KR20090046087A - A separator structure and redox flow battery containing the separator membrane - Google Patents

Abstract

The present invention relates to a separator structure for a redox flow battery having a porous polymer membrane attached to both sides of an ion exchange membrane, and a redox flow battery including the separator structure.

Such a membrane structure attaches a porous polymer membrane to both sides of the ion exchange membrane to improve mechanical strength, which is a weak point of a thin ion exchange membrane, and thus is applied to a redox flow battery, thereby reducing the pressure difference generated in the flow of electrolyte. In addition to reducing the direct impact on the ion exchange membrane, battery life and efficiency can be improved, as well as protection of the electrolyte separator that distinguishes the positive and negative electrodes without increasing the internal resistance of the cell and prevention of cell short circuits.

Redox flow battery, ion exchange membrane, separator, porous polymer membrane, housing cell

Description

Redox flow battery comprising a separator structure for a redox flow battery and the separator structure {A separator structure and redox flow battery containing the separator membrane}

The present invention relates to the structure of the separator used in the redox flow battery, and more particularly, in the redox flow battery, the mechanical strength of the ion exchange membrane which distinguishes the positive and negative electrolytes from mixing and only allows the passage of ions. It relates to a separator structure and a redox flow battery comprising the separator structure capable of improving.

In modern society, the battery industry has also developed remarkably, depending on the high growth of the electric and electronic fields. In particular, it is possible not only to convert electrical energy into chemical energy and store it, but also to convert it into electrical energy and use it as a breakthrough. Through the improvement of the secondary battery that can use a high capacity of electricity in small and light battery has been actively developed.

These secondary batteries have been used in a variety of applications such as small mobiles, medium and large-sized ups and power storage as high-efficiency energy storage systems, and are used in semiconductors and liquid crystals, acoustics such as audio, mobile phones, PDAs, Not only has been used as a key core component in the field of information and communication, such as notebooks, but also as a fuel cell of an environmentally friendly hybrid electric vehicle, the application to load leveling, etc. in combination with a battery is being actively progressed.

As described above, secondary batteries used in various applications are required to develop a more stable energy supply and high efficiency energy conversion system, and thus, redox as a high capacity and high efficiency secondary battery that is most suitable for a large-sized system such as power storage. Redox flow batteries are in the spotlight.

Unlike other batteries, such a redox flow battery has a mechanism for storing an active material as ions in an aqueous solution rather than a solid state and storing energy by oxidation / reduction reactions of respective ions at the cathode and the anode.

1 is a view schematically showing a conventional redox flow battery.

As shown therein, the cell housing 1 having a predetermined size is separated by an ion exchange membrane 10 installed across the center thereof, and left of the cell housing 1 separated as described above. The positive electrode 21 and the negative electrode 22 are located at both sides of the right side, respectively, and the upper and lower ends of the cell housing 1 have inlets 31 and 32 and outlets 41 and 42 of the electrolyte used for the respective electrode reactions. Is formed.

At this time, the charge and discharge occurs as the positive and negative electrolytes (catholyte) and the negative electrolyte (anolyte) stored in the tank separately mounted to the outside of the cell housing (1), the positive and negative electrolytes are ion exchange membrane (10) It is separated from each other by to prevent the mixing between the electrolyte solution, and only the transfer of ions is allowed, it is circulated while flowing along the electrolyte passage of the laminated battery or unit cell of each electrode during charging and discharging.

Such a redox flow battery is discharged by connecting an electrical load to an external circuit including an electrical load and allowing a current to flow therein, and conversely, charging is performed by connecting an external power source to the battery to allow a current to flow therein.

In general, a catholyte is charged when the redox couple is oxidized to the higher of the two valence states, and discharges when the redox couple is reduced to the lower of the two valence states. Conversely, an anode electrolyte is charged when the redox couple is reduced to the lower of the two valence states, and is discharged when the redox couple is oxidized to the higher of the two valence states.

Such a cathode electrolyte and a cathode electrolyte have a flow mode battery system circulated into a cell through a pump outside of an electrolyte tank, whereas an electrolyte solution is impregnated in an electrode and left standing inside a cell to operate without circulating the electrolyte. It can also be used as a batch mode battery system.

On the other hand, the redox flow battery as described above requires the use of a thinner ion exchange membrane to increase the output, the thinner the ion exchange membrane has a problem that the mechanical strength is lowered, while maintaining the mechanical strength There is an urgent need to study the structure of the separator that can be reduced in thickness. When the thickness of the ion exchange membrane was about 100 μm or less, the membrane was often broken during cell manufacture.

In addition, the reaction of the electrolyte in the redox flow battery is different from the positive electrode and the negative electrode, the pressure difference occurs in the positive electrode side and the negative electrode side as the flow of the electrolyte is present, this pressure difference affects the physical properties of the intermediate ion exchange membrane Since it adversely affects the life and efficiency of the battery, there is also a way to solve this problem.

Therefore, the present invention is configured to solve the above problems, by attaching a chemically stable porous polymer membrane to the ion exchange membrane used as a component of the redox flow battery to increase the mechanical strength of the ion exchange membrane and An object of the present invention is to provide a separator structure capable of suppressing deterioration of an ion exchange membrane.

In addition, another object of the present invention is to provide a redox flow battery comprising a structure of a membrane separating an ion exchange membrane having a porous polymer membrane as described above.

The present invention to achieve the above object,

It is achieved by providing a separator structure for a redox flow battery, characterized in that a porous polymer membrane is attached to both sides of the ion exchange membrane in a sandwich form.

In addition, in the above-described separator structure, the polymer membrane is a film or non-woven fabric of polyethylene (PE), polypropylene (PP), polyvinyl difluoride (PVdF), polyacrylonitrile (PAN) -based polymer material It provides a separator structure for a redox flow battery, characterized in that it is manufactured in the form of a felt (felt).

In addition, the present invention is an ion exchange membrane installed across the center of the cell housing, the anode and cathode are respectively located inside the cell housing separated by the ion exchange membrane, the image of the cell housing. In the redox flow battery is formed for each electrode at each end and the inlet and outlet to perform the inflow and outflow of the electrolyte used for each electrode, characterized in that the porous polymer membrane is attached to both sides of the ion exchange membrane Provided is a redox flow battery.

In the redox flow battery described above, the present invention uses a V (IV) / V (V) redox couple as a cathode electrolyte and a V (II) / V (III) redox couple as a cathode electrolyte. It provides a redox flow battery, which is an all-vanadium redox flow battery.

In the redox flow battery described above, the present invention is an all-vanadium redox flow battery using a halogen redox couple as a cathode electrolyte and a V (II) / V (III) redox couple as a cathode electrolyte. Provided is a redox flow battery.

In addition, the present invention, in the above-described redox flow battery, it is a polysulfide bromine (PSB) redox flow battery using a redox couple as a cathode electrolyte and a sulfide redox couple as a cathode electrolyte. A redox flow battery is provided.

In addition, the present invention is a zinc-bromine (Zn-Br) redox flow battery using a halogen redox couple as the cathode electrolyte, and a zinc (Zn) redox couple as the cathode electrolyte in the above-described redox flow battery It provides a redox flow battery, characterized in that.

In addition, the present invention is a redox flow laminated battery in which a plurality of bipolar plates are connected in series, and a cation exchange membrane and an anion exchange membrane are alternately disposed between the bipolar plates, wherein the cation exchange membrane and the anion exchange membrane are sandwiched at both sides. It provides a redox flow laminated battery characterized in that the separator structure is applied with a porous polymer membrane attached.

As described above, the separator structure for a redox flow battery of the present invention attaches a porous polymer membrane to both sides of the ion exchange membrane to improve mechanical strength, which is a weak point of the ion exchange membrane having a thin thickness, and improves the pressure difference generated by the flow phenomenon of the electrolyte. In addition to improving the life and output characteristics of the battery by directly reducing the influence on the exchange membrane 10, the protection of the electrolyte separator that distinguishes the positive electrode and the negative electrode without increasing the internal resistance of the cell and the prevention of a short circuit of the cell can be prevented. It can be effective.

Hereinafter, the present invention will be described in detail with reference to the embodiments shown in the accompanying drawings, but the present invention is not limited to the embodiments shown in the drawings.

2 is a view schematically showing a redox flow battery having a separator structure of the present invention.

As shown therein, the separator structure of the present invention is left in contact with both sides of the ion exchange membrane 10, i.e., the positive and negative electrolytes. Sandwich type on the right side is characterized in that the porous polymer membrane (51, 52) is attached. The adhesion of the porous polymer membrane as described above is easily achieved by impregnating it with an aqueous electrolyte solution or pure distilled water due to the property of the membrane having good wettability. In some cases, a small amount of polymeric binder may be used at the four corners and at the center of the ion exchange membrane for adhesion.

The porous polymer membranes 51 and 52 reinforce mechanical strength inevitably falling when the thickness of the ion exchange membrane 10 is reduced for high output, and thus sufficiently express the strength in the ion exchange membrane 10 and at the same time the outer surface thereof. In this case, the pressure difference generated in the flow of different electrolytes in the positive electrode and the negative electrode when used in the battery is directly reduced on the ion exchange membrane 10 to improve the life and efficiency of the battery. Can be.

Examples of the porous polymer membranes 51 and 52 used as described above include polyethylene (PE), polypropylene (PP), polyvinyl difluoride (PVdF), and polyacrylonitrile (PAN) -based polymer materials such as films, nonwoven fabrics, It is used in the form of a felt (felt) or the like, the pore size of the polymer membrane (51, 52) is not limited because the ionic size is different depending on the electrolyte used, but will not interfere with the movement of the electrolyte It is desirable to have a degree of size.

In the above-described separator structure, the thickness of the porous polymer membranes 51 and 52 is preferably 5 μm to 50 μm, and thus the ion exchange membrane 10 may have sufficient mechanical strength even if its thickness is 25 μm to 125 μm. This can significantly reduce the thickness compared to the ion-exchange membrane conventionally had a thickness of 125um or more.

As the ion exchange membrane 10 to which the polymer membranes 51 and 52 are attached, a Nafion cation exchange membrane used in a conventional redox flow battery is preferable, but a cation exchange membrane or an ammonium group having a sulfonic acid group or a carboxylic acid group or It is a technique applicable to both the anion exchange membrane which has a phosphonium group.

Meanwhile, as the porous polymer membranes 51 and 52 are attached to the ion exchange membrane 10, leakage of the electrolyte may occur due to separation from the cell housing 1. Thus, the porous polymer membranes 51 and 52 may be separated from each other. A gasket (not shown) may be used between the cell housings 1, and a detailed description thereof will be omitted since it is a technique commonly used in the art for sealing and preventing leakage.

In addition, the present invention provides a redox flow battery including a separator structure having sandwiched porous polymer membranes 51 and 52 attached to both sides of the ion exchange membrane 10 as described above.

As shown in FIG. 2, a cell housing 1 having a predetermined size as a component thereof, and a porous polymer membrane 51 and 52 are attached to both sides of the cell housing 1 having a predetermined size. An inner seat of the ion exchange membrane 10 and the separated cell housing 1 of the ion exchange membrane 10. An image of the cell housing 1 and the positive electrode 21 and the negative electrode 22 positioned on both sides thereof. Inlets 31 and 32 and outlets 41 and 42 which are formed at the stage and perform inflow and outflow of the electrolyte solution used for the respective electrodes are provided. The positive electrode 21 and the negative electrode 22 include carbon felt, carbon nonwoven fabric, graphite felt, graphite plate, and the like, which are conventional materials.

The reaction mechanism of the redox flow battery is formed by the oxidation / reduction reaction of the positive electrode 21 and the negative electrode 22, and the positive electrode electrolyte and the negative electrode electrolyte for causing the above reaction are stored in separate storage tanks (not shown). Stored in the cell housing 1 and introduced into the cell housing 1 through the electrolyte inlets 31 and 32 formed in the cell housing 1 to contact the positive electrode 21 and the negative electrode 22 to cause a reaction. It has a circulation system that flows out through the electrolyte outlet (41, 42).

The redox flow battery of the present invention having the above-described configuration uses V (IV) / V (V) redox couple as the cathode electrolyte and V (II) / V (III) redox couple as the cathode electrolyte. It can be applied to all-vanadium redox flow battery.

In addition, the redox flow battery of the present invention having the configuration described above uses a halogen redox couple as the cathode electrolyte, and an all-vanadium redox flow using the V (II) / V (III) redox couple as the cathode electrolyte. It can be applied to a battery.

In addition, the redox flow battery of the present invention having the configuration as described above is a polysulfide bromine (PSB) redox flow battery using a halogen redox couple as a cathode electrolyte, and a sulfide redox couple as a cathode electrolyte Can be applied to

In addition, the redox flow battery of the present invention having the configuration described above uses a halogen redox couple as a cathode electrolyte, and zinc-bromine (Zn-Br) redox using a zinc (Zn) redox couple as a cathode electrolyte. It can be applied to the flow battery.

In addition, the separator structure having sandwiched porous polymer membranes 51 and 52 attached to both sides of the ion exchange membrane 10 of the present invention may be applied to a redox flow stacked battery connected in series by a single cell and a bipolar plate.

3 is a view showing briefly applied to the laminated battery having a separator structure of the present invention.

As shown therein, a plurality of bipolar plates (B) are connected in series, and a separator structure (M) in which a sandwich-type porous polymer membrane is attached to both sides of an ion exchange membrane by a cation exchange membrane or an anion exchange membrane between the bipolar plates (B). ) Shows a redox flow stacked battery applied. Unexplained reference numerals (E1) and (E2) indicate a cathode electrolyte and a cathode electrolyte, respectively, and (P1) and (P2) indicate an electrolyte pump, respectively.

That is, the separator structure of the present invention is applicable to both the circulation mode and the batch mode of the redox flow battery system, and is particularly applicable to not only a stacked battery (stack cell in a stack module unit) but also a unit cell.

Hereinafter, the present invention will be described in more detail with reference to the following examples, which are only presented to aid the understanding of the present invention, but the present invention is not limited thereto.

Example 1

Cut Nafion into 45mmx60mm horizontally and vertically, put it in 3% hydrogen peroxide water, heat it to 100 ° C for 1 hour, cool it to room temperature and wash it with distilled water to make an ion-exchange membrane. The porous polyethylene / polypropylene polymer membrane (Celgard 3501) was attached to prepare a separator. In this case, the prepared membrane was made of one porous polymer membrane having a thickness of 25 μm and the ion exchange membrane having a thickness of 180 μm.

As described above, an ion exchange membrane having polymer membranes attached to both surfaces thereof was mounted in a test cell manufactured as shown in FIG. 1, graphite graphite was used as an electrode, and the impedance characteristics of the electrolyte were measured to analyze resistance characteristics of the separator. The results are shown in Figure 4 attached.

In addition, as a comparative example, even for a separator formed of a Nafion ion exchange membrane having a thickness of only 180 μm without a polymer membrane attached thereto, resistance characteristics were measured in the same manner under the same conditions, and the results are shown in FIG. 4.

Figure 4 is a graph showing the impedance measurement results for the ion exchange membrane according to an embodiment of the present invention, (a) is a measurement result for the separator consisting of only the ion exchange membrane as a comparative example, (b) is a porous of the present invention It shows the measurement results for the separator attached to the polymer film on both sides.

As can be seen from the measurement result of FIG. 4, in the case of (a) using the ion exchange membrane alone, the Rs value was 0.19 and the Rp value was 0.38, but the ion exchange membrane with the polymer membrane according to the present invention was used (b). In the case of Rs value is 0.21 and Rp value is 0.37, which indicates that the polymer membrane of the present invention is about 1.3 times thicker than the comparative example by the thickness, but there is no significant increase in resistance. If the thickness of is the same, there is no increase in resistance, there is an increase in mechanical strength due to the porous polymer membrane has a positive effect on the life characteristics of the cell.

In addition, since there is no increase in resistance by the porous polymer membrane, it can be seen that the resistance decreases when the thickness of the ion exchange membrane is reduced and the substitution by the porous polymer membrane. Considering that the Rs value is determined by the ion exchange membrane in the same electrolyte solution, it is obvious that the thinner the thickness of the same type of ion exchange membrane, the lower the resistance. Therefore, when using the separator designed in the present invention having the same thickness of the separator has the effect of reducing the resistance of the cell to increase the output.

1 is a view schematically showing a conventional redox flow battery

2 is a schematic view of a redox flow battery having a separator structure according to the present invention.

3 is a view briefly applied to a laminated battery having a separator structure of the present invention.

Figure 4 is a graph showing the impedance measurement results for the ion exchange membrane according to an embodiment of the present invention

<Detailed description of the major symbols in the drawings>

1: Cell Housing

  10: ion exchange membrane

  21: anode 22: cathode

  31: anode electrolyte inlet 32: cathode electrolyte inlet

  41: anode electrolyte outlet 42: cathode electrolyte outlet

  51,52: Porous polymer membrane

Claims (8)

Separator structure for a redox flow battery, characterized in that the porous polymer membrane is attached to both sides of the ion exchange membrane in a sandwich form. The method of claim 1, wherein the polymer membrane is polyethylene (PE), polypropylene (PP), polyvinyl difluoride (PVdF), polyacrylonitrile (PAN) -based polymer material or a mixture thereof is a porous film, nonwoven fabric, felt ( Separator structure for a redox flow battery, characterized in that it is manufactured in the form of (felt). An ion exchange membrane disposed across the center of the cell housing, an anode and a cathode positioned inside the cell housing separated by the ion exchange membrane, and an image of the cell housing. In the redox flow battery which is formed for each electrode in the stage and each inlet and outlet for performing the inflow and outflow of the electrolyte used for each electrode, Redox flow battery, characterized in that the separator structure of claim 1 or 2 is applied to both sides of the ion exchange membrane is attached to the porous polymer membrane. The vanadium-based redox battery according to claim 3, wherein V (IV) / V (V) redox couple is used as the cathode electrolyte and V (II) / V (III) redox couple is used as the cathode electrolyte. Redox flow battery made. The redox flow battery according to claim 3, wherein the halogen redox couple is used as the positive electrolyte and the vanadium redox battery is used using the V (II) / V (III) redox couple as the negative electrolyte. The redox flow battery according to claim 3, wherein the redox flow battery is a polysulfide bromine (PSB) redox battery using a halogen as a cathode electrolyte and a redox couple as a cathode electrolyte. The redox flow battery according to claim 3, which is a zinc-bromine (Zn-Br) redox battery using a halogen redox couple as a cathode electrolyte and a zinc (Zn) redox couple as a cathode electrolyte. In a redox flow stacked battery in which a plurality of bipolar plates are connected in series, and a cation exchange membrane and an anion exchange membrane are alternately disposed between the bipolar plates. The cation exchange membrane and the anion exchange membrane is a redox flow laminated battery, characterized in that the separator structure of claim 1 or 2, wherein a sandwich type porous polymer membrane is attached to both sides.

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