KR102379200B1 - Zinc-bromide flow battery comprising conductive interlayer - Google Patents

Abstract

The present invention relates to a zinc-bromine flow battery including a conductive intermediate layer, and to improve the zinc desorption process by reducing the amount of dendrite inactive zinc in the negative electrode, thereby improving the capacity and lifespan characteristics of the battery. A zinc-bromine flow battery according to the present invention includes a membrane, a first electrode stacked on one side around the membrane, a second electrode stacked on the other side around the membrane, and interposed between the negative electrode and the membrane among the first and second electrodes and a conductive intermediate layer having a logarithmic value of hydrogen evolution exchange current density of -4 or less under an acid-based electrolyte.

Description

Zinc-bromide flow battery comprising conductive interlayer

The present invention relates to a zinc-bromine flow battery, and more particularly, to a conductive intermediate layer capable of improving the capacity and lifespan characteristics of the battery by reducing the amount of inactive zinc in the form of dendrites in the negative electrode to improve the zinc desorption process It relates to a zinc-bromine flow battery comprising a.

The redox flow battery refers to a battery capable of electrochemically converting chemical energy of an active material into electrical energy. In such a redox flow battery, an electrolyte including an active material that causes oxidation/reduction reactions circulates between the counter electrode and the storage tank, thereby charging and discharging. The anode electrolyte generates an electric current through a redox reaction on the anode side and is stored in the anode electrolyte tank. The anode electrolyte is stored in the cathode electrolyte tank by generating an electric current through a redox reaction on the cathode side.

A redox flow battery is a secondary battery of a system in which a solution of two types of redox couple, which is an active material, reacts at an anode and a cathode. A redox flow battery is a battery that is charged and discharged by supplying a redox couple solution from the outside of the battery cell. As a redox couple, Fe/Cr, V/Br, Zn/Br, Zn/Ce, V/V, etc. are used.

When a zinc-bromine flow battery using Zn/Br as a redox couple is charged, an electrochemical reaction such as "2Br ^- → Br ₂ + 2e ^- " is formed, and bromine is produced in the anode electrolyte and stored in the anode electrolyte tank. do. At the cathode, an electrochemical reaction such as "Zn ²⁺ +2e ^- → Zn" proceeds, and zinc ions contained in the cathode electrolyte are deposited as zinc. In this process, zinc dendrites are formed at the cathode.

The zinc dendrite thus formed increases the irreversibility of the charging and discharging reactions, thereby causing a decrease in the capacity and cycle life of the battery. Also, zinc dendrites grow from the negative electrode to the positive electrode, pierce the membrane and contact the positive electrode, causing a short circuit in the battery.

Korean Patent Registration No. 10-1722153 (Registered on March 27, 2017)

Accordingly, it is an object of the present invention to provide a zinc-bromine flow battery comprising a conductive intermediate layer capable of improving the zinc desorption process by reducing the amount of inactive zinc in the form of dendrites in the negative electrode, thereby improving the capacity and lifespan characteristics of the battery is to do

In order to achieve the above object, the present invention is a membrane; a first electrode stacked on one side of the membrane; a second electrode stacked on the other side of the membrane; and a conductive intermediate layer interposed between the negative electrode and the membrane among the first and second electrodes, and having a log value of hydrogen generation exchange current density of -4 or less under an acid-based electrolyte; zinc-bromine flow battery comprising a.

The conductive intermediate layer has an electrical conductivity of 1 S/cm or more at room temperature.

The conductive intermediate layer is made of a metal or carbon material.

The metal material includes Ti, Zn, or SUS.

The carbon material includes carbon nanotubes, graphene, or graphite.

In the zinc-bromine flow battery according to the present invention, the zinc desorption capacity after the initial 5 driving is 150% or less of the discharging capacity at the time of the previous driving.

The zinc-bromine flow battery according to the present invention may have a driving current density of 1 to 100 mA/cm ² , and a current density during detachment is 1/4 or less of the driving current density.

The conductive intermediate layer has the form of a fiber sheet, foam or mesh.

And the present invention provides a membrane, a first electrode and a second electrode disposed to face each other with the membrane interposed therebetween, respectively coupled to the first electrode and the second electrode to flow an electrolyte solution to the first and second electrodes a plurality of unit cells stacked with first and second flow frames; and a plurality of bipolar plates interposed between the plurality of unit cells and stacked on both sides of the plurality of stacked unit cells. In this case, the unit cell includes a conductive intermediate layer interposed between the negative electrode and the membrane among the first and second electrodes, and having a log value of hydrogen generation exchange current density of -4 or less in an acid-based electrolyte.

According to the present invention, by forming a conductive intermediate layer having electrical conductivity between the negative electrode and the membrane, the effect of increasing the reaction area of the negative electrode and improving the distribution of the electrolyte between the negative electrode and the membrane, It is possible to reduce the amount of zinc and improve the capacity and lifespan characteristics of the battery.

That is, the conductive intermediate layer increases the active area at the negative electrode as well as increases the active area due to the even distribution of the electrolyte, thereby reducing the current density, thereby reducing the formation of inactive zinc dendrites during the charging process, and improving the charging and discharging efficiency characteristics. Thus, a high-performance zinc-bromine flow battery can be realized.

1 is a view showing a zinc-bromine flow battery having one unit cell according to the present invention.
2 is a view showing a zinc-bromine flow battery having a plurality of unit cells according to the present invention.
3 is a graph of measuring the zinc desorption capacity of the zinc-bromine flow battery according to Comparative Examples and Examples.
4 is a graph measuring the desorption capacity of zinc after 5 cycles of charging and discharging of a zinc-bromine flow battery according to a comparative example.
5 is a graph measuring the desorption capacity of zinc after 5 cycles of charging and discharging of the zinc-bromine flow battery according to the embodiment.
6 is a graph of measuring the efficiency characteristics of a zinc-bromine flow battery according to a comparative example when driven at a current density of 40 mA/cm ² .
7 is a graph of measuring the efficiency characteristics of the zinc-bromine flow battery according to the embodiment when driven at a current density of 40 mA/cm ² .

It should be noted that, in the following description, only the parts necessary for understanding the embodiments of the present invention will be described, and descriptions of other parts will be omitted in the scope not disturbing the gist of the present invention.

The terms or words used in the present specification and claims described below should not be construed as being limited to their ordinary or dictionary meanings, and the inventors have appropriate concepts of terms to describe their invention in the best way. It should be interpreted as meaning and concept consistent with the technical idea of the present invention based on the principle that it can be defined in Accordingly, the embodiments described in this specification and the configurations shown in the drawings are only preferred embodiments of the present invention, and do not represent all of the technical spirit of the present invention, so various equivalents that can be substituted for them at the time of the present application It should be understood that there may be variations and variations.

Hereinafter, embodiments of the present invention will be described in more detail with reference to the accompanying drawings.

1 is a view showing a zinc-bromine flow battery having one unit cell according to the present invention.

Referring to FIG. 1 , a zinc-bromine flow battery 100 according to the present invention has a membrane 11, a first electrode 13 stacked on one side with the membrane 11 as the center, and the membrane 11 on the other side. The second electrode 15 stacked on the side and the first and second electrodes 13 and 15 are interposed between the negative electrode and the membrane 11, and the log value of the hydrogen generation exchange current density under the acid-based electrolyte is -4 The following conductive intermediate layer 30 is included. Here, the acid-based electrolyte may be 1M H ₂ SO ₄ .

The zinc-bromine flow battery 100 according to the present invention includes a unit cell 10 and a pair of bipolar plates 61 and 69 bonded to both sides of the unit cell 10, and a pair of bipolar plates First and second current collectors 71 and 79, first and second cell frames 81 and 89, and first and second electrolyte tanks 91 and 96 sequentially installed on the outside of (61, 69) , the first and second pumps 92 and 97 may be further included.

The unit cell 10 includes a membrane 11 , a first electrode 13 , a second electrode 15 , a conductive intermediate layer 30 , a first flow frame 20 , and a second flow frame 50 . The first electrode 13 and the second electrode 15 are disposed to face each other with the membrane 11 interposed therebetween. The first and second flow frames 20 and 50 are respectively coupled to the first electrode 13 and the second electrode 15 to flow the electrolyte to the first and second electrodes 15 . The first electrode 13 and the second electrode 15 are electrodes having opposite polarities. For example, the first electrode 13 may be an anode, and the second electrode 15 may be a cathode. The conductive intermediate layer 30 is interposed between the second electrode 15 and the membrane 11 .

In this case, the membrane 11 serves to separate the first electrolyte and the second electrolyte during charging or discharging, and selectively moving only ions during charging or discharging. Such a membrane 11 is not particularly limited to a commonly used one.

The first and second electrodes 13 and 15 provide active sites for oxidation/reduction of the first and second electrolytes, respectively. Carbon material electrodes may be used as the first and second electrodes 13 and 15 . For example, activated carbon, graphite, hard carbon, or porous carbon material may be used as a material of the first and second electrodes 13 and 15, but is not limited thereto. The porous carbon material includes carbon felt, carbon cloth or carbon paper. Preferably, for the first and second electrodes 13 and 15, carbon felt or carbon paper may be used as a carbon material.

The conductive intermediate layer 30 is formed under an acid-based electrolyte to improve the distribution of the electrolyte between the second electrode 15 and the membrane 11 as well as to increase the reaction area of the second electrode 15, which is the negative electrode. The log value of the hydrogen generation exchange current density is -4 or less, and it has an electrical conductivity of 1 S/cm or more at room temperature. The conductive intermediate layer 30 may be made of a metal or carbon material. For example, the metal material includes, but is not limited to, Ti, Zn, or SUS. The carbon material includes, but is not limited to, carbon nanotubes, graphene, or graphite.

The conductive intermediate layer 30 may be implemented in the form of a fiber sheet, foam, or mesh, but is not limited thereto.

As such, the conductive intermediate layer 30 has the effect of increasing the reaction area of the second electrode 15 and improves the distribution of electrolyte between the second electrode 15 and the membrane 11, thereby It is possible to reduce the amount of zinc and improve the capacity and lifespan characteristics of the battery.

That is, the conductive intermediate layer 30 not only increases the effect of increasing the activity due to the even distribution of the electrolyte, but also increases the active area in the second electrode 15 to reduce the current density, thereby reducing the formation of inactive zinc dendrites during the charging process and , the charging and discharging efficiency characteristics can be improved. The conductive interlayer 30 also improves energy density and reversibility.

In addition, the first and second flow frames 20 and 50 have a first electrode insertion hole 27 and a second electrode insertion hole 57 into which the first electrode 13 and the second electrode 15 are inserted, respectively. each is formed. The first and second flow frames 20 and 50 apply the first electrolyte and the second electrolyte to the first and second electrodes 13 and 15 inserted into the first and second electrode insertion holes 27 and 57, respectively. It includes a flow path, which is a passage for flow. A plastic resin such as polyethylene (PE), polypropylene (PP), polystyrene (PS), or vinyl chloride (PVC) may be used as a material of the first and second flow frames 20 and 50, and is limited thereto it is not

In the zinc-bromine flow battery 100 , a ZnBr ₂ aqueous solution is used as the first electrolyte and the second electrolyte, and complexing agents for suppressing the generation of bromine in the ZnBr ₂ aqueous solution, and conductive to improve the conductivity of the electrolyte Additives such as agents may be included. As an additive, ZnCl ₂ , quaternary ammonium bromide (QBr), etc. may be used. For example, as an electrolyte, an electrolyte in which ZnCl ₂ , QBr is added to a 2-3M ZnBr ₂ aqueous solution may be used.

A pair of bipolar plates 61 and 69 are stacked on the outside of the first and second flow frames 20 and 50 . A conductive plate may be used as the bipolar plates 61 and 69 . A conductive graphite plate may be used as a material of the bipolar plates 61 and 69 . For example, the bipolar plates 61 and 69 may be graphite plates impregnated with phenol resin. When the graphite plate is used alone as the bipolar plates 61 and 69, the strong acid used in the electrolyte may permeate the graphite plate. Therefore, as the bipolar plates 61 and 69, it is preferable to use a graphite plate impregnated with a phenol resin to prevent the permeation of strong acids.

At this time, in the first electrode 13 inserted into the first electrode insertion hole 27 of the first flow frame 20 , the first electrode 13 exposed to the outside through the first electrode insertion hole 27 , Both sides contact the membrane 11 and the bipolar plates 61 and 69, respectively. In order to prevent the first electrolyte from leaking through the interface between the membrane 11, the first flow frame 20 and the bipolar plates 61 and 69, between the membrane 11 and the first flow frame 20, or A gasket may be interposed between the first flow frame 20 and the bipolar plate 61 .

In addition, in the second electrode 15 inserted into the second electrode insertion hole 57 of the second flow frame 50 , the second electrode 15 exposed to the outside through the second electrode insertion hole 57 , Both sides contact the membrane 11 and the bipolar plates 61 and 69, respectively. In order to prevent the second electrolyte from leaking through the interface between the membrane 11, the second flow frame 50 and the bipolar plates 61 and 69, between the membrane 11 and the second flow frame 50, or A gasket may be interposed between the second flow frame 50 and the bipolar plates 61 and 69 .

First and second current collectors 71 and 79 are stacked on the outside of the pair of bipolar plates 61 and 69 . The first and second current collectors 71 and 79 are passages through which electrons move, and serve to receive electrons from the outside during charging or to give out electrons to the outside during discharging. As the first and second current collectors 71 and 79, a conductive metal plate made of copper or brass may be used.

The first and second cell frames 81 and 89 are coupled to the outside of the first and second current collectors 71 and 79 . The first and second cell frames 81 and 89 fix the unit cell 10 interposed therebetween, a pair of bipolar plates 61 and 69 , and the first and second current collectors 71 and 79 . The first and second cell frames 81 and 89 have an inlet and an outlet for injecting or flowing out the first and second electrolytes into the first and second flow frames 20 and 50 of the unit cell 10, respectively, there is. An insulator may be used as a material of the first and second cell frames 81 and 89 . For example, as a material of the first and second cell frames 81 and 89, polyethylene (PE), polypropylene (PP), polystyrene (PS), or vinyl chloride (PVC) may be used, but is not limited thereto.

The first electrolyte tank 91 has a first inlet pipe 93 and a first outlet pipe 94 connected to an inlet and an outlet formed in the first cell frame 81, respectively, to supply the first electrolyte to the first cell frame 81. ) is cycled. At this time, a first pump 92 for circulating the first electrolyte is connected to the first inlet pipe 93 .

And the second electrolyte tank 96 is connected to the second inlet pipe 98 and the second outlet pipe 99 respectively to the inlet and outlet formed in the second cell frames (81, 89), respectively, the second electrolyte to the second cell cycle to frame 89 . At this time, a second pump 97 for circulating the second electrolyte is connected to the second inlet pipe 98 .

The zinc-bromine flow battery 100 according to the present invention circulates the first and second electrolytes as follows. That is, the first electrolyte drawn from the first electrolyte tank 91 is injected into the inlet of the first cell frame 81 through the first inlet pipe 93 by the operation of the first pump 92 . The first electrolyte injected into the inlet of the first cell frame 81 passes through the first current collector 71 and the first bipolar plate 61 through the first flow frame 20 of the unit cell 10 . It passes through the electrode 13 . And the first electrolyte passing through the first electrode 13 is the first flow frame 20, the first bipolar plate 61, the second current collector 79 and the first through the outlets of the cell frame 81 1 It flows out through the outlet pipe (94). And the first electrolyte discharged through the first outlet pipe 94 enters the first electrolyte tank 91 .

And the second electrolyte withdrawn from the second electrolyte tank 96 is injected into the inlet of the second cell frame 89 through the second inlet pipe 98 by the operation of the second pump 97 . The second electrolyte injected into the inlet of the second cell frame 89 passes through the second current collector 79 and the second bipolar plate 69 through the second flow frame 50 of the unit cell 10 . It passes through the electrode 15 . And the second electrolyte passing through the second electrode 15 is the second flow frame 50, the second bipolar plate 69, the second current collector 79 and the second through the outlets of the cell frame 89 2 flows out through the outlet pipe (99). And the second electrolyte discharged through the second outlet pipe 99 enters the second electrolyte tank 96 .

In the zinc-bromine flow battery 100 according to the present invention as described above, the zinc desorption capacity after the initial 5 driving is 150% or less of the discharge capacity at the time of the immediately preceding driving. And the zinc-bromine flow battery 100 according to the present invention may have a driving current density of 1 to 100 mA/cm ² , and a current density during detachment is 1/4 or less of the driving current density.

Meanwhile, in FIG. 1 , an example in which the zinc-bromine flow battery 100 includes one unit cell 10 is disclosed, but the present invention is not limited thereto. That is, as shown in FIG. 2 , the zinc-bromine flow battery 200 may have a structure in which a plurality of unit cells 10 are stacked.

2 is a view showing a zinc-bromine flow battery 200 having a plurality of unit cells 10 according to the present invention.

Referring to FIG. 2 , in the zinc-bromine flow battery 200 , a bipolar plate 60 is respectively interposed between a plurality of unit cells 10 , and a pair of bipolar plates on both sides of the stacked plurality of unit cells 10 . Except for the structure in which the plate 60 is disposed, the zinc-bromine flow battery 100 of FIG. 1 has the same structure. That is, the zinc-bromine flow battery 200 includes first and second current collectors 71 and 79, a first and second current collectors 71 and 79 on a pair of bipolar plates 61 and 69 positioned on both sides of the stacked plurality of unit cells 10 . The first and second cell frames 81 and 89 and the first and second electrolyte tanks 91 and 96 are connected.

Meanwhile, although the zinc-bromine flow battery 200 according to FIG. 2 discloses an example in which three unit cells 10 are stacked, the present invention is not limited thereto. That is, a zinc-bromine flow battery can be implemented by stacking two or more unit cells 10 .

In order to confirm the performance of the zinc-bromine flow battery including the conductive intermediate layer 30 according to the present invention, zinc-bromine flow batteries according to Comparative Examples and Examples were prepared and electrochemical characteristics were evaluated.

A carbon paper electrode was used as the anode, and a bipolar plate having a flow path was used. A carbon paper electrode was used for the negative electrode, and a bipolar plate without a flow path was used. Between the membrane and the negative electrode, a general plastic mesh (Comparative Example) and a titanium (Ti) mesh (Example) were introduced as intermediate layers, respectively. A mixed solution of 2.25M ZnBr ₂ and 3M KCl was used as the basic electrolyte.

Long-term lifespan was evaluated while the zinc desorption process was performed once every 5 cycles, and the results are shown in the graphs of FIGS. 3 to 5 . Here, FIG. 3 is a graph measuring the zinc desorption capacity of the zinc-bromine flow battery according to Comparative Examples and Examples. 4 is a graph measuring the desorption capacity of zinc after 5 cycles of charging and discharging of a zinc-bromine flow battery according to a comparative example. And FIG. 5 is a graph measuring the desorption capacity of zinc after 5 cycles of charging and discharging of the zinc-bromine flow battery according to the embodiment.

3 to 5 , it was confirmed that the zinc desorption capacity in the example in which the titanium mesh was used was decreased compared to the zinc desorption capacity in the comparative example. That is, in the case of the embodiment, the zinc desorption capacity after the initial 5 driving is 150% or less of the discharge capacity at the time of the previous driving.

By introducing the titanium mesh-based conductive interlayer in the embodiment, it was confirmed that the effect of reducing the zinc desorption capacity related to the formation of zinc dendrites was compared with the comparative example.

The results of comparing the efficiency characteristics when driving at a current density of 40 mA/cm ² by introducing the intermediate layer according to Comparative Examples and Examples are the same as in the graphs of FIGS. 6 and 7 . 6 is a graph of measuring the efficiency characteristics of a zinc-bromine flow battery according to a comparative example when driven at a current density of 40 mA/cm ² . 7 is a graph of measuring the efficiency characteristics of the zinc-bromine flow battery according to the embodiment when driven at a current density of 40 mA/cm ² .

6 and 7 , it was confirmed that the Example had an improvement effect in terms of coulombic efficiency, voltage efficiency and energy efficiency compared to the comparative example.

On the other hand, the embodiments disclosed in the present specification and drawings are merely presented as specific examples to aid understanding, and are not intended to limit the scope of the present invention. It is apparent to those of ordinary skill in the art to which the present invention pertains that other modifications based on the technical spirit of the present invention can be implemented in addition to the embodiments disclosed herein.

10: unit cell
11: membrane
13: first electrode
15: second electrode
20: first flow frame
27: first electrode insertion hole
30: conductive intermediate layer
50: second flow frame
57: second electrode insertion hole
61: first bipolar plate
69: second bipolar plate
71: first current collector
79: second current collector
81: first cell frame
89: second cell frame
91: first electrolyte tank
92: first pump
93: first inlet pipe
94: first outlet pipe
96: second electrolyte tank
97: second pump
98: second inlet pipe
99: second outlet pipe
100, 200: zinc-bromine flow battery

Claims (11)

membrane;
a first electrode stacked on one side of the membrane;
a second electrode stacked on the other side of the membrane; and
A conductive intermediate layer interposed between the negative electrode and the membrane among the first and second electrodes and having a log value of hydrogen generation exchange current density of -4 or less in an acid-based electrolyte;
The material of the negative electrode is a carbon material,
The material of the conductive intermediate layer is a metal material, and the conductive intermediate layer is a zinc-bromine flow battery, characterized in that it has the form of a fiber sheet, foam or mesh. According to claim 1,
The conductive intermediate layer is a zinc-bromine flow battery, characterized in that it has an electrical conductivity of 1 S / cm or more at room temperature. 3. The method of claim 2,
The material of the negative electrode is a zinc-bromine flow battery, characterized in that activated carbon, graphite, hard carbon or porous carbon material. 4. The method of claim 3,
Zinc-bromine flow battery, characterized in that the metal material comprises Ti, Zn or SUS. 5. The method of claim 4,
Zinc-bromine flow battery, characterized in that the zinc desorption capacity after the initial 5 driving is 150% or less of the discharge capacity at the time of the previous driving. 6. The method of claim 5,
A zinc-bromine flow battery, characterized in that the driving current density can be selected from 1 to 100 mA/cm ² , and the current density at the time of detachment is 1/4 or less of the driving current density. delete Membrane, first and second electrodes disposed to face each other with the membrane interposed therebetween, first and second coupled to the first and second electrodes, respectively, to flow an electrolyte to the first and second electrodes a plurality of unit cells stacked with a flow frame; and
a plurality of bipolar plates interposed between the plurality of unit cells and stacked on both sides of the plurality of stacked unit cells;
The unit cell is
A conductive intermediate layer interposed between the negative electrode and the membrane among the first and second electrodes and having a log value of hydrogen generation exchange current density of -4 or less in an acid-based electrolyte;
The material of the negative electrode is a carbon material,
The material of the conductive intermediate layer is a metal material, and the conductive intermediate layer is a zinc-bromine flow battery, characterized in that it has the form of a fiber sheet, foam or mesh. 9. The method of claim 8,
The conductive intermediate layer is a zinc-bromine flow battery, characterized in that it has an electrical conductivity of 1 S / cm or more at room temperature. delete 10. The method of claim 9,
Zinc-bromine flow battery, characterized in that the zinc desorption capacity after the initial 5 driving is 150% or less of the discharge capacity at the time of the previous driving.

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