KR101568358B1 - Separator for redox flow battery and redox flow battery comprising the same - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a redox flow cell separator and a redox flow cell including the redox flow cell separator, and more particularly, to a redox flow cell separator having a constant thickness and a water content and a redox flow cell including the same. The redox flow cell separator of the present invention has a specific thickness and includes micropores having a specific average diameter and is capable of preventing direct movement of the positive electrode active material and the negative electrode active material while having excellent electric conductivity, Can be used for manufacturing.

Description

Technical Field [0001] The present invention relates to a redox flow cell separator and a redox flow cell including the redox flow cell separator.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a redox flow cell separator and a redox flow cell including the redox flow cell separator, and more particularly, to a redox flow cell separator having a constant thickness and pore and a redox flow cell including the same.

Existing power generation systems, such as thermal power generation using nuclear fossil fuels and large-scale greenhouse gas and environmental pollution problems, and nuclear power generation, which have the problems of stability of the facility itself or waste disposal problems, have various limitations and are more environmentally friendly and highly efficient Research on the development of energy and the development of power supply system using it has been greatly increased.

Particularly, the power storage technology makes it possible to utilize renewable energy which is greatly influenced by external conditions in a wider and wider range, and the efficiency of power utilization can be further increased. And research and development have been increasing.

The redox flow cell is an oxidation / reduction cell that can convert the chemical energy of the active material directly into electrical energy. It stores renewable energy with high output fluctuation depending on the external environment such as sunlight and wind power and converts it into high quality power Energy storage system. Specifically, in the redox flow cell, the electrolyte containing the active material causing the oxidation / reduction reaction circulates between the opposite electrode and the storage tank, and charging / discharging proceeds.

Such a redox flow cell basically includes a tank storing different active materials in oxidation states, a pump circulating the active material during charging / discharging, and a unit cell divided by a separator. The unit cell includes an electrode, an electrolyte, And a separator.

The separation membrane is a porous membrane containing an electrolytic solution to prevent direct contact between the electrodes in the redox flow cell to block the movement of the cathode active material and the anode active material toward the counter electrode, . However, in such a redox-flow battery, when the metal is precipitated in the anode during charging, the anode active material in the cathode electrolyte moves through the separator and the self-discharge is caused by the reaction with the deposited cathode active material, Can occur.

Accordingly, it is required to develop a separator having high electrical conductivity and excellent selective permeability to ions, which can effectively block the movement of a specific substance in the electrolyte, and which has high electrochemical and mechanical stability.

The present invention provides a redox flow cell separator which has high chemical resistance to chemical substances and can effectively block the movement of a specific substance in the electrolyte even when the electrical conductivity is high.

The present invention also provides a redox flow cell comprising the separation membrane.

The present invention comprises a polyolefin microporous membrane comprising a polyolefin resin and inorganic particles; A thickness of about 150 to about 650 mu m, and an average diameter of pores of about 20 to about 120 nm.

The present invention also provides a redox flow cell comprising the redox flow cell separator.

The redox flow cell separator of the present invention has a specific thickness and includes micropores having a specific average diameter and is capable of preventing direct movement of the positive electrode active material and the negative electrode active material while having excellent electric conductivity, Can be used for manufacturing.

1 schematically illustrates a redox flow cell according to an embodiment of the present invention.

The redox flow cell membrane of the present invention comprises a polyolefin microporous membrane comprising a polyolefin resin and inorganic particles; The thickness is from about 150 to about 650 micrometers, and the average diameter of the pores is from about 20 to about 120 nm.

In addition, the redox flow cell of the present invention includes the redox flow battery film.

The terminology used herein is for the purpose of describing exemplary embodiments only and is not intended to be limiting of the invention. The singular expressions include plural expressions unless the context clearly dictates otherwise. In this specification, the terms "comprising," "comprising," or "having ", and the like are intended to specify the presence of stated features, But do not preclude the presence or addition of one or more other features, integers, steps, components, or combinations thereof.

Also in the present invention, when referring to each layer or element being "on" or "on" each layer or element, it is meant that each layer or element is formed directly on each layer or element, Layer or element may be additionally formed between each layer, the object, and the substrate.

While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and will herein be described in detail. It should be understood, however, that the invention is not intended to be limited to the particular forms disclosed, but on the contrary, is intended to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention.

Hereinafter, the present invention will be described in more detail.

According to an aspect of the present invention, there is provided a redox flow cell separator comprising a polyolefin microporous membrane comprising a polyolefin resin and inorganic particles; The thickness is from about 150 to about 650 micrometers, and the average diameter of the pores is from about 20 to about 120 nm

Generally, a redox flow cell is a device for generating electrical energy by reacting two kinds of chemical redox couple having different oxidation numbers in an aqueous solution, respectively, at the anode and the cathode. In the redox flow cell, in contrast to the reversible change of the composition of the redox pair due to charging or discharging, only the exchange of electrons is carried out at the electrode, so there is almost no change of the electrode itself and the electrode and the active material are separated from each other However, there is a problem in that the efficiency is lowered due to the movement of the material through the separation membrane, etc. However, there is a problem in that complicated electrode reaction does not occur, the battery has a long life and the scale-up is comparatively easy.

For example, in the case of a zinc-bromodeoxane flow cell, which is a kind of zinc-halogen redox flow cell, the following reaction takes place during charging and discharging: zinc is precipitated in the anode during charging, The bromine (Br ₂ ) permeates through the separator to react with the precipitated zinc and self-discharge with ZnBr ₂ , which may reduce the efficiency.

Redox flow battery separator according to one embodiment of the present invention are zinc ions (Zn ^{2 +)} or bromide ion (Br ^-), such as species below a certain size can be selectively transmits, bromine (Br _2), such as certain The movement of the chemical species exceeding the size is effectively blocked, and the efficiency deterioration due to the self-discharge can be prevented. However, the redox flow cell separator of the present invention is not limited to the battery using the chemical species.

The redox flow cell membrane may have a thickness of about 150 to about 650 mu m, preferably about 200 to about 600 mu m. When the thickness of the redox flow cell separator is less than about 150 탆, pinhole phenomenon occurs in which mechanical strength is weak and a part of the fin separator is punctured by a metal material such as zinc precipitated when the battery is charged, If the thickness exceeds about 650 mu m, the permeation of ions through the membrane may not be efficient, and the internal resistance of the battery may become large, thereby deteriorating the performance of the battery.

In addition, the average diameter of the pores present in the redox flow cell membrane may be about 20 to about 120 nm, and preferably about 20 to about 110 nm. When the average diameter of the pores is less than about 20 nm, it is difficult to transmit ions through the membrane to increase the internal resistance of the battery, thereby deteriorating the performance of the battery. When the average diameter exceeds about 120 nm, And the performance of the battery may deteriorate due to the self-discharge phenomenon described above.

Meanwhile, the redox flow cell separator according to an aspect of the present invention includes a polyolefin microporous membrane, wherein the polyolefin microporous membrane includes a polyolefin resin and inorganic particles.

Resins used in the redox flow battery separator can be selected according to the type of the cathode active material, the anode active material, and the electrolyte used in the battery. In the case of the polyolefin resin, the cost is low and the processing to the microporous membrane is easy But also has high durability and mechanical strength against chemicals such as cathode active material, anode active material, and electrolyte, and is suitable for use as a separator of redox flow cell. The polyolefin resin is a general polyolefin resin used by ordinary extrusion, injection, inflation, blow molding and the like, and may be produced by using an ethylene-alpha olefin copolymer with polyethylene, polypropylene, or ethylene- . Examples of the comonomer used in the ethylene-alpha olefin copolymer include propylene, 1-butene, 1-pentene, 1-hexene, 1-octene, 1,3-butadiene, Hexadiene, and the like. Preferably, a polyethylene resin, a polypropylene resin, or an ethylene-propylene resin can be used, but the present invention is not limited thereto.

According to an embodiment of the present invention, the polyolefin resin may be included in an amount of about 30 to about 70 wt%, preferably about 40 to about 60 wt%, based on the redox flow battery membrane. In addition to the above-mentioned contents, additives such as inorganic particles and antioxidants may be contained in the balance. When the content of the polyolefin resin is within the above range, physical properties such as mechanical strength, heat resistance, and chemical resistance required for the redox flow cell separator can be sufficiently provided.

According to another embodiment of the present invention, the polyolefin resin may have a weight average molecular weight of about 300,000 to about 1,500,000 g / mol, and preferably about 300,000 to about 1,000,000 g / mol of high-density polyethylene ( HDPE). In the case of the polyolefin resin having a weight average molecular weight in the above range, the resistance to chemical species that can be used in redox flow cells such as Br ^- and Br ₂ is strong, and thus it can be usefully used in redox flow cell separators.

On the other hand, the polyolefin microporous membrane includes inorganic particles. The inorganic particles may be mixed with the polyolefin resin to form fine pores. When the polyolefin resin is an ethylene-propylene resin, the inorganic particles may function as a nucleating agent and improve the compatibility of ethylene and propylene.

According to an embodiment of the present invention, the inorganic particles may be contained in an amount of about 30 to about 70 wt%, and preferably about 40 to about 60 wt%, based on the redox flow battery membrane. When the inorganic particles are contained in an amount of less than about 30% by weight, the heat resistance of the redox flow cell separator to be produced may be deteriorated, and sufficient pores can not be secured. As a result, The resistance becomes large, and the performance of the battery may deteriorate. In addition, when the inorganic particles are contained in an amount of more than about 70% by weight, durability and chemical resistance are lowered, and the lifetime of the redox flow cell separator produced from the redox flow cell separator may be shortened.

According to another embodiment of the present invention, the inorganic particles may be, for example, silica particles, alumina particles, zirconia particles, or titania particles. Among them, silica may be preferably used. But is not limited thereto.

Further, the inorganic particles may have a number average particle diameter of about 10 to about 300 nm, preferably about 10 to about 150 nm, and more preferably about 40 to about 120 nm. When the number average particle diameter of the inorganic particles is less than about 10 nm, the pore diameter of the prepared microporous membrane becomes small, so that the permeation of ions through the membrane becomes difficult to increase the internal resistance of the battery, If it exceeds about 300 nm, the pore diameter of the microporous membrane becomes too large, and the selective permeability disappears. As a result, the performance of the battery may deteriorate due to the self-discharge phenomenon described above.

Further, according to another embodiment of the present invention, it is preferable that the BET surface area of the inorganic particles is about 100 to about 450 m ² / g. When the BET surface area is less than about 100 m < ² > / g, the quality of a film produced by aggregation of inorganic particles or the like in a process for producing a polyolefin microporous membrane for forming a sheet by melt kneading and extruding a polyolefin resin, Problems may arise. In addition, when the BET surface area exceeds about 450 m ² / g, the density of the silica particles in the kneading process is too low, the possibility of error in weighing is increased, the cost of the silica particles is high, have.

The redox flow cell separator according to an embodiment of the present invention may have a permeability of bromine (Br ₂ ) of 1.3 to 2.2 (* 10 ^-5 cm ² / min). When the redox flow cell separation membrane of the present invention is used in a chemical flow cell comprising bromine (Br ₂ ) or bromine ion (Br ^- ), when the permeability of bromine (Br ₂ ) , It is possible to increase the electric conductivity and to prevent the problem of deterioration of the performance of the battery due to the self-discharge phenomenon.

The redox flow cell membrane may have a water content of about 50 to about 150%, and preferably about 70 to 140%, expressed by the following formula (1).

[Formula 1]

In Equation (1)

W _dry is the dry weight of the redox flow battery separators, specifically, is a weight measured after drying for 24 hours The redox flow battery separators at 60 ℃ oven, W _wet can remove ions to the redox flow battery separators For 24 hours. ≪ tb >< TABLE > If the water content is less than about 50%, the separating film may have too low hydrophilicity to increase the resistance of the battery, resulting in a decrease in efficiency. When the water content exceeds about 150%, the selective permeability decreases, The efficiency of the battery may be lowered.

Meanwhile, the redox flow cell separator of the present invention can be produced by the following method. For example, the redox flow cell separator may include a step of melt-kneading a polyolefin resin, inorganic particles, and a plasticizer, transferring the melt, forming the sheet into a sheet, cooling and solidifying the sheet, Extraction, and the like, but the present invention is not limited thereto.

As the plasticizer, a nonvolatile solvent capable of forming a homogeneous solution at a temperature equal to or higher than the melting point of the polyolefin resin when mixed with the polyolefin resin can be used. For example, a hydrocarbon plasticizer including liquid paraffin and paraffin wax, Octyl and dibutyl phthalate; alcohol plasticizers including oleyl alcohol and stearyl alcohol; and the like. Particularly when the polyolefin resin is polyethylene, it is preferable to use liquid paraffin having no polar functional group in view of compatibility with polyethylene, but the present invention is not limited thereto. The polyolefin resin, inorganic particles, etc. usable in addition to the above plasticizer are as described above in the redox flow cell separator.

The ratio of the polyolefin resin, the inorganic particles and the plasticizer to be used is not particularly limited and may be appropriately selected within a range that uniform melting and kneading can be performed, molding can be performed in the form of a film, Particles, and plasticizer, it may be preferable to include about 30 to about 80 parts by weight of plasticizer, and about 40 to about 70 parts by weight of plasticizer, based on 100 parts by weight of the composition. When the content of the plasticizer is in the above range, moldability during melt-molding is excellent and stretchability is excellent, which may be preferable for thin film formation.

A method for melt kneading a polyolefin resin, an inorganic particle, and a plasticizer is a method in which a polyolefin resin and inorganic particles are put into a resin kneading apparatus such as an extruder or a kneader, and a plasticizer is further added thereto while heating and melting the resin, And a plasticizer is preferably kneaded to obtain a homogeneous solution. At this time, by dispersing the polyolefin resin, the inorganic particles, and the plasticizer in a pre-kneading step using a Henschel mixer or the like, the dispersibility of the inorganic particles can be increased.

The melt prepared above is transferred, formed into a sheet shape, and then cooled and solidified to prepare a microporous film precursor. It is preferable that the temperature at the time of molding the sheet after the transfer of the melt proceeds at a higher temperature than in the melt-kneading step. When the temperature at the time of melt-molding is lower than the temperature at the time of melt-kneading, the inorganic particles which have been finely dispersed in the melt-kneading step may be re-aggregated and the thickness of the film to be produced later may not be constant, and mechanical properties such as durability and heat resistance Can be lowered.

As the thermal conductor used for cooling and solidifying the microporous membrane precursor, metal, water, air, plasticizer, or the like can be used. In particular, a method of cooling by contacting with a metal roll is preferable because heat conduction efficiency is highest.

The method of extracting the plasticizer from the cooled and solidified microporous membrane precursor may be either a batch method or a continuous method. However, the method of immersing the microporous membrane in the extraction solvent to extract the plasticizer, . At this time, in order to suppress the contraction of the microporous membrane, it is preferable to confine the end of the microporous membrane during a series of processes of immersion and drying. Further, it is preferable that the residual amount of the plasticizer in the microporous film after the extraction is less than 1% by weight. The extraction solvent is preferably lower than the melting point of the polyolefin resin. Examples thereof include hydrocarbon solvents including n-hexane and cyclohexane, halogenated hydrocarbon solvents such as methylene chloride and 1,1,1-trichloroethane, hydrofluoroethers and hydrofluorocarbons, and the like. An alcohol solvent including ethanol and isopropanol, an ether including diethyl ether and tetrahydrofuran, a ketone solvent containing acetone and methyl ethyl ketone, and the like may be appropriately selected and used .

According to another aspect of the present invention, there is provided a redox flow cell including the redox flow cell separator.

According to an embodiment of the present invention, the redox flow cell comprises a redox flow battery separator; A pair of flow frames coupled to opposite sides of the separation membrane so as to face each other; A pair of electrodes coupled to an outer surface of the flow frame and facing the separation membrane; And an outer plate.

1 schematically illustrates a redox flow cell according to an embodiment of the present invention. Referring to FIG. 1, this redox-flow battery includes, for example, a redox flow cell separator 140; A pair of flow frames (130) coupled to opposite sides of the separation membrane so as to face each other; A pair of electrodes (120) coupled to an outer surface of the flow frame and facing the separation membrane; And the outer shape plate 110, but the present invention is not limited thereto.

The role and characteristics of the redox flow cell separator 140 included in the battery are as described above.

The flow frame 130 may serve as a passage through which the electrochemical reaction of the actual cell occurs, as well as the passage of the electrolyte. Specifically, the flow frame 130 serves as a passage for the electrolyte between the electrode 120 and the separator 140, and may be made of polyethylene, polypropylene, polyvinyl chloride, or the like. Such a flow frame 130 may have a thickness of 0.1 mm to 10.0 mm, or 0.3 mm to 1.5 mm, which may be desirable for efficient electrolyte migration and electrochemical reactions.

The electrode 120 serves to receive electrons generated in the electrochemical reaction of the active material and the electrolyte when the redox flow cell is driven. The electrode 120 may be formed of a graphite electrode, a graphite composite electrode, a carbon-plastic composite electrode, or the like. However, the present invention is not limited thereto.

The redox flow cell separator 140, the flow frame 130, and the electrode 120 may form a unit cell, and the redox flow cell may include at least one unit cell, The outer plate 110 for holding the outer shape of the battery can be included.

In addition, the redox flow cell may further include a tank in which different active materials in different oxidation states are stored, and a circulation pump that circulates the active material during charging / discharging into the unit cells, in addition to the unit cells.

For example, the outer plate 110, the electrode 120, the flow frame 130, and the outer frame 120 may be manufactured by a conventional method, for example, The redox flow cell separator 140, the flow frame 130, the electrode 120 and the outer plate 110 may be stacked in this order. The charge / discharge device 200 may be connected to the electrode 120, .

The redox flow cell including the redox flow cell separator may be a zinc-halogen redox flow cell, and may be a zinc-bromodeoxane flow cell because of physical and chemical characteristics of the separation membrane , But the present invention is not limited thereto.

According to an embodiment of the present invention, the redox flow cell including the redox flow cell separator may have an electrical resistance of about 2 to about 6 Ω · cm as measured at 25 ° C., It is possible to provide a redox-flow battery having improved battery performance.

Best Mode for Carrying Out the Invention Hereinafter, the function and effect of the present invention will be described in more detail through specific examples of the present invention. It is to be understood, however, that these embodiments are merely illustrative of the invention and are not intended to limit the scope of the invention.

< Example >

Redox  Preparation of flow cell membrane

[Example 1]

20% by weight of high-density polyethylene having a weight average molecular weight (Mw) of 400,000 g / mol (manufactured by Lotte Chemical Co., Ltd.);

20% by weight of silica particles having a number average particle diameter of 50 nm (trade name: Ebonic);

59.7% by weight of liquid paraffin (manufacturer: Mitsuno Kogyo Co., Ltd.) as a plasticizer;

0.3% by weight of pentaerythrityl-tetrakis- [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate] (manufactured by Chemtura) as an antioxidant;

Were mixed in a super mixer. The resulting mixture was fed to a twin-screw extruder extruder feed furnace. During melt-kneading in an extruder, the temperature was 210 DEG C and the screw rotation number was 160 rpm. For the prepared molten mixture, 230 Lt; RTI ID = 0.0 &gt; 80 C &lt; / RTI &gt; Lt; 0 &gt; C to obtain a sheet having a thickness of 600 mu m. The thickness of the film was measured using a Digital Micrometer (Mitutoyo).

This sheet was fixed to a fixed mold, impregnated with methylene chloride at room temperature for 10 minutes, and then the plasticizer was extracted to obtain a redox flow cell membrane.

[Example 2]

A redox flow cell membrane was obtained in the same manner as in Example 1, except that 15 wt% of silica particles were used instead of 20 wt% of silica particles.

[Example 3]

A redox flow cell membrane was obtained in the same manner as in Example 1, except that 20% by weight of silica particles were used instead of 25% by weight of silica particles.

[Example 4]

Except that high density polyethylene having a weight average molecular weight of 800,000 g / mol was used instead of high density polyethylene having a weight average molecular weight (Mw) of 400,000 g / mol, to obtain a redox flow battery separator.

[Example 5]

A redox flow cell membrane was obtained in the same manner as in Example 1 except that high density polyethylene having a weight average molecular weight of 1,200,000 g / mol was used instead of high density polyethylene having a weight average molecular weight (Mw) of 400,000 g / mol.

[Example 6]

A redox flow cell membrane was obtained in the same manner as in Example 1 except that silica particles having a number average particle diameter of 80 nm were used instead of the silica particles having a number average particle diameter of 50 nm.

[Example 7]

A redox flow cell membrane was obtained in the same manner as in Example 1, except that silica particles having a number average particle diameter of 120 nm were used instead of the silica particles having a number average particle diameter of 50 nm.

[Example 8]

A redox flow cell membrane was obtained in the same manner as in Example 1 except that a sheet having a thickness of 400 탆 was obtained by controlling extrusion conditions.

[Example 9]

A redox flow cell membrane was obtained in the same manner as in Example 1, except that a sheet having a thickness of 200 탆 was obtained by adjusting extrusion conditions.

[Comparative Example 1]

A redox flow cell membrane was obtained in the same manner as in Example 1, except that a sheet having a thickness of 800 탆 was obtained by controlling extrusion conditions.

[Comparative Example 2]

A redox flow cell membrane was obtained in the same manner as in Example 1, except that silica particles having a number average particle diameter of 1 占 퐉 were used instead of the silica particles having a number average particle diameter of 50 nm.

The manufacturing conditions of the redox flow cell membrane prepared in the above Examples and Comparative Examples are summarized in Table 1 below.

Polyethylene
Weight average molecular weight
(* 10 ⁵ g / mol) Silica particles
content
(weight%) Silica particles
Number average particle diameter
(nm) Film thickness
(탆) Example 1 4 49.6 50 600 Example 2 4 42.5 50 600 Example 3 4 54.9 50 600 Example 4 8 49.6 50 600 Example 5 12 49.6 50 600 Example 6 4 49.6 80 600 Example 7 4 49.6 120 600 Example 8 4 49.6 50 400 Example 9 4 49.6 50 200 Comparative Example 1 4 49.6 50 800 Comparative Example 2 4 49.6 1000 600

Redox  Flow cell manufacturing

As shown in FIG. 1, the redox flow cell separator fabricated in the above-described embodiment and the comparative example is used to separate the outer plate 110, the electrode 120, the flow frame 130, the separation membrane 140, The electrode 120, and the outer plate 110 were laminated in this order to fabricate a redox flow cell for testing. The manufactured redox flow cell is a zinc-bromine chemical flow battery. The electrode 120 was connected to a charge / discharge device 200 (WBCS3000, manufactured by WonAtec) to conduct experiments.

< Experimental Example >

Water content measurement

The moisture content of the membrane was measured to confirm the hydrophilicity of the redox flow cell membrane prepared in the above Examples and Comparative Examples.

The membrane of the redox flow cell membrane of 5 × 5 m ² was dried for 24 hours in an oven at 60 ° C., and the weight of the membrane was measured. After the impregnation was carried out in the deionized water, the water content was calculated using Equation 1 Respectively. .

[Formula 1]

In Equation (1)

W _dry is the dry weight of the redox flow cell membrane,

W _wet is the weight measured after impregnating the redox flow cell membrane with deionized water for 24 hours.

Pore average diameter  Measure

The redox flow cell membranes prepared in the above Examples and Comparative Examples were measured for porosimeter (Micromeritics, Autopore IV 9500). In the measurement, the pressure range was 0.5 to 60,000 psi, and the measurement was performed after pretreatment at 150 ° C for two hours.

bromine( Br ₂ ) Measurement of permeability

The bromine permeability of the zinc-bromine chemically-flowable cell fabricated using the redox flow cell separator of Examples and Comparative Examples was measured.

The manufactured single cell comprises a flow frame 130 for forming a flow path for moving the electrolyte based on the separation membrane 140, an electrode 120 for moving electrons, and an outer membrane 110 for maintaining the shape of the single cell Consists of.

The electrolyte solution in the electrolyte container is supplied to the unit cell through a pump. The charging and discharging current is 700 mA and the charging capacity is 2.17 Ah.

The permeability of the sample the cathode electrolytic solution and then automatically using the regular measuring the concentration of bromine (Br _2), bromine according to the following equation 2, and the same method (Br ₂₎ was calculated according to the elapsed time.

[Formula 2]

The expression in the 2 P is permeability of bromine (Br _2), S is the effective area of membrane (cm ^2), L is the thickness (cm), V is the volume (ml) of the electrolyte of the separator, t is time (minute), c _o is the initial concentration (M) of bromine (Br ₂ ), and c _t is the concentration (M) of bromine (Br ₂ ) at the measurement time.

Electrical resistance measurement

The electrical resistance of the zinc-bromine chemically-flowable cell fabricated using the redox flow cell separator of the Examples and Comparative Examples was measured.

The resistance was measured at 25 캜 using BT3563 manufactured by HIOKI.

During the measurement, the flow rate of the pump was 100 ml / min, and the membrane area was 35 cm ² .

The water content, pore average diameter, bromine permeability, and electrical resistance measurement results are summarized in Table 2 below.

Moisture content
(%) Average diameter of pores
(nm) Bromine permeability
(* 10 ^-5 cm ² / min) Electrical resistance
(Ω · cm) Example 1 90 38 1.7 4.1 Example 2 82 48 1.5 5.2 Example 3 113 25 1.9 3.2 Example 4 88 36 1.7 4.3 Example 5 89 37 1.6 4.2 Example 6 118 41 1.9 3.8 Example 7 133 56 2.1 3.5 Example 8 75 78 1.9 2.8 Example 9 66 110 1.9 2.3 Comparative Example 1 128 41 1.5 8.6 Comparative Example 2 150 130 2.4 4.2

Referring to Table 2, it can be seen that the examples are superior to the comparative examples in physical properties related to battery efficiency such as water content, bromine permeability, and electrical resistance.

That is, the thickness of the membrane 150 to 650㎛, embodiments of the present invention in which the average diameter of the pores 20 to 120nm range is shown a low bromine permeability Zinc ions (Zn ^{+ 2)} or bromide ion (Br ^-), etc. Small chemical species of a certain size or less can selectively permeate and exhibit selective permeability that effectively blocks migration of chemical species exceeding a certain size such as bromine (Br ₂ ), thereby preventing efficiency deterioration due to self-discharge Can be expected.

Further, in the case of the water content, the water content in the range of about 70 to 135% in the case of the present invention has adequate hydrophilicity and can prevent the permeation of bromine (Br ₂ ). On the other hand, In the case of Comparative Example 2, which is out of the range, it shows a large water content and a bromine permeability, and the selective permeability seems to be lowered, and it is expected that the efficiency of the battery will be lowered by self discharge.

The electrical resistance was measured to be about 2.3 to about 5.2 Ω · cm in the examples, and was found to have a generally good resistance value. However, in Comparative Example 1 in which the thickness of the separator was out of the range of the present invention, it was confirmed that although it had a relatively low bromine transmittance, the electric resistance was large. As a result, the internal resistance is increased and the performance of the battery may be deteriorated. As a result, it is not suitable as a redox flow battery separator.

110: outer plate
120: Electrode
130: flow frame
140: redox flow cell membrane
200: charge / discharge device

Claims (13)

A polyolefin microporous membrane comprising a polyolefin resin and an inorganic particle;
A thickness of 150 to 650 mu m and an average diameter of pores of 20 to 120 nm;
The polyolefin resin has a weight average molecular weight of 300,000 to 1,500,000 g / mol;
The inorganic particles have a number average particle diameter of 10 to 300 nm and a BET surface area of 100 to 450 m ² / g;
A redox flow cell separator having a water content of 50 to 150% defined by the following formula 1:
[Formula 1]

In Equation (1)
W _dry is the dry weight of the redox flow cell membrane,
W _wet is the weight measured after impregnating the redox flow cell membrane with deionized water for 24 hours.
The method according to claim 1,
And the polyolefin resin is contained in an amount of 30 to 70% by weight.
The method according to claim 1,
Wherein the polyolefin resin comprises at least one selected from the group consisting of polyethylene, polypropylene, and ethylene-propylene copolymer.
delete The method according to claim 1,
Wherein the inorganic particles are contained in an amount of 30 to 70% by weight.
The method according to claim 1,
Wherein the inorganic particles comprise at least one selected from the group consisting of silica, alumina, zirconia, and titania.
delete The method according to claim 1,
And the permeability of bromine (Br ₂ ) is 1.3 to 2.2 (* 10 ^-5 cm ² / min).
delete A redox flow cell comprising a redox flow cell separator according to any one of claims 1 to 3, 5, 6 and 8.
11. The method of claim 10,
Zinc-halogen redox flow cell.
11. The method of claim 10,
Redox flow cell separator; A pair of flow frames coupled to opposite sides of the separation membrane so as to face each other; A pair of electrodes coupled to an outer surface of the flow frame and facing the separation membrane; And an outer plate.
11. The method of claim 10,
A redox flow cell having an electrical resistance of 2 to 6 &lt; RTI ID = 0.0 &gt; OMEGA. &Lt; / RTI &

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