KR102004865B1 - Method for real-time monitoring of the electrolyte charge state of the redox flow battery during operation and redox flow battery capable of monitoring the electrolyte charge state in real time during operation - Google Patents

Abstract

The present invention relates to a method of monitoring the state of charge and discharge of electrolyte in a redox flow cell in real time during operation and a redox flow cell capable of monitoring the state of charged electrolyte in real time during operation, By measuring the voltage of the electrolyte solution and the UV-vis differential absorbance through a voltage measurement cell and / or an open circuit voltage (OCV) measurement cell and a UV-vis cell installed in the piping of the electrolyte circulation part, And a redox flow cell capable of monitoring the state of charge of electrolyte in real time during operation.
The present invention measures the differential absorbance (diff. Absorbance) using a reference solution (electrolyte itself), and has convenience in maintenance and repair. In addition, it is possible to monitor the charge / discharge status of the electrolyte in real time by measuring the voltage of the electrolyte solution and the UV-Vis differential absorbance in real time without loss of capacity of the redox flow cell and comparing it with the calibration curve. In addition, by using the voltage measurement cell, the OCV cell, and the UV-vis cell alternately or simultaneously, it is possible to verify the charging / discharging state of the electrolytic solution in comparison with the conventional technology, thereby improving the accuracy and stability.

Description

TECHNICAL FIELD [0001] The present invention relates to a redox flow cell capable of real-time monitoring of an electrolyte charge state of a redox flow cell during operation, AND REDOX FLOW BATTERY CAPABLE OF MONITORING THE ELECTROLYTE CHARGE STATE IN REAL TIME DURING OPERATION}

The present invention relates to a method of monitoring the state of charge and discharge of electrolyte in a redox flow cell in real time during operation and a redox flow cell capable of monitoring the state of charged electrolyte in real time during operation, By measuring the voltage of the electrolyte solution and the UV-vis differential absorbance through a voltage measurement cell and / or an open circuit voltage (OCV) measurement cell and a UV-vis cell installed in the piping of the electrolyte circulation part, And a redox flow cell capable of monitoring the state of charge of electrolyte in real time during operation.

Recently, the introduction of new and renewable energy has been expanding due to the problems of environmental pollution and climate change caused by the use of fossil fuels. In addition to the use of new and renewable energy, The development of an energy storage system (ESS) for use is underway.

ESS can be divided in various ways depending on the output and usage purpose. Among them, it is excellent in stability against explosion and fire, and can independently design capacity and output. In addition to renewable energy, As an electric energy storage device.

The redox flow battery (redox flow battery) is an electrochemical accumulation device that uses an oxidation / reduction reaction of an active material dissolved in an electrolyte, unlike an existing secondary battery that stores electric energy in an electrode containing an active material to be. The redox flow battery converts the electrical energy input through the charging process into chemical energy and stores it, and converts the chemical energy into electric energy through the discharging process.

However, in the redox flow battery, an electrode active material exists in a liquid state rather than a solid state, and an energy deviation (charge / discharge state) occurs due to movement of the active material from a tank storing an electrode active material through a pump to a stack portion serving as an output . In addition, due to the migration of the electrolyte through the ion exchange membrane of the redox flow battery, the side reaction due to the inter-cell resistance and the overcharge, the amount of the electrolyte between the electrodes, the water charge and the charged state of the electrolyte are different, Capacity, re-balancing time, etc., becomes difficult to accurately monitor and control the redox flow battery system.

Therefore, it is necessary to efficiently manage the stack through information on anode and cathode electrolytes in order to operate a stable redox flow battery over a long period of time. Accurate information on the state of charge of the electrolyte is required for such efficient management. However, in the conventional electrolyte analysis method using the OCV cell and the UV-vis absorption wavelength and the redox titration method, it is impossible to obtain accurate information on the electrolyte of the redox flow cell or to perform real-time monitoring during operation have.

Firstly, there is a limit to obtaining a precise state of the electrolytic solution in the method of checking the state of the electrolytic solution by measuring the voltage with the OCV cell, which is the most commonly used currently, such as the prior art (KR10-2015-0018148). The OCV cell has components of a typical flow cell and can measure the voltage, but since the voltage does not exactly coincide linearly with the state of the electrolyte (eg, SOC), it is not accurate to determine the SOC of the electrolyte by voltage measurement alone. The state of charging and discharging of the electrolyte can not be confirmed. In addition, the voltage measurement due to the deterioration of the OCV cell causes an error.

As a second method, there is a method of collecting an electrolyte sample, pretreating it, and measuring the state of the electrolyte through UV / Vis absorbance measurement or redox titration. However, in such a method, it is necessary to collect the electrolyte solution to check the state of the electrolyte solution, and it is troublesome to conduct the absorbance analysis by diluting the electrolytic solution with a dilute solution from the outside, and it is difficult to measure in real time. When such a method is used, it is impossible to check the state of the electrolyte in real time during the charging / discharging process, and the capacity of the battery is reduced in the process of collecting the electrolyte sample.

Korean Patent Publication No. 10-2015-0018148

The present invention relates to a method and apparatus for measuring the state of charge (SOC), state of discharge (SOD), and discharge state (SOC) of an electrolytic solution by measuring the voltage of the electrolytic solution and the differential UV- SOD = 1 - SOC) can be monitored in real time.

The present invention relates to a method for monitoring the electrolyte status of a redox-flow battery, comprising the steps of: measuring the voltage of an anode and a cathode electrolyte (step a); And measuring the UV-vis differential absorbance of the positive and negative electrode electrolytes (step b).

And comparing the measured values of step a and step b to confirm the charge / discharge state of the battery (step c).

The step b may be performed by measuring the differential absorbance of the electrolyte flowing after the charge and discharge by holding the electrolyte before the redox flow cell is driven by a reference (blank, blank).

The step (a) may be performed by a voltage measurement cell which is installed in a pipe of the electrolyte circulation part and which measures the voltage of the electrolyte solution on the anode and cathode sides, and an OCV measurement cell.

The step b may be carried out using a quartz cell for UV-vis transmission.

The electrolytic solution may be prepared by adding a pentavalent vanadium electrolytic solution prepared by an electrolytic reduction method to a tetravalent vanadium electrolytic solution.

Generally, when measuring the absorbance of a sample solution, a blank (blank) should be prepared. Blank is a solution with no absorbent and must be made identical to the sample solution except for the absorbent. This is because the absorbance curve of the blank can be subtracted from the absorbance curve of the sample solution containing the light absorbing substance so that only the peak of the light absorbing substance is emitted.

The reference of the UV-vis differential absorbance measured in real time is that the actual used electrolyte is measured from the outside and applied to the actual operation system or the absorbance wavelength value measured by using the electrolyte which is charged and discharged inside is used as a reference . In the present invention, a reference value can be obtained by measuring the differential absorbance of an electrolytic solution prepared by adding a pentavalent vanadium electrolytic solution produced by an electrolytic reduction method to a tetravalent vanadium electrolytic solution. The UV-vis differential absorbance can be measured using an ultraviolet-visible (UV-vis) spectrophotometer. The UV-vis spectrophotometer for differential absorbance measurement can be used both for wavelength scanning and for simultaneous measurement of the field, but for short time measurement and real-time electrolyte condition monitoring, UV-vis spectroscopy A photometer is preferred. The differential absorbance measurement is advantageous in that the electrolytic solution after the measurement is returned to the electrolyte tank or the electrolytic solution pipe without changing the concentration of the electrolytic solution.

As a reference spectrum for measuring the differential absorbance, a spectrum of an electrolyte (for example, water + sulfuric acid + vanadium) containing 0% SOC or 100% SOC containing an active material may be used. Calibration curves and differential absorbance measurements are taken at the wavelength of the peak spectrum appearing in the difference spectrum.

More specifically, the differential absorbance measurement method used in the present invention is a method in which an effluent (electrolytic solution) itself containing a light absorbing substance from an electrochemical reactor (for example, a redox flow cell) is injected into a blank The method of measuring the absorbance of the effluent after electrochemical reaction (charging and discharging) of the effluent after the electrochemical reaction (charging / discharging), which makes it possible to (1) separately provide the blank measuring equipment, The concentration of the vanadium ion can be measured through the measurement of the absorbance of the electrolytic solution in the present invention, and 2) the concentration of the substance (for example, sulfuric acid, additives, etc.) in the electrolyte other than vanadium, Even if an arbitrary substance is added, there is an advantage that the absorbance of vanadium alone can be obtained after the electrochemical reaction.

Conventionally, in order to obtain the absorbance value of the active material (vanadium) as in the present invention by measuring the absorbance of the blank with the supporting electrolyte (water + sulfuric acid), the absorbance value of the blank is measured separately from the outside, (Water + sulfuric acid + vanadium) containing the active material may be used after the measurement of the absorbance of the blank, and the same system may be reused after the measurement of the absorbance of the blank. In the latter method, There is a risk that the concentration can change. Alternatively, a system for the blanks and a system for the electrolytes containing the active materials must be prepared separately. That is, the system has a disadvantage that the concentration of sulfuric acid contained in the electrolytic solution including the blank and the active material must match. If the concentration of sulfuric acid in the electrolyte containing the blank and the active material is different, it is necessary to separate the peak from the absorbance value of the blank and separate the concentration of the active material.

On the other hand, according to the present invention in which the differential absorbance is measured using the electrolyte (water + sulfuric acid + vanadium) itself containing the active material as a blank, the vanadium electrolytic solution system serves as a blank before charging / discharging, , The concentration of vanadium that changes can be observed through the UV-vis cell. That is, there is no need to disassemble the system to measure the blank, and only the change in vanadium can be measured, so it is not necessary to adjust the concentration of the remaining components.

According to the present invention, when re-measurement of the reference is required according to the convenience of real-time measurement and maintenance / repair during operation, it is possible to measure directly from the installed equipment (battery) It is preferable that 100% of the electrolytic solution itself is used as a reference spectrum. This also applies to the method of creating the calibration curve.

The method is not limited to the UV-Vis measurement method, and can be applied to other optical detection methods such as Raman measurement.

More specifically, quantitative analysis using UV-Vis is based on Beer-Lambert's law. This law incorporates Lambert's law on the relationship between the distance the light travels and its absorbance, and Beer's law on the solute concentration and the environmental properties of the absorbance. Lambert's law is the law of the change in light intensity through the specimen, that is, dIz is the amount of light entering the specimen ( IZ ) and the distance dz the light passes through. Beer's law is that a molecule of solute dissolved in a solvent that does not absorb light absorbs the same fraction of light in the light passing through it, regardless of its concentration, and if applied, the proportionality constant k is the number of molecules molar concentration.

k = aC (a is a proportional constant)

The Beer-Lambert rule is established by combining the above two laws.

Combining the two expressions of the Beer-Lambert law -d z = I and the aCIzdz, it Integrating z = 0 and z = b (b = distance of light transmission), and when z = 0 z = I 0 il I, z = I, I = I (transmitted light quantity), so ln ( I ₀ / I ) = abC. I / I0 = exp (-abC). Ln ( I ₀ / I ) is the ratio of the amount of light ( I ₀ ) entering from the transmitted light ( I ) without being absorbed by the specimen when the light of a specific wavelength moves by distance b it means. The higher the concentration is lowered transmittance, absorbance A is a higher concentration as A = log10 (1 / T) = log (I / I 0) higher the absorbance.

Beer-Lambert equation: A = εbc = -logT = -log (I / I 0) = log (I 0 / I)

When the transmission distance (quartz cell size) is controlled by using the Beer-Lambert equation, the absorbance value of the high concentration vanadium used in the actual flow cell can be obtained.

The present invention also provides an ion exchange membrane comprising: an ion exchange membrane; a unit cell including an anode and a cathode located on both sides of the ion exchange membrane; A positive electrode electrolytic solution circulating unit circulating the positive electrode electrolyte so that the positive electrode electrolyte can be supplied and discharged to the positive electrode of the unit cell; And a negative electrode electrolyte circulation unit circulating the negative electrode electrolyte so that the negative electrode electrolyte can be supplied to and discharged from the negative electrode of the unit cell, wherein the redox-flow battery is installed in a pipe of the electrolyte circulation unit A UV-vis cell for measuring a voltage measurement cell (stack cell) or an open circuit voltage (OCV) measurement cell for measuring a voltage of an anode and a cathode electrolyte, and a UV-vis differential absorbance of a flowing electrolyte; And a voltage measurement cell or an open circuit voltage (OCV) measurement cell and a UV-vis cell, connected to the voltage measurement cell or the open circuit voltage (OCV) measurement cell, and the UV-vis cell, And a controller for monitoring an electrochemical state of the electrolytic solution.

The present invention also provides an ion exchange membrane comprising: an ion exchange membrane; a unit cell including an anode and a cathode located on both sides of the ion exchange membrane; A positive electrode electrolytic solution circulating unit circulating the positive electrode electrolyte so that the positive electrode electrolyte can be supplied and discharged to the positive electrode of the unit cell; And a negative electrode electrolyte circulation unit circulating the negative electrode electrolyte so that the negative electrode electrolyte can be supplied to and discharged from the negative electrode of the unit cell, wherein the redox-flow battery is installed in a pipe of the electrolyte circulation unit A UV-vis cell for measuring a voltage measurement cell (stack cell) for measuring the voltage of the electrolyte on the anode and cathode sides, an OCV measurement cell and a UV-vis differential absorbance of the flowing electrolyte; And a measurement cell connected to the voltage measurement cell, the OCV measurement cell and the UV-vis cell to analyze measurement values obtained respectively in the voltage measurement cell, the OCV measurement cell and the UV-vis cell, And a controller for monitoring the electrochemical state of the redox flow cell.

The control unit means a PC apparatus for controlling and operating the differential absorbance measurement apparatus (controlling the measuring apparatus, absorbing the absorbance, storing and calculating the absorbance).

The electrolyte solution may include vanadium, and ZnBr (Zn-Br) or the like may be used as an electrolyte solution, the optical characteristics of which vary depending on charge / discharge conditions. The electrolytic solution can be sent to a voltage measurement cell, an open circuit voltage measurement cell and a UV-vis cell through a separate small liquid transfer pump disposed in the circulation part.

The voltage measurement cell and the open circuit voltage (OCV) measurement cell may each include a voltage sensor for measuring the voltage of the electrolyte solution.

In the present invention, a voltage is measured from a stack cell in real time while a redox flow cell is operated, a voltage is measured from an OCV cell, and the voltage is measured. Then, a differential absorbance is measured with a UV-vis cell And it is estimated as the SOC or SOD value of the electrolyte and compared with the previously measured voltage, the state of the electrolyte can be accurately monitored.

More specifically, the UV-vis cell can measure the differential absorbance in real time while circulating the positive electrode electrolyte or the negative electrode electrolyte, and estimate the SOC of the electrolyte solution in real time.

The UV-vis cell may be composed of a quartz cell for UV-vis transmission, and may have a thickness of 0.05 to 10 mm, preferably a thickness of 0.5 mm or less, And may have a thickness of 0.1 mm. The thickness of the cell is the optical path length of a generally available cell, and the most common UV-vis cell has an optical distance of 10 mm. When the optical distance is larger than the above range, absorption of the UV-Vis wavelength is much absorbed and it is impossible to measure the absorbance. Since it is out of the Beer-Lambert law and it becomes difficult to use it for quantitative analysis, Lt; RTI ID = 0.0 > range. ≪ / RTI > When the absorbance value is between 0 and 1, it is well suited to the Beer-Lambert rule and is preferably 0.1 mm thick.

The present invention measures the differential absorbance (diff. Absorbance) using a reference solution (electrolyte itself), and has convenience in maintenance and repair.

In addition, it is possible to monitor the charge / discharge status of the electrolyte in real time by measuring the voltage of the electrolyte solution and the UV-Vis differential absorbance in real time without loss of capacity of the redox flow cell and comparing it with the calibration curve.

In addition, in order to overcome the disadvantage that measurement accuracy is degraded due to deterioration problem and nonlinearity of voltage measurement when OCV cell is used alone, it is also possible to use an intersection of UV-vis cells with voltage measurement cell, OCV cell, By measuring the charge / discharge state, it is possible to double verify the state of the art compared to the prior art, thereby improving the accuracy and stability.

Also, since the charging / discharging state of the electrolyte can be more accurately and quickly confirmed, the rebalancing timing can be easily predicted, so that the redox flow battery can be stably provided for a long period of time and the battery can be easily managed.

1 is a redox flow cell according to the present invention.
Figure 2 shows the structure of an open circuit voltage (OCV) cell.
3 is an algorithm for a monitoring method of an electrolyte management system for a redox flow battery.
4 is an electrolyte management system for a redox flow battery according to the present invention.
5 shows the UV-vis absorbance of the 2M VOSO ₄ in 3M H ₂ SO ₄ (V ⁴⁺ ) electrolyte according to the UV-vis cell size change.
6 (a) is a reference electrolyte prepared by mixing a pentavalent electrolytic solution having a SOC value different from that of a 4-valent vanadium electrolytic solution, wherein 0%, 1%, 2%, 3%, 4% , 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 96%, 97%, 98%, 99% 1%, 2%, 3%, 3%, and 5% by weight of a reference electrolytic solution prepared by mixing 6-fold diluted pentavalent electrolytic solution having different values of SOC in a tetravalent vanadium electrolytic solution for visual observation. 5%, 5%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 96%, 97%, 98%, 99% And a vanadium electrolytic solution are mixed.
FIG. 7 shows the results of (a) SOC and (b) time-differential UV-vis absorbance values of the anode and cathode electrolytes of the reference.
8 shows (a) the result of dQ / dV according to the calibration curve and the dQ / dV value of the UV-vis differential absorbance of the anodic electrolytic solution measured at 575 nm, DV / dV according to the SOC estimation value, and (c) the relationship between the measured voltage and the capacity in the OCV cell. Results.
9 is a graph showing the results of (a) a calibration curve showing the state of charge and discharge state of a positive electrode electrolyte measured by in-situ method at 575 nm, (b) a charge state of a negative electrode electrolyte measured by in- And the discharge state estimation value through the calibration curve. The% value in the figure means the accuracy of the experiment.

Hereinafter, the present invention will be described in more detail with reference to examples and drawings. The objects, features, and advantages of the present invention will be readily understood through the following embodiments and drawings. The present invention is not limited to the embodiments and drawings described here, but may be embodied in other forms. The embodiments described herein are provided to enable those skilled in the art to fully understand the spirit of the present invention. Therefore, the present invention should not be limited by the following examples.

According to one embodiment of the present invention, a voltage measuring cell for measuring a voltage of an electrolyte flowing in a redox flow cell, an open circuit voltage measuring cell (OCV cell), and a UV- vis cell is provided on the anode or cathode of the electrolyte or on the anode and cathode so that the voltage and the differential absorbance of the electrolyte are measured in real time during operation of the redox flow cell.

Referring to FIG. 1, a redox flow battery according to an embodiment of the present invention will now be described. A redox flow cell 100 according to an embodiment of the present invention includes a unit cell including an anode 107 and a cathode 108 with an ion exchange membrane (separation membrane) 109 interposed therebetween; A positive electrode electrolytic solution circulating unit circulating the positive electrode electrolyte so that the positive electrode electrolyte can be supplied and discharged to the positive electrode of the unit cell; And a negative electrode electrolyte circulation unit for circulating the negative electrode electrolyte solution so that the negative electrode electrolyte solution can be supplied and discharged to the negative electrode of the unit cell. In the piping of the electrolyte solution circulation unit, a voltage measuring cell 111 And a UV-vis cell (not shown) for measuring the open-circuit voltage (OCV) measurement cell 113 and the UV-vis differential absorbance of the flowing electrolyte, The cell has a voltage sensor for measuring the voltage of the positive electrode electrolyte or the negative electrode electrolyte.

 The unit cells of the present invention can be implemented in the form of stacked stack cells. The anode electrolyte circulation portion is composed of a positive electrode electrolyte tank 101, a positive electrode electrolyte pipe 103 and a positive electrode electrolyte pump 105 and is connected to the positive electrode and the negative electrode electrolyte circulation portion is also connected to the negative electrode electrolyte tank 102, And a negative electrode electrolyte pump 106 and is connected to the negative electrode.

When the anode electrolytic solution or the cathode electrolytic solution flows through the anode or cathode during the operation of the redox flow cell, the voltage of the electrolytic solution is measured in a voltage measurement cell or an open circuit voltage measurement cell installed in the anode electrolyte pipe or the cathode electrolytic solution pipe, In the -vis cell, the UV-vis differential absorbance of the electrolyte is measured. In the stack cell, since multiple manifolds are stacked, overvoltage is generated compared with a single cell, so that accurate voltage measurement becomes difficult. In addition, when SOC is measured only by a voltage value measured through a voltage measurement cell, Since the curve has a nonlinear shape, accurate SOC measurement becomes difficult. To compensate, the OCV cell is installed separately. The OCV cell 200 includes a separator 201, an anode / current collector 202, a cathode / current collector 203, flow frames 204 and 205, graphite plates 206 and 207, End plates 208 and 209 (Fig. 2). The measured values obtained from the voltage measurement cell, the open circuit voltage measurement cell and the UV-vis cell are analyzed by the control unit 114 to monitor the electrochemical state (charge / discharge state) of the anode electrolyte or the cathode electrolyte in real time, (See FIG. 3), which is a stable long-term redox flow battery, such as anticipating the rebalancing time point by confirming the side reaction, the overcharge state and the capacity reduction of the electrolyte.

Example: Establishment of electrolyte monitoring system for redox flow battery

To verify the present invention, an electrolyte management system for a redox flow battery was constructed and the differential absorbance of the electrolyte was measured. As shown in FIG. 4, the electrolyte management system for a redox flow battery is composed of an anode, a cathode, and an ion exchange membrane (separation membrane) in the same manner as a unit cell of a conventional redox flow cell. The positive electrode electrolyte circulation portion of the redox flow cell and the electrolyte piping of the negative electrode electrolyte circulation portion were connected to a voltage measurement cell (not shown), an open circuit voltage (OCV) measurement cell (shown as a test cell) and an UV- . The anode electrolytic solution circulation part and the cathode electrolytic solution circulation part circulate the electrolytic solution through a pipe by using a pump and measure the voltage of the electrolytic solution flowing by the measurement cell and the OCV measurement cell in real time And UV-vis differential absorbance was measured by irradiating the flowing electrolyte with UV-vis. The measured results can be confirmed by the charge / discharge system (control unit) of the computer. As a result of comparing the measured result with the charge / discharge result of the system, it is possible to confirm the electrochemical state of the electrolytic solution accurately and quickly compared with the conventional electrolytic solution management system I could.

Experimental Example 1: Determination of the absorbance value of the electrolyte according to the change of the UV-vis cell size

In order to confirm the UV-vis absorbance value according to the size of the UV-vis cell used in the electrolyte management system for the redox flow battery constructed in the Example, a high concentration of vanadium electrolyte used in the redox flow battery was prepared, -vis absorbance was measured. 2 M of VOSO ₄ was dissolved in 3 M sulfuric acid aqueous solution to prepare a vanadium tetravalent electrolytic solution and used in a redox flow cell. To measure the absorbance of the electrolytic solution, UV-vis cell size was adjusted to 0.05 mm, 0.1 mm, 0.5 mm.

When the absorbance value is between 0 and 1, the beer-Lambert rule is applied. As a result, it is confirmed that a reliable absorbance value is measured in a UV-vis cell having a size of 0.1 mm (FIG. 5).

Experimental Example 2: Determination of UV-vis differential absorbance change of electrolyte according to SOC (state of charge)

1, 2, 3, 4, 5, 10, 20, 30, 40, 50, 60, 70, 80, 90, and 90% in order to confirm the change of the UV-vis differential absorbance of the electrolyte according to the actual SOC. The prepared electrolytic solution was prepared by the electrolytic reduction method and then added to the tetravalent vanadium electrolytic solution to prepare a reference electrolytic solution (FIG. 6) The UV-vis spectrophotometer was used to measure the differential absorbance.

As a result of the measurement, the UV-vis differential absorbance value of all the electrolytes was measured, and the differential absorbance value was measured at various wavelengths up to 4 hours and 15 minutes (FIG. 7).

It can be confirmed that Fig. 8 (a) has a relational expression of parabola and Fig. 8 (b) has a linear relational expression. The SOC can be estimated by obtaining the remaining capacity of the UV-vis differential absorbance using the above two relations. In addition, FIG. 8 (c) is a voltage-capacitance graph measured through an OCV cell and has non-linearity, but SOC estimation can be performed using a relational expression of voltage and capacitance. 8, it was confirmed that the stability and reliability of the redox flow cell can be improved through a process of analyzing, verifying and supplementing the relationship between the UV-vis differential absorbance and the capacity / voltage and the capacity.

Referring to Table 1, as the R-square value approaches 1, the reliability is high. Therefore, the method of measuring the charging capacity through the differential absorbance in FIGS. 8 (a) and 8 (b) (DQ / dV result) is more reliable method, In addition, if the residual capacity of the battery is estimated by performing the voltage measurement and the differential absorbance measurement in parallel, the reliability can be increased.

Charge / discharge state y value R-square value Charge / discharge state y value R-square value charge Voltage 0.47 Discharge Voltage 0.72 Bipolar differential absorbance 0.99 Bipolar differential absorbance 0.99 Negative differential absorbance 0.99 Negative differential absorbance 0.98

Experimental Example 3: Confirmation of charge / discharge state of redox flow cell

In order to evaluate the charging / discharging performance of the redox flow cell, the charging upper limit voltage and the lower discharge limit voltage of the battery were set to 1.6 V and 0.8 V, respectively. The current density was set to 60 mA / cm ² , Was charged and discharged. For evaluation of charging / discharging performance, electrolytic solution having 3-valence and 4-valence oxidation states was prepared with 3 M sulfuric acid aqueous solution in 2 M VOSO ₄ , and 50 ml was injected into the anode and cathode electrolyte tanks, and the electrolytic solution was circulated using a metering pump. The flow rate of the pump was set at 8 ml / min. A voltage measurement cell, an OCV measurement cell and a 0.1 mm-size UV-vis cell were connected to the anode electrolyte circulation part and the anode electrolyte circulation part pipe, And UV-vis differential absorbance. The SOC of the electrolyte according to the differential absorbance measured by the experiment was estimated using the reference data, and the results are shown in FIG.

As a result, SOC was 80% according to the differential absorbance value measured by in-situ method at 575 nm in the positive electrode electrolyte, and when the dQ / dV data was checked, it was confirmed that the redox flow cell was not 100% charged (Fig. 9 (a)). In the negative electrode electrolyte, the SOC according to the absorbance value measured by in-situ method at 410 nm was 40 to 53%, and the SOD value was 47 to 57% (FIG. 9 (b)).

While the present invention has been particularly shown and described with reference to specific embodiments thereof, those skilled in the art will appreciate that such specific embodiments are merely preferred embodiments and that the scope of the present invention is not limited thereto will be. Accordingly, the actual scope of the present invention will be defined by the appended claims and their equivalents.

100: redox flow cell 101: anode electrolyte tank
102: cathode electrolytic solution tank 103: anode electrolytic solution piping
104: negative electrode electrolyte piping 105: positive electrode electrolyte pump
106: cathode Electrolyte pump 107: anode
108: cathode 109: ion exchange membrane (separation membrane)
111: Positive Electrolyte Voltage Measurement Cell 112: Negative Electrolyte Voltage Measurement Cell
113: Open circuit voltage (OCV) measuring cell 114:
200: OCV cell 201: OCV cell separation membrane
202: positive electrode / current collector of OCV cell 203: negative electrode / current collector of OCV cell
204: flow frame of OCV cell anode
205: flow frame of OCV cell cathode
206: graphite plate
207: graphite plate
208: End plate of OCV cell anode
209: End plate of OCV cell cathode

Claims (10)

A method for monitoring the electrolyte status of a redox flow cell,
Measuring the voltage of the anode and cathode electrolytic solution (step a);
Measuring the UV-vis differential absorbance of the anode and cathode electrolytes (step b); And
(Step c) of comparing the measured values of the step a and the step b to confirm the charging / discharging state of the battery,
Wherein the step b is performed by measuring the differential absorbance of the electrolyte flowing after the charge and discharge by holding the electrolyte before the redox flow cell including the active material to be measured as a reference,
A method for monitoring the electrolyte status of a redox flow cell.
The method according to claim 1,
Wherein the step (a) is carried out by a voltage measurement cell which is installed in a pipe of the electrolyte circulation part and which measures the voltage of the electrolyte solution on the anode and cathode sides, and an OCV measurement cell which measures the electrolyte state of the redox flow cell. How to monitor.
The method according to claim 1,
Wherein the step b is performed using a quartz cell for UV-vis transmission.
The method according to claim 1,
Wherein the electrolytic solution is prepared by adding a pentavalent vanadium electrolytic solution prepared by an electrolytic reduction method to a tetravalent vanadium electrolytic solution.
A unit cell including an ion exchange membrane and an anode and a cathode located on both sides of the ion exchange membrane;
A positive electrode electrolytic solution circulating unit circulating the positive electrode electrolyte so that the positive electrode electrolyte can be supplied and discharged to the positive electrode of the unit cell;
And a negative electrode electrolyte circulation unit circulating the negative electrode electrolyte so that the negative electrode electrolyte can be supplied and discharged to the negative electrode of the unit cell,
The redox flow battery comprises:
A stack cell or an open circuit voltage (OCV) measurement cell for measuring the voltage of the electrolyte solution on the anode and cathode sides and a UV-vis differential absorbance of the flowing electrolyte, which are provided in the piping of the electrolyte circulation part, vis cell; And
The voltage measurement cell or open circuit voltage (OCV) measurement cell and the UV-vis cell are connected to analyze the measurement values obtained respectively in the voltage measurement cell or the open circuit voltage (OCV) measurement cell and the UV-vis cell And a controller for monitoring an electrochemical state of the electrolytic solution,
Wherein the UV-vis cell measures an UV-vis differential absorbance of an electrolyte flowing in a reference by flowing an electrolyte before the redox flow cell including the active material to be measured as a reference.
A unit cell including an ion exchange membrane and an anode and a cathode located on both sides of the ion exchange membrane;
A positive electrode electrolytic solution circulating unit circulating the positive electrode electrolyte so that the positive electrode electrolyte can be supplied and discharged to the positive electrode of the unit cell;
And a negative electrode electrolyte circulation unit circulating the negative electrode electrolyte so that the negative electrode electrolyte can be supplied and discharged to the negative electrode of the unit cell,
The redox flow battery comprises:
A measurement cell (stack cell) for measuring the voltage of the electrolyte on the anode and cathode sides, an open-circuit voltage (OCV) measuring cell and a UV-vis for measuring the UV-vis differential absorbance of the flowing electrolyte Cell; And
(OCV) measurement cell and an UV-vis cell to analyze measurement values obtained respectively in a voltage measurement cell or an OCV measurement cell and a UV-vis cell, And a controller for monitoring an electrochemical state of the electrochemical cell,
Wherein the UV-vis cell measures an UV-vis differential absorbance of an electrolyte flowing in a reference by flowing an electrolyte before the redox flow cell including the active material to be measured as a reference.
◈ Claim 7 is abandoned due to registration fee. The method of claim 5,
Wherein the electrolytic solution comprises vanadium or ZnBr.
The method of claim 5,
Wherein the voltage measurement cell or the open circuit voltage (OCV) measurement cell comprises a voltage sensor for measuring the voltage of the electrolyte solution, respectively.
The method of claim 5,
Wherein the UV-vis cell comprises quartz for UV-vis transmission.
◈ Claim 10 is abandoned due to the registration fee. The method of claim 5,
Wherein the UV-vis cell has a thickness of 0.05 to 10 mm.

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