KR101934570B1 - Redox flow battery - Google Patents

Abstract

The redox flow cell according to the present invention comprises a stack for generating a current, an anode electrolytic cell for storing an anode electrolytic solution supplied through a first pipe to the stack, an anode electrolytic cell connected to a first connection pipe and a second connection pipe, And a two-phase electrolytic cell for storing the cathode electrolytic solution discharged from the stack through a third pipe, wherein the first connecting pipe and the second connecting pipe are connected to each other The first connection pipe provides a flow path through which the gas flows between the anode electrolytic cell and the cathode electrolytic cell and the second connection pipe connects the anode electrolytic cell and the cathode electrolytic cell to the cathode electrolytic cell, Lt; / RTI >

Description

Redox Flow Battery {REDOX FLOW BATTERY}

The present invention relates to redox flow cells.

The redox flow cell is an energy storage system that stores the generated power in a grid and supplies it at the required time to increase energy efficiency.

A redox flow cell is a stack comprising a bipolar electrode and a membrane which are repeatedly laminated, a laminate of a current collector plate and an end cap laminated on both sides of the outermost layer, and an electrolyte solution is supplied to the stack And an electrolyte tank for storing an electrolytic solution flowing out after the internal reaction in the stack.

The electrolyte contains an active material, which enables oxidation and reduction of the active material to enable charging and discharging, and is an important factor determining the capacity of the battery.

Among them, the electrolyte of the zinc / bromine flow cell is composed of zinc ions and bromide ions. In the case of bromide ions, bromine is converted to bromine at the time of charging. Since the solubility of bromine is low, it can easily be vaporized and lost. As a result, the amount of the reactant is reduced to deteriorate performance, or there is a safety risk. In order to compensate for this, the bromine complex is formed by introducing a bromine complex to increase the solubility of bromine, thereby preventing loss of bromine and ensuring stability.

However, by forming a bromine complex, the viscosity increases and changes the flowability and affects the internal pressure. Also, in the case of zinc ions, the zinc ions are applied to the electrodes at the time of charging to narrow the gap between the channels, thereby changing the internal pressure, thereby causing a crossover phenomenon.

In addition, since the electrolytic solution moves to one electrolytic cell, the reaction is not uniform due to the difference in the level of the electrolytic solution, and thus the reaction material can not be supplied to each electrode, shortening the life of the electrode.

Accordingly, the present invention provides a redox flow cell capable of uniformly maintaining the internal pressure between the anode electrolytic cell and the cathode electrolytic cell and reducing the difference in water level between the anode electrolytic cell and the cathode electrolytic cell, thereby increasing the life of the electrode uniformly .

The present invention also provides a redox-flow battery in which an electrolyte is not left on the bottom of an electrolytic cell when the electrolytic solution is discharged from the electrolytic bath.

According to an aspect of the present invention, there is provided a redox flow cell comprising: a stack for generating a current; an anode electrolytic cell storing an anode electrolytic solution supplied through a first pipe to the stack; A cathode electrolytic cell connected to the stack through a second pipe and storing a cathode electrolytic solution supplied through the second pipe; and a two-phase electrolytic cell storing the cathode electrolytic solution discharged from the stack through a third pipe, Wherein the second connecting pipe is located at a different height and the first connecting pipe provides a flow path through which the gas between the anode electrolytic bath and the cathode electrolytic bath is moved and the second connecting pipe is connected to the cathode electrolytic bath, Thereby providing a flow path through which the electrolytic solution moves.

The first connecting pipe is located at a first height from the bottom of the anode electrolyzer and the second connecting pipe is located at a second height from the bottom of the anode electrolyzer and the first height is higher than the second height at the top of the anode electrolyzer Can be positioned adjacent.

Wherein the first height is a height of a water surface of the electrolyte that is initially filled in the anode electrolyzer and the cathode electrolyzer and the second height is an anode electrolyzer in which the anode electrolytic bath and the electrolytic solution first filled in the cathode electrolytic bath are stored through the stack once, And may be an average water surface height of the cathode electrolyzer.

And a control valve provided in each of the first pipe and the second pipe, wherein the control valve includes a pressure sensor for measuring the internal pressure of the first pipe and the second pipe, and a ratio valve connected to the pressure sensor can do.

The bottom of the anode electrolyzer, the cathode electrolyzer, and the two-phase electrolyzer may include an inclined surface inclined toward the pipe and the second pipe so that the anode electrolytic solution and the cathode electrolytic solution flow through the first pipe and the second pipe.

And an overflow pipe installed between the cathode electrolyzer and the two-phase electrolyzer.

One side of the overflow tube may be located closer to the bottom of the cathode electrolyzer than the second height.

As described in the present invention, by manufacturing the redox flow cell, uniform pressure is maintained between the anode electrolytic cell and the cathode electrolytic cell while maintaining a uniform water level, thereby preventing the reaction from proceeding unevenly.

Therefore, the electrode life of the redox-flow battery can be increased.

1 is a schematic block diagram of a redox flow cell according to an embodiment of the present invention.
Figure 2 is an exploded perspective view of the stack applied to Figure 1;
3 is a cross-sectional view taken along line III-III in FIG.
4 is a cross-sectional view taken along the line IV-IV in Fig.
5 is a schematic cross-sectional view of the electrolyzer applied to Fig.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings, which will be readily apparent to those skilled in the art to which the present invention pertains. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein.

In order to clearly illustrate the present invention, parts not related to the description are omitted, and the same or similar components are denoted by the same reference numerals throughout the specification.

It is to be understood that both the foregoing general description and the following detailed description of the present invention are exemplary and explanatory and are intended to provide further explanation of the invention as claimed. In the following detailed description, the names of components are categorized into the first, second, and so on in order to distinguish them from each other in the same relationship, and are not necessarily limited to the order in the following description. Throughout the specification, when a component is referred to as "comprising ", it means that it can include other components as well, without excluding other components unless specifically stated otherwise. The term " unit ", "unit "," part ", "member ", and the like refer to a unit of a comprehensive configuration that performs at least one function or operation.

Hereinafter, a redox flow cell according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a schematic configuration diagram of a redox flow cell according to an embodiment of the present invention, FIG. 2 is an exploded perspective view of the stack applied to FIG. 1, and FIG. 3 is a cross- Fig. 4 is a cross-sectional view cut along the line IV-IV in Fig. 2, and Fig. 5 is a schematic cross-sectional view of the electrolyzer applied to Fig.

1 and 2, a redox flow battery according to an embodiment of the present invention includes a stack 100, an electrolytic solution supplying unit 110 for supplying an electrolyte solution to the stack 100, And a circulation unit for connecting the electrolytic baths 200, 300, 400 and the electrolytic baths 200, 300, 400 to the stack 100.

The stack 100 may be connected to external charges through the bus bars B1 and B2 to discharge the current generated inside the stack 100. [

For example, the stack 100 can be formed by stacking a plurality of unit cells C1 and C2. For convenience of explanation, in the embodiment of the present invention, the first unit cell C1 and the second unit cell C2 located on both the left and right sides will be described as an example.

3 and 4, the stack 100 includes a membrane 10, a spacer 20, an electrode plate 30, a membrane flow frame 40, an electrode flow frame 50, a first current collector plate 61 A second current collecting plate 62, a first end cap 71, and a second end cap 72. The first end cap 62 and the second end cap 62 are electrically connected to each other.

Since the stack 100 has a plurality of unit cells C1 and C2, the two membrane flow frames 50, which are disposed at the center of the electrode flow frame 50 and are arranged in a symmetrical structure on both sides of the electrode flow frame 50, And a pair of first end caps 71 and second end caps 72, which are disposed on the outer periphery of the membrane flow frame 40, respectively.

The membrane 10 is configured to pass ions and is coupled to the center of the membrane flow frame 40 in the thickness direction, and the electrode plate 30 is coupled to the center in the thickness direction of the electrode flow frame.

The first end cap 71, the membrane flow frame 40, the electrode flow frame 50, the membrane flow frame 40 and the second end cap 72 are disposed and the membrane 10 and the electrode plate 30 The plurality of unit cells C1 to C2 are formed by bonding the membrane flow frame 40, the electrode flow frame 50 and the first and second end caps 71 and 72 to each other with the spacers 20 interposed therebetween. The stack 100 is formed.

The electrode plates 61 and 62 are formed such that the anode electrode 32 is formed on one side and the cathode electrode 31 is formed on the other side in the portion where the plurality of unit cells C1 and C2 are connected to form a plurality of unit cells C1 And C2 are connected in series to form a bipolar electrode. A carbon coating layer may be formed on the cathode electrode 31.

The membrane flow frame 40, the electrode flow frame 50 and the first end cap 71 are adhered to each other to set the internal volume S between the membrane 10 and the electrode plate 30, A first flow channel CH1 and a second flow channel CH2 for supplying an electrolyte solution to the first flow channel CH1 and the second flow channel CH2 are formed. The first flow channel CH1 and the second flow channel CH2 are configured to supply the electrolytic solution to both sides of the membrane 10 at a uniform pressure and amount, respectively.

The first channel channel CH1 connects the anode electrolyte solution inlet H21 and the internal volume S and the anode electrolyte solution outlet H22 so that the membrane 10 and the anode electrode 32 ) To allow the electrolyte to flow out after reaction with the anode electrolyte.

The second flow channel CH 2 connects the cathode electrolyte inlet H 31, the internal volume S and the cathode electrolyte outlet H 32 so that the membrane 10 and the cathode electrode 31 to allow the cathode electrolytic solution to flow out after the reaction.

The membrane flow frame 40, the electrode flow frame 50, the first end cap 71, and the second end cap 72 are made of an electrically insulating material including a synthetic resin component, .

The flow cell according to the present invention may be a zinc-bromine flow battery. During charging, a reaction as shown in [Equation 1] occurs between the membrane 10 and the cathode electrode 31, (2) may occur between the first electrode 32 and the second electrode.

 [Formula 1]

2Br ^- > 2Br + 2e ^-

[Formula 2]

Zn ^{2 +} + 2e ^- → Zn

Conversely, during the discharge, a reverse reaction of [Equation 1] occurs between the membrane 10 and the cathode electrode 31, and an adverse reaction of [Equation 2] occurs between the membrane 10 and the anode electrode 32.

The first current collecting plate 61 and the second current collecting plate 62 collect current generated in the cathode electrode 31 and the anode electrode 32 or collect the current generated in the cathode electrode 31 and the anode electrode 32 And may be electrically connected to the outermost electrode plate 30 by bonding.

The first bus bar B1 and the second bus bar B2 are electrically connected to the first current collecting plate 61 and the second current collecting plate 62, Lt; RTI ID = 0.0 > 100 < / RTI >

The first end cap 71 receives a first current collecting plate 61 connected to the first bus bar B1 and an electrode plate 30 connected to the first current collecting plate 61, . The first end cap 71 may be integrally formed with the first current collecting plate 61 and the electrode plate 30 of the bus bar B1 and may be integrally formed with the first current collecting plate 61, The plate 30 can be inserted and molded by insert injection.

The second end cap 72 includes a second current collecting plate 62 connected to the second bus bar B2 and an electrode plate 30 connected to the second current collecting plate 62, Can be formed. The second end cap 72 may be formed by insert injection by inserting the second bus bar B2, the second current collector plate 62, and the electrode plate 30. FIG.

The first end cap 71 has anode and cathode electrolyte inlets H21 and H31 on one side and is connected to the first and second flow channels CH1 and CH2 so as to introduce the anode electrolyte and the cathode electrolyte respectively. The second end cap 72 has anode and cathode electrolyte outlets H22 and H32 on one side and is connected to the first and second flow channels CH1 and CH2 to discharge the anode electrolyte and the cathode electrolyte.

1 and 2, the anode electrolytic bath 200 supplies an anode electrolytic solution between the membrane 10 and the anode electrode 32 of the stack 100, and between the membrane 10 and the anode electrode 32 And the anode electrolyte solution flows out through the anode. The anode electrolyte may be an electrolytic solution containing zinc.

The cathode electrolyzer 300 supplies a cathode electrolytic solution between the membrane 10 and the cathode electrode 31 of the stack 100. The catholyte may be an electrolytic solution containing bromine.

The two-phase electrolytic bath 400 accommodates a cathode electrolytic solution (two-phase electrolytic solution) flowing out between the membrane 10 and the cathode electrode 31 of the stack 100. The electrolytic solution of the two-phase electrolytic bath 400 can be separated into two phases depending on the specific gravity by the cathode electrolytic solution flowing out between the membrane 10 and the cathode 31. Of these, the middle dibromin is located at the bottom of the two-phase electrolyzer and the aqueous bromine is located at the top of the two-phase electrolyzer.

The two-phase electrolytic bath 400 may be connected to the cathode electrolytic bath 200 via an orb flow pipe (not shown), and the aqueous bromine located above the two-phase electrolytic bath 400 may be connected to the cathode electrolytic bath 300 ). ≪ / RTI > At this time, one end of the overflow pipe located in the cathode electrolytic bath 300 may be disposed adjacent to the water surface of the cathode electrolyzer 300, or may be disposed so as to be submerged in the water surface to minimize the generation of air bubbles in the electrolytic solution due to the falling of the electrolytic solution .

Referring to FIG. 5, a first connection pipe L51 and a second connection pipe L52 may be provided between the anode electrolytic cell 200 and the cathode electrolytic cell 300. Valves V1 and V2 are provided in the first connection pipe L51 and the second connection pipe 52, respectively.

The first connection pipe L51 provides a gas flow path through which the gas generated from the anode electrolytic bath 200 and the cathode electrolytic bath 300 is moved and the internal pressure of the anode electrolytic bath 200 and the cathode electrolytic bath 300 This balance is achieved.

The second connection pipe L52 is provided to compensate for the difference in the level of the electrolytic solution between the anode electrolyzer 200 and the cathode electrolyzer 300. When the electrolytic water level of any one of the electrolytic baths is high, The electrolytic solution moves by the water pressure, and the electrolytic solution in the anode electrolytic bath 200 and the cathode electrolytic bath 300 can maintain the same level of water level.

The first connection pipe L51 and the second connection pipe L52 may be located at different heights and may be installed at the first height H1 and the second height H2, respectively. The first height H1 may be located closer to the top of the anode 200 than the second height H2.

The first height H1 is the level of the anode electrolyte and the cathode electrolyte initially filled.

When the anode electrolyte of the first height H1 and the cathode whole liquid pass through the stack 100, the electrolyte remains in the stack 100 or remains in the circulation portion to fill the anode electrolytic bath 200 and the cathode electrolytic bath 300 The water level of the electrolytic solution may be lowered, and the water level becomes lower than the first height H1.

The anode electrolytic solution and the cathode electrolytic solution that have passed through the stack 100 flow into the anode electrolytic bath 200 and the two-phase electrolytic bath 400, respectively. Thereafter, the electrolytic solution overflowing from the two-phase electrolytic bath 400 is moved to the cathode electrolytic bath 300 through the orifu pipe 201.

Accordingly, the water level of the anode electrolytic bath 200 is higher than the water level of the cathode electrolytic bath 200, so that the water level difference may occur. At this time, when the valve V2 of the second connection pipe L52 is opened, the electrolytic solution of the anode electrolytic bath 200 at a relatively high position is moved to the cathode electrolytic bath 300 of a relatively low position and the anode electrolytic bath 200 and the cathode The water level of the electrolytic bath 300 becomes equal.

Accordingly, the second height H2 is the same as the average water surface of the anode electrolyte and the cathode electrolyte, which is filled after the initially filled anode electrolyte and cathode electrolyte circulate in the stack 100. [

The bottom surfaces of the anode electrolyzer 200, the cathode electrolyzer 300 and the two-phase electrolytic bath 400 include inclined surfaces SD that are inclined toward the side walls of the electrolyzer.

The stack 100 and the electrolytic cells 200, 300 and 400 may be connected to the circulation unit and the anode electrolytic solution and the cathode electrolytic solution may circulate the stack 100 and the electrolytic cells 200, 300 and 400 through the circulation unit.

Referring again to FIGS. 1 and 2, the circulation unit may include a plurality of pipes L21, L22, L31, L32, and L41 and pumps P1 and P2. An anode outlet H22 of the anode electrolyzer 200 and the anode outlet H22 of the stack are connected to a second pipe L22, The electrolytic bath 300 is connected to the cathode inlet H31 of the stack by a third pipe L31 and the cathode outlet H32 and the two-phase electrolytic bath 400 are connected to each other through a fourth pipe L32. At this time, the first pump L21 and the third pipe L31 may be provided with a first pump P1 and a second pump P2, respectively, and may be supplied to the first and second pumps P1 and P2 The electrolytic solution can be controlled by the control valves VV1 and VV2.

The third pipe L31 connecting the cathode electrolyzer 300 and the cathode inlet H31 may further include a branch pipe L41 branched from the branch pipe and connected to the two-phase electrolytic bath 400. [ The branch pipe L1 may be provided with a valve V3.

Meanwhile, the bottom of the electrolyzer according to an embodiment of the present invention includes the inclined surface SD, and the inclined surface SD can be tilted so that the electrolytic solution can flow toward the first pipe L21 and the third pipe L31 have. When the inclined plane SD is formed, the electrolyte moves along the inclined plane SD, so that it can be easily transferred to the pipe, so that the electrolyte remaining on the bottom of the electrolyzer can be minimized. The inclined plane can be inclined at an inclination angle? Of 10 degrees or more with respect to a virtual plane perpendicular to the electrolytic cell side wall.

In addition, control valves VV1, VV2, VV3, and VV4 may be installed in the first pipe to the fourth pipe, respectively. The control valves VV1, VV2, VV3, and VV4 include a pressure sensor and a ratio valve for sensing the pressure in the pipe, and the pressure sensor and the ratio valve can be connected to the control unit 700. [ The control unit 700 receives the measured pressure information from the pressure sensor, and determines the degree of opening of the rate valve according to the pressure to control the rate valve.

That is, the pressures of the first pipe and the third pipe are high, the pressures of the second pipe and the fourth pipe are low, and a pressure difference is generated therebetween, so that the pressure inside the stack may not be uniform. As described above, if a pressure difference occurs between a portion where the electrolyte is injected and a portion where the electrolyte is injected, the electrical characteristics of the battery may be reduced.

Accordingly, if the measured pressure is high, the ratio valve is opened to reduce the pressure, and if the pressure is low, the ratio valve is tightened to increase the pressure so that the pressure difference between the first pipe and the second pipe, Can be adjusted so that the pressure difference of the first and second pressure chambers does not occur. Of course, it is possible to reduce the pressure difference by increasing or decreasing the voltage of the first pump and the second pump and changing the flow rate of the electrolytic solution.

Comparison of energy efficiency and charge efficiency

The electrode was made of carbon plastic (manufactured by Lotte Chemical Co., Ltd.) to have a thickness of 600 mu m, and the membrane was manufactured by Asahi product name SF601 to have a thickness of 600 mu m.

Energy efficiency, voltage efficiency, and charge efficiency can be obtained from Equation 3, Equation 4, and Equation 5, respectively.

[Formula 3]

Energy Efficiency (EE) = (discharge energy (Wh) / charge energy (Wh)) * 100

[Formula 4]

Voltage Efficiency (VE) = (energy efficiency / charge efficiency) * 100

[Formula 5]

Current Efficiency (CE) = (Discharging Capacity (Ah) / Charging Capacity (Ah)) * 100

[Comparative Example]

Energy efficiency, voltage efficiency and charge efficiency were measured during 10 cycle charge / discharge.

cCycle efficiency[ % ] energy Voltage Charge quantity One 71.0 79.8 88.9 2 72.2 79.3 91.1 3 71.5 79.1 90.5 4 71.4 79.0 90.4 5 71.3 79.0 90.3 6 69.9 79.5 87.9 7 71.2 79.0 90.1 8 70.5 78.8 89.5 9 70.3 78.7 89.4 10 70.2 78.7 89.3

Referring to Table 1, it can be seen that the energy efficiency, the voltage efficiency and the charge efficiency decrease as the charge / discharge progresses, and the reduction in the charge efficiency is large.

[Example]

After 5 cycles charging / discharging, the second connecting pipe was opened immediately after discharging to regulate the water level, and the charge / discharge proceeded.

cycle Presence or absence of second connection pipe efficiency(%) energy Voltage Charge quantity One

has exist

71.9 79.9 89.9 2 73.1 79.4 92.1 3 72.4 79.2 91.5 4 72.3 79.1 91.4 5 72.2 79.1 91.3 balancing 6

has exist

71.7 79.7 90.0 7 73.7 80.1 92.0 8 72.3 79.0 91.5 9 72.3 79.1 91.5 10 72.0 79.0 91.2

Referring to Table 2, the second connection pipe was opened to move the electrolytic solution to maintain the electrolyte level between the anode electrolyzer and the cathode electrolyzer at the same level. Thereafter, it can be confirmed that the energy efficiency, the voltage efficiency, and the charge efficiency are maintained or decreased, while the charge and discharge are progressed. This is because the irregularity of the ion supply caused by the crossover is solved and the discharge charge amount is increased to prevent the energy efficiency from being lowered.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, but, on the contrary, And it goes without saying that the invention belongs to the scope of the invention.

10: membrane 20: spacer
30: electrode plate 31: cathode electrode
32: anode electrode 40: membrane flow frame
50: electrode flow frame 61, 62: first and second collectors
71, 72: first and second end caps 100: stack
200: anode electrolyzer 300: cathode electrolyzer
400: Two phase electrolyzer

Claims (6)

A stack generating current,
An anode electrolytic cell storing an anode electrolytic solution supplied through the first pipe to the stack,
A cathode electrolytic cell connected to the anode electrolytic cell, the first connection pipe and the second connection pipe, for storing the cathode electrolytic solution supplied through the second pipe to the stack,
A two-phase electrolytic bath for storing the cathode electrolytic solution discharged through the third pipe in the stack,
An overflow pipe installed between the cathode electrolytic cell and the two-phase electrolytic cell,
/ RTI >
Wherein the first connecting pipe and the second connecting pipe are located at different heights,
The first connection pipe provides a flow path through which gas between the anode electrolyzer and the cathode electrolyzer moves,
Wherein the second connection pipe provides a flow path through which the electrolyte flows according to a difference in water level between the anode electrolyzer and the cathode electrolyzer,
Wherein one side of the overflow pipe is located at the same height as one side of the first connecting pipe,
Wherein the other side of the overflow pipe is the same as one side of the second connecting pipe or is located closer to the bottom of the two-phase electrolytic cell than one side of the second connecting pipe. The method of claim 1,
Wherein the first connecting pipe is located at a first height from the bottom of the anode electrolyzer,
The second connecting pipe is located at a second height from the bottom of the anode electrolyzer,
Wherein the first height is located closer to the top of the anode electrolyzer than the second height. 3. The method of claim 2,
Wherein the first height is a height of a water surface of an electrolyte first filled in the anode electrolyzer and the cathode electrolyzer,
Wherein the second height is an average water surface height of the anode electrolytic cell and the cathode electrolytic cell, through which the electrolytic solution initially filled in the anode electrolytic cell and the cathode electrolytic cell passes through the stack once. The method of claim 1,
Wherein the bottom of the anode electrolyzer, the cathode electrolyzer, and the two-phase electrolyzer includes an inclined surface inclined toward the first pipe and the second pipe so that the anode electrolytic solution and the cathode electrolytic solution flow into the first pipe and the second pipe Redox flow cell. delete 3. The method of claim 2,
Wherein one side of the overflow tube is positioned closer to the bottom of the cathode electrolyzer than the second height.

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