KR101921299B1 - Anion exchange membrane for vanadium redox flow battery and vanadium redox flow battery comprising thereof - Google Patents

Abstract

(S) selected from the group consisting of an imidazole group, a benzimidazole group, a pyridine group, a triazole group, a tetrazole group or an amine group, Base polymer; And an anion exchanger doped with a sulfonic acid group; An anion exchange membrane for a vanadium redox flow cell. By including the base polymer, the crossover of vanadium ions is reduced to improve the coulombic efficiency of the vanadium redox flow battery, and the polymer containing the anion exchanger can be included to improve the voltage efficiency by lowering the resistance.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an anion exchange membrane for a vanadium redox flow battery and a vanadium redox flow battery comprising the same,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an anion exchange membrane for liquid crystalline vanadium redox flow cells and a vanadium redox flow cell comprising the same, and more particularly, to an anion exchange membrane comprising a basic polymer such as polybenzimidazole and having high conductivity, And a vanadium redox flow cell comprising the same.

In recent years, existing power generation systems, such as thermal power generation, facility stability and nuclear power generation, which cause greenhouse gas generation and environmental pollution problems due to the use of fossil fuels, suffer from 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.

In this regard, electric energy is converted into chemical energy, stored, and then converted into electrical energy if necessary, and development of a lightweight secondary battery is actively under way.

In particular, lithium-ion batteries, sodium-sulfur batteries, redox-flow batteries, ultra-high-capacity capacitors, and lead acid batteries are being developed or being developed as large-capacity power storage systems. Among them, high-capacity and high- Redox Flow Battery (RFB) is attracting attention.

Unlike other batteries, such a redox flow cell has a mechanism of storing energy by oxidation-reduction reaction of each ion in an anode and a cathode using an active material as an ion in an aqueous solution state not in a solid state, There are various types such as V / Br, Zn / Br and V / V depending on the couple. Among them, Vanadium Redox Flow Battery (VRB) has high open circuit voltage, Reductions can be used, and thus much research has been done in comparison with other types of redox flow cells.

On the other hand, the vanadium redox flow cell uses an electrolyte as a transfer medium and thus requires an ion exchange membrane. The ion exchange membrane is a core material that determines the lifetime and manufacturing cost of the battery of the vanadium redox flow battery, In order to be applied to a system using a strongly acidic substance including a metal as an electrolytic solution, it is required to have excellent acid resistance and oxidation resistance, low permeability, and excellent mechanical properties.

Particularly, in the ion exchange membrane, the V ⁴⁺ and V ⁵⁺ ions of the cathode electrolyte are crossovered to the cathode electrolyte, or the V ²⁺ and V ³⁺ ions of the cathode electrolyte are crossovered to the cathode electrolyte, So that the performance of the battery can be prevented from deteriorating.

However, current ion exchange membranes used in redox flow cells are generally used as separator membranes for lithium secondary batteries. Conventional separation membranes have a problem of causing crossover of ions between an anode and a cathode electrolyte and lowering energy density of a battery. Lt; / RTI >

For example, Nafion, a typical commercial ion exchange membrane, is widely used as an ion exchange membrane for redox flow cells due to its high ionic conductivity and excellent chemical stability. However, it is not only expensive but also has a drawback that vanadium ions easily permeate The transmission selectivity is low and the performance is degraded. Further, when the film thickness is increased to solve the above problem, there is a disadvantage that the voltage efficiency is lowered due to a large resistance.

K. J. Kim, M.-S. Park, Y.-J. Kim, J. H. Kim, S. X. Dou, M. Skyllas-Kazacos, A technology review of electrodes and reaction mechanisms in vanadium redox flow batteries, J. Mater. Chem. A, 2015, 3, 16913-16933.

In embodiments of the present invention, in one aspect, an imidazole group, a benzimidazole group, a pyridine group, a triazole group, a tetrazole group, A basic polymer comprising at least one member selected from the group consisting of (meth) acrylate; And an anion exchanger doped with a sulfonic acid group; To provide an anion exchange membrane for a vanadium redox flow battery.

Also in embodiments of the present invention, in another aspect, an anode; Cathode; The above-described anion exchange membrane disposed between the anode and the cathode; An anode electrolyte supply part including an electrolyte solution supplied to the anode; And a cathode electrolyte supply part including an electrolyte solution supplied to the cathode.

Exemplary embodiments of the present invention include compounds of the present invention which are comprised of an imidazole group, a benzimidazole group, a pyridine group, a triazole group, a tetrazole group or an amine group A base polymer comprising at least one member selected from the group consisting of: And an anion exchanger doped with a sulfonic acid group; An anion exchange membrane for a vanadium redox flow battery.

In exemplary embodiments of the present invention, an anode; Cathode; The above-described anion exchange membrane disposed between the anode and the cathode; An anode electrolyte supply part including an electrolyte solution supplied to the anode; And a cathode electrolyte supply part including an electrolyte solution supplied to the cathode.

According to exemplary embodiments of the present invention, a polymer such as polybenzimidazole including an anion exchange material is included in an anion exchange membrane to maintain a high coulombic efficiency by lowering the crossover of vanadium ions . In addition, when an anion exchange membrane containing the polymer is used, a large amount of water can be absorbed to increase the voltage efficiency by lowering the resistance, and ultimately, the vanadium redox flow A battery can be manufactured.

1 is a vanadium redox flow cell according to an embodiment of the present invention.
2 shows the coulombic efficiency of the membranes according to Comparative Examples 1 to 4 of the present invention.
3 shows the voltage efficiency of the films according to Comparative Examples 1 to 4 of the present invention.
4 shows the coulombic efficiency, voltage efficiency and energy efficiency of the membranes according to Examples 1 and 2 and Comparative Examples 5 to 7 of the present invention.
5 shows the energy efficiency of the membranes according to Examples 3 and 4 and Comparative Examples 7 and 8 of the present invention.

Term Definition

In this specification, when a component is referred to as "comprising ", it is to be understood that it may include other components as well, without departing from the other components unless specifically stated otherwise.

As used herein, the term " ion exchange membrane " means a membrane that separates a cathode electrolyte and an anode electrolyte in a vanadium redox flow cell and selectively moves ions generated during battery operation.

Illustrative Implementations  Explanation

Hereinafter, exemplary embodiments of the present invention will be described in detail.

In exemplary embodiments of the present invention, an imidazole group, a benzimidazole group, a pyridine group, a triazole group, a tetrazole group or an amine group A base polymer comprising at least one selected from the group consisting of: And an anion exchanger doped with a sulfonic acid group; An anion exchange membrane for a vanadium redox flow battery.

The performance of VRFB is mainly measured by coulombic efficiency (CE = 100% x discharge charge / charge charge), voltage efficiency (VE = 100% x average discharge voltage / average charge voltage) (energy efficiency, EE = CExVE). This efficiency must be further improved, and the ion exchange membrane is one of the most important factors affecting the efficiency.

Since the base polymer has high chemical stability in a strongly acidic solution containing a transition metal, the anion exchange membrane has excellent acid resistance and oxidation resistance. Particularly, when the base polymer is doped with a strong acid, it has two positive charges per repetitive unit and increases the oxidation stability of the material. Therefore, the acid resistance of the anion exchange membrane in the electrolyte of the vanadium redox flow cell is further increased.

In the case of the cation exchange membrane comprising the base polymer, since it is a cation exchange membrane, the permeability of the vanadium ion is high, so that the Coulomb efficiency is reduced due to continuous crossover of the vanadium ion. When the film thickness is increased to solve the above problem, the resistance increases to lower the voltage efficiency.

Thus, in the case of the present invention, by blending the base polymer with a polymer comprising an anion exchanger which is not a cation, the polymer comprising the anion exchanger blocks the transmission of the vanadium cation compared to the base polymer, so that the Coulomb efficiency of the anion- . It is also believed that the blending may have the effect of improving morphology, which improves the voltage efficiency.

In other words, the Coulomb efficiency is improved by reducing the crossover of vanadium ions by the addition of an anion exchange material, and by blending the polymer including the anion exchanger, the conductivity becomes high and the voltage efficiency becomes high, so that the total energy efficiency becomes high.

The charged groups may be DABCO or quaternary ammonium groups derived from trimethylamine, imidazolium or benzimidazolium groups, metallocene derivatives, guanidinium, and the like. Substituents are typically connected to the polymer through (CH ₂ ) x where x is 1 to 20.

In an exemplary embodiment, the base polymer is at least one selected from the group consisting of polybenzimidazole (PBI), polybenzimidazole-OO (PBI-OO), and O-polybenzimidazole It can be more than one.

The above polybenzimidazole (PBI), polybenzimidazole-OO (PBI-OO) and O-polybenzimidazole (O-PBI) are polymers of ladder type structure and contain a heterocycle in the main chain , Excellent in thermal stability, and excellent in elastic modulus due to interactions within the molecule. Therefore, the expansion of the anion exchange membrane can be reduced.

In an exemplary embodiment, the base polymer may be meta-polybenzimidazole (meta-PBI).

In an exemplary embodiment, the base polymer may be at least 50 wt%, and may be at most 99 wt%, based on the total weight of the anion exchange membrane for the vanadium redox flow battery cell.

When the content of the base polymer is less than 50% by weight, the stability of the anion exchange membrane and the coulombic efficiency can be reduced.

In an exemplary embodiment, the content of the polymer comprising an anion exchanger may be 1 to 50 wt% based on the total weight of the anion exchange membrane for the vanadium redox flow battery cell.

On the other hand, if the sulfone group is doped to the polymer including the anion exchanger and the sulfone group is immobilized by interaction with the multiple charges of vanadium ions, the channel size may be reduced at this point. Thus, the positive charge of the fixed vanadium ions can limit the access or transport of other vanadium ions, thereby reducing the crossover of the vanadium ions.

The backbone of the polymer comprising an anion-exchange group may be aliphatic or aromatic or a mixture thereof, and may include groups attached to the backbone or side chain or both. The charged groups may be DABCO or quaternary ammonium groups derived from trimethylamine, imidazolium or benzimidazolium groups, metallocene derivatives, guanidinium, and the like.

In an exemplary embodiment, the polymer comprising the anion exchanger is selected from the group consisting of -OH, -COOH, alkylated imidazolium, alkylated tetrazolium, alkylated triazolium, and alkylated Alkylated amonium. The substituents are typically connected to the polymer through (CH ₂ ) _x where x is 1 to 20.

In an exemplary embodiment, the polymer comprising the anion exchanger may comprise an ammonium group. Particularly, when an ammonium group is contained, anion exchange is easy and the conductivity is increased, so that the total energy efficiency can be improved.

In exemplary embodiments of the present invention, an anode; Cathode; The above-described anion exchange membrane disposed between the anode and the cathode; An anode electrolyte supply part including an electrolyte solution supplied to the anode; And a cathode electrolyte supply part including an electrolyte solution supplied to the cathode.

The anode and the cathode provide an active site for oxidation / reduction of the electrolytic solution. The anode and the cathode may be made of a common electrode material. For example, carbon nonwoven fabric, carbon fiber, carbon paper and the like are not particularly limited. .

The anode electrolyte supply part and the cathode electrolyte supply part may be composed of a tank for storing each electrolyte solution and a pump for transferring each electrolyte solution stored in the tank to the anode or the cathode.

The operation principle of the vanadium redox flow cell is briefly described as follows. The cathode electrolyte solution is stored in the tank on the cathode electrolyte supply portion, and the cathode electrolyte solution is delivered to the cathode through the pump active material inlet port during charge / And after the oxidation / reduction reaction is completed, it is transported again through the cathode active material outlet to the tank for the cathode electrolyte supply portion. The anode electrolyte solution also flows between the tank and the electrode as described above.

In an exemplary embodiment, the cathode electrolyte may be (VO ₂ ) ₂ SO ₄ , VO (SO ₄ ), or a mixture thereof. The cathode electrolyte solution may include a mixed solvent of strong acid or strong acid and water and a cathode electrolyte dissolved therein.

In an exemplary embodiment, the anode electrolyte may be VSO ₄ , V ₂ (SO ₄ ) _3, or a mixture thereof. The anode electrolyte solution may include a mixed solvent composed of strong acid or strong acid and water and an anode electrolyte dissolved therein.

The strong acid may specifically include sulfuric acid, hydrochloric acid, phosphoric acid, nitric acid and the like.

The cathode electrolyte and the anode electrolyte may further include a supporting electrolyte, and the supporting electrolyte may facilitate oxidation / reduction reaction of the redox pair, It forms the ion pair with the redox pair. The supporting electrolyte is not particularly limited in the present invention, and any known electrolyte may be used.

Specifically, the supporting electrolyte may be selected from the group consisting of LiBF ₄ , LiPF ₆ , LiClO ₄ , LiCH ₃ SO ₃ , Li (CF ₃ SO ₂ ) ₂ N, tetraethylammonium tetrafluoroborate (TEABF ₄ ), tetrabutylammonium tetra At least one selected from the group consisting of tetrabutyl ammonium tetrafluoroborate (TBABF ₄ ), NaBF ₄ , NaPF ₆ , trimethylsulfonylchloride, (NH ₄ ) ₂ SO _4, and combinations thereof .

Hereinafter, specific embodiments according to exemplary embodiments of the present invention will be described in more detail. It should be understood, however, that the invention is not limited to the embodiments described below, but that various embodiments of the invention may be practiced within the scope of the appended claims, It will be understood that the invention is intended to facilitate the practice of the invention to those skilled in the art.

Manufacturing example

Manufacturing example  One - Jonen's  synthesis

1.0015 g (4.24 mmol) of BIm (vacuum dried before being used at 60 캜 for 24 hours) were dissolved in 15 ml of anhydrous dimethylacetamide (DMAc) for 4 hours under argon atmosphere in T _room . Then 0.1786 g of NaH (60% in hexane) was added and stirred for 1 hour. Then, 1.1188 g of?,? '- dibromo-p-xylene (4.24 mmol) was added and the reaction temperature was increased to 80 ° C. After 48 hours the solution was precipitated in acetone and the precipitate was washed and vacuum filtered and vacuum dried at 60 DEG C for 24 hours or more.

_{^{1 H NMR (DMSO-d 6}} , δ (ppm)): 8.14 (m, 2H, benzimidazole), 7.77 (m, 2H, benzimidazole), 7.07 (s, phenyl), 5.50 (m, 4H, Methylene), 2.35 (s, 3H, methyl group at para position), 1.63 (s, 6H, methyl group at ortho position).

Example

Example  One

An anion exchange membrane containing polybenzimidazole -OO (PBI-OO) and ionene having the following structure in a ratio of 1: 1 was prepared.

First, commercial PBI-OO was dissolved in DMSO in T _room for 48 hours. Next, ions were added and stirring was continued for 24 hours at room temperature. After stirring, the solution was centrifuged at 15,000 RPM for 30 minutes at 20 < 0 > C. The centrifuged solution was cast on a glass plate with a speed of 3 mm s < ^-1 > and an air gap of 300 [mu] m, the casting being ca. 20 ° C and 21% relative humidity. The cast membrane was placed in an oven and dried at 40 +/- 1 DEG C for 72 hours under reduced pressure. After solvent evaporation, the membrane was placed in a room temperature water bath for 24 hours to remove the DMSO traces. The membrane was then dried in a vacuum oven at 60 DEG C for 48 hours. The film forming solution (about 18.2 wt%) and the thickness of the synthesized film are shown in Table 1 below.

Ionene: PBI-OO ratio Jonen (g) PBI-OO (g) DMSO (g) Dry thickness (탆) Example 1 1: 1 2.21 2.21 19.7 40.0 ± 4 Example 2 1: 0.7 2.61 1.81 19.7 41.0 ± 4

Example  2

Anion exchange membranes were prepared in the same manner as in Example 1 except that polybenzimidazole -OO (PBI-OO) and ionene were contained in a ratio of 0.7: 1 (see Table 1).

Example  3

An anion exchange membrane comprising meta-polybenzimidazole (meta-PBI) and FAA3, a polymer comprising an anion exchanger, was prepared to a thickness of 15 mu m.

Example  4

An anion exchange membrane comprising meta-polybenzimidazole (meta-PBI) and FAA3, a polymer comprising an anion exchanger, was prepared to a thickness of 25 mu m.

Comparative Example  One

A membrane containing commercially available meta-polybenzimidazole (meta-PBI) was prepared.

Comparative Example  2

Nafion 221 was prepared as a cation exchange membrane.

Comparative Example  3

An ion exchange membrane containing meta-polybenzimidazole (meta-PBI) and Nafion was prepared. (NP11)

First, 20 wt% of Nafion dispersion D2021 was filled in a glass vial and the solvent was first evaporated under ambient pressure at 60 DEG C and then under vacuum. The Nafion polymer residue was redissolved in 22.7 g DMAc and ammonia (8-30 wt% water) was added. Then, PBI powder (molecular weight = 56,000 g / mol) was added in a ratio of Nafion: meta-polybenzimidazole (meta-PBI) = 1: 1 to obtain a clear solution and dissolved with stirring. The solution was cast on a glass plate with a doctor blade (400-500 mu m gap width). The film was dried at 60 DEG C at ambient pressure for 1 hour and then dried under vacuum (see Table 2 below).

D2021 (g) Meta-PBI (g) Ammonia (ca. mg) Comparative Example 3 10 2 140 Comparative Example 4 5 3 50

Comparative Example  4

Except that PBI powder (molecular weight = 56,000 g / mol) was added at a ratio of Nafion: meta-polybenzimidazole (meta-PBI) = 1: 3 Respectively. (NP13)

Comparative Example  5

A film containing commercially available polybenzimidazole-OO (PBI-OO) was prepared.

Comparative Example  6

Nafion 211 was prepared as a cation exchange membrane.

Comparative Example  7

A 25 μm thick Nafion 212 was prepared as a cation exchange membrane.

Comparative Example  8

175 탆 thick Nafion 117 was prepared as a cation exchange membrane.

Experimental Example

The coulombic efficiency (CE) was determined by the ratio of the discharge time to the charge time. The minimum and maximum voltages were 1.0 and 1.7 V, respectively. The voltage efficiency (VE) was obtained as the ratio of the average discharge voltage to the average charge voltage. Energy efficiency (EE) was obtained by multiplying CE and VE.

Experimental Example  1- pure water meta - PBI membrane and meta - PBI / Nafion and Blended  Comparison of membranes

Referring to FIG. 2, the pure meta-PBI membrane according to Comparative Example 1 has a lower coulombic efficiency than that of Comparative Example 3 and Comparative Example 4 in which meta-PBI and Nafion are blended. However, referring to FIG. 3, it can be seen that the total voltage efficiency is higher than that of Comparative Examples 3 and 4 in which Comparative Example 1 is blended. This is thought to be due to the lower conductivity of Nafion.

Experimental Example  2- PBI -OO / Jonen  Membrane Nafion , pure PBI - OO film  compare

Referring to FIG. 4, it can be seen that the PBI-OO / Yonen membranes according to Examples 1 and 2 are superior in voltage efficiency to Nafion and pure PBI-OO films.

Experimental Example  3- PBI / FAA3  Membrane Nafion , pure PBI membrane  compare

Referring to FIG. 5, it can be seen that the pure Nafion of Comparative Examples 7 and 8 has a low coulombic efficiency while the anion exchange membranes according to Examples 3 and 4 are excellent in coulombic efficiency. The film efficiency was measured at 80 mA / cm < ² >.

210: cathode
220: anode
230: anion exchange membrane
280: cathode Electrolyte solution tank
281: cathode electrolyte solution pump
290: anode electrolyte solution tank
291: anode electrolyte solution pump

Claims (9)

(S) selected from the group consisting of an imidazole group, a benzimidazole group, a pyridine group, a triazole group, a tetrazole group or an amine group, Base polymer; And
A polymer comprising an anion exchanger; Lt; / RTI >
The polymer comprising the anion exchanger comprises a quaternary ammonium group,
An anion exchange membrane for a vanadium redox flow cell, wherein the polymer comprising the base polymer and the anion exchange group is blended.
The method according to claim 1,
Wherein the base polymer is at least one or more selected from the group consisting of polybenzimidazole (PBI), polybenzimidazole-OO (PBI-OO), and O-polybenzimidazole (O- Anodic exchange membranes for redox flow batteries.
The method according to claim 1,
Wherein the base polymer is meta-polybenzimidazole (meta-PBI).
The method according to claim 1,
Wherein the base polymer is at least 50 wt% based on the total weight of the anion exchange membrane for the vanadium redox flow battery.
delete delete Anode;
Cathode;
An anion exchange membrane according to any one of claims 1 to 4 disposed between the anode and the cathode;
An anode electrolyte supply part including an electrolyte solution supplied to the anode; And
And a cathode electrolyte supply portion including an electrolyte solution supplied to the cathode.
8. The method of claim 7,
Wherein the cathode electrolyte is (VO ₂ ) ₂ SO ₄ , VO (SO ₄ ), or a mixture thereof.
8. The method of claim 7,
Wherein the anode electrolyte is VSO ₄ , V ₂ (SO ₄ ) _3, or a mixture thereof.

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