order. A 40-cell stack was manufactured using the above-mentioned cell.

(Cell specifications) Shape of electrode chamber of each cell of positive electrode and negative electrode Width 200 mm
Height 150mm
Thickness 0.5 mm

2. 2. Production of active material solution An active material solution having a vanadium concentration of 1.4 to 2.0 M and a total sulfate root concentration of 8 M was used.
Specifically, it is shown in Table 1.

3. 3. Charge / discharge test A charge / discharge test was performed at room temperature (about 23 ° C).

4. Liquid delivery to the cell The amount of liquid supply to the cell was adjusted by controlling the inverter of the pump.
The amount of liquid sent was measured by an ultrasonic flow meter and shown in Table 1 as the amount of liquid sent (L / min).
The liquid feed pressure was measured with a corrosion resistance gauge pressure gauge and is shown as the liquid feed gauge pressure in Table 1.

5. Test Results (1) Area resistivity The area resistivity as a single battery was calculated from the charge / discharge voltage value at ^{a current density of 200 mA / cm 2} when the charging depth of the active material liquid was about 50%, and is shown in Table 1. ..
(2) Apparent linear velocity The apparent linear velocity is shown in Table 1 as a numerical value obtained by dividing the amount of the active material liquid sent by the cross-sectional area of the electrode chamber. The volume change of the electrode chamber due to carbon felt filling is ignored.

From Table 1, when the active material solution having a vanadium concentration of 1.4 M and a total sulfate root concentration of 8 M has an apparent linear velocity in the range of 3 to 7 cm / sec when flowing through the electrode chamber, the bulk density is 0. When 2 g / cm ³ carbon felt was used, the liquid feed volume was in the range of 7.2 to 16.8 L / min, and the area resistivity was reduced to ^{0.8 to 1.6 Ωcm 2.} That is, it was also found ^{that the area resistivity decreased to 1.5 Ωcm 2} or less even when the liquid feed rate was about 5 L / min. At this time, the liquid feed gauge pressure was 0.04 to 0.09 MPa.

(Example 2)
The relationship between the battery active material liquid composition and each physical property value was investigated. The results are shown in Table 2.

(Example 3)
The relationship between the electrode chamber thickness and the area resistivity was investigated by the following experiment.
The frame (spacer) of the electrode chamber is made of a soft PVC sheet, a cell cell having a predetermined electrode chamber thickness is formed, and an active material solution having a vanadium concentration of 1.6 M and a total sulfate root concentration of 4.5 M is used. , A charge / discharge test was performed.
The results are shown in Table 3.

In this test, the limit of the amount of liquid to be sent from the pump power is 600 mL / min per cell, and the thickness of the lower two electrode chambers, which has a large area resistivity at the maximum allowable amount of liquid to be sent, gives good results. I couldn't.

(Example 4)
For active material solution used in the measurement example 1 of the Raman spectrum, the Raman spectra of the high frequency side, the hydrogen bonds shoulder peak height at 3200 cm ^-1 and (P1), the peak height related to OH of 3400~3500cm ^-1 ( The ratio of P2) was calculated.
The Raman spectrum was measured by Raman spectroscopy using a microscopic Raman spectroscopic analyzer (“NRS-5000” manufactured by JASCO Corporation).

As a result of the above measurement, it was found that P1 was not observed as shown in FIG.
Further experiments confirmed that even if P1 was confirmed, it was 1% or less of P2.

(Example 5)
Measurement of Chemical Shift Value in Proton Nuclear Magnetic Resonance Absorption Spectrum The active material solution of Example 1 was subjected to 1H-NMR spectrum measurement at a resonance frequency of 200 kHz to obtain a chemical shift in the proton nuclear magnetic resonance absorption spectrum.

It was confirmed that the value was 30 ppm or less as shown in FIG.

1 Positive electrode chamber 2 Negative electrode chamber 3 diaphragm 5 Conductive sheet 6 Presser plate 11 Positive electrode 12 Inflow port 13 Outlet 14 Positive electrode active material tank 15 Pump 16 Inflow pipe 17 Outflow pipe 21 Negative electrode 22 Inflow port 23 Outlet 24 Negative electrode active material tank 25 Pump 26 Inflow pipe 27 Outflow pipe 100 Cell stack 100A Cell 101 Cell 102 Cell 107 Cell frame member 108 Cell frame member 113 Cell internal space 114 Cell internal space 119 Diaphragm 100B Cell 103 Cell 104 Cell 109 Cell frame member 110 Cell frame member 115 Cell Internal space 116 Cell internal space 120 diaphragm 100C cell 105 cell 106 cell 111 Cell frame member 112 Cell frame member 117 Cell internal space 118 Cell internal space 121 diaphragm 122 Partition plate 123 Partition plate 124 Partition plate 125 Partition plate 128 Inflow pipe 129 Outflow pipe 130 Inflow port 131 Outlet

Claims (6)

A redox flow type in which a plurality of cell cells having an electrode chamber for performing a battery reaction are electrically stacked in series, and an active material liquid which is a battery active material can be shared among the plurality of cell cells. In the secondary battery
The width of the electrode chamber between the multi-pole partition plate and the diaphragm is 0.5 to 2 mm.
Further, a redox flow type secondary battery characterized in that the apparent linear velocity when the active material liquid flows through the electrode chamber is in the range of 3 to 7 cm / sec. The redox flow type secondary battery according to claim 1, wherein the height of the electrode chamber is in the range of 100 to 500 mm. The active material solution is contained so that the vanadium concentration is 1.2 M or more and 1.8 M or less, and the total sulfate root concentration including hydrogen sulfate root is 4 M or more and 8 M or less, and in the Raman spectrum on the high frequency side, 3200 cm ^{−. The redox flow according to claim 1 or 2, wherein the shoulder peak showing a hydrogen bond in 1} is not observed, and even if the shoulder peak is observed, it is 1% or less of the peak for OH of ^{3400 to 3500 cm -1.} Type secondary battery. The active material solution is contained so that the vanadium concentration is 1.2 M or more and 1.8 M or less, and the total sulfate root concentration including hydrogen sulfate root is 4 M or more and 8 M or less, and the chemical shift in the proton nuclear magnetic resonance absorption spectrum. The redox flow type secondary battery according to claim 1 or 2, wherein the value is 30 ppm or less (however, 0 ppm is not included). The active material solution is contained so that the vanadium concentration is 1.2 M or more and 1.8 M or less, and the total sulfate root concentration including hydrogen sulfate root is 4 M or more and 8 M or less, and the volume resistivity at 25 ° C. is 7.0 Ωcm. The redox flow type secondary battery according to claim 1 or 2 below. The active material solution is contained so that the vanadium concentration is 1.2 M or more and 1.8 M or less, and the total sulfate root concentration including hydrogen sulfate root is 4 M or more and 8 M or less, and the viscosity at 25 ° C. is 10 mPa · sec or less. The redox flow type secondary battery according to claim 1 or 2.

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