KR102290292B1 - Electrolyte composition comprising ionic liquids substituted with ether group having improved ion conductivity for hybrid lithium-based redox flow battery - Google Patents

Abstract

According to the present invention, disclosed is an electrolyte composition for a hybrid lithium redox flow battery having increased ionic conductivity including an ether group-substituted ionic liquid. According to the present invention, the electrolyte composition increases ionic conductivity by including both TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl) and an ether group-substituted ionic liquid so as to realize a hybrid lithium redox flow battery having high energy density. According to the present invention, the hybrid lithium redox flow battery including the electrolyte composition has a higher discharging voltage and higher energy density than the existing things to be frequently used as a large-scale energy storage device with high output and high durability and to obtain long-term charge/discharge stability so as to have excellent battery life characteristics.

Description

Electrolyte composition comprising ionic liquids substituted with ether group having improved ion conductivity for hybrid lithium-based redox flow battery

The present invention relates to an electrolyte composition for a hybrid lithium redox flow battery having improved ionic conductivity comprising an ether group-substituted ionic liquid, and more particularly, TEMPO (2,2,6,6-tetramethylpiperidine Hybrid lithium redox flow with high energy density because ionic conductivity is improved by including -1-oxyl; 2,2,6,6-tetramethyl-piperidine-1-oxyl) and an ionic liquid substituted with a specific ether group It relates to an electrolyte composition for realizing a battery.

A redox flow battery is a secondary battery in which charging and discharging occur by oxidation and reduction reactions of electrolytes. The biggest difference from general batteries is that charging and discharging occur while circulating the electrolyte in which energy is stored. Until now, domestic and foreign related companies are striving to commercialize some of the redox flow battery aqueous systems, but there are problems with low energy density and low cell voltage, and crossover occurs due to the use of two types of metal salts as active materials. This has been pointed out as a drawback.

As a representative redox flow battery, it is an all-vanadium-based redox flow battery, and 2 out of vanadium ions such as ^{V(II), V(III), VO 2+} (IV), VO ^{2+ (V), which have different oxidation values.} Paper is used as a positive electrode active material and a negative electrode active material, respectively. Since all-vanadium-based redox flow batteries mainly dissolve vanadium salts in water in positive and negative electrolytes (aqueous system), if the battery is driven at a potential higher than 1.23V, which is the potential window of water, electrolytes caused by solvent decomposition It has a limit to the operating voltage and the battery life is also relatively short. In addition, it has been reported that it is difficult to drive at 0° C. or lower due to the thermodynamic properties of water, and that at a high temperature of 40° C. or higher, _{precipitation of vanadium ions, which is a positive active material, as V 2} O ₅ occurs (Patent Publication No. 10-2016-0035369).

In order to overcome such problems of the aqueous redox flow battery, a non-aqueous all-vanadium-based redox flow battery using an organic solvent has been developed, but there are still problems of low energy density and battery voltage, and two salts are used as active materials. As a result, crossover occurs, and it is not enough to apply all-vanadium-based redox flow batteries to medium and large-sized energy storage systems that require high capacity (high energy density). - Improvement measures such as using a ligand coordination compound as an active material are being developed (Patent Publication No. 10-2016-0035368), but an alternative is still required.

As a result of continuous research to supplement the problems of the conventional water-based/organic redox flow battery as described above, the present inventors predicted that the utility of the hybrid lithium redox flow battery (Li-RFB) would be very high, and high energy density when used The present invention has been completed by developing an electrolyte composition having improved ionic conductivity that can be realized.

Accordingly, it is an object of the present invention to provide an electrolyte composition having improved ionic conductivity comprising an ether group-substituted ionic liquid for a hybrid lithium redox flow battery implementing a high energy density.

Another object of the present invention is to provide a hybrid lithium redox flow battery implementing a high energy density comprising an electrolyte composition having improved ionic conductivity including the ether group-substituted ionic liquid.

In order to achieve the above object, the electrolyte composition for a hybrid lithium redox flow battery having improved ionic conductivity comprising an ether group-substituted ionic liquid according to the present invention is TEMPO (2,2,6,6-tetra Methylpiperidine-1-oxyl; 2,2,6,6-tetramethylpiperidine-1-oxyl), an ionic liquid substituted with a specific ether group, a supporting electrolyte, and an organic solvent.

As an example of the hybrid lithium redox flow battery in the present invention, as shown in FIG. 1 , the positive electrode active material is TEMPO dissolved in a liquid organic solvent, and the negative electrode active material is a solid redox active lithium metal (Li metal). characterized. As such, in a liquid/solid hybrid form, the electrolyte composition comprising the positive electrode active material may be configured to provide a flow from an external source operably connected to the cell. The reaction of each electrode is as follows:

In the charging process, electrons are generated as the reaction proceeds from the nitroxide (nitroxyl) radical to oxoammonium cation, and the generated electrons move to the opposite electrode through an external circuit to reduce lithium ions to lithium metal. . In the discharging process, the reaction proceeds in the opposite direction to that of charging.

The hybrid lithium redox flow battery uses lithium metal as an anode active material, thereby realizing a high voltage due to a high difference in standard reduction potential. It is possible to build a redox flow battery system with a large storage capacity having a density.

In the electrolyte composition of the present invention, TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl) as a positive electrode active material may be included in a concentration of 0.01 to 2.5 M, preferably 0.5 to 2.0 M It may be included in a concentration, and most preferably may be included in a concentration of 0.5 M.

A specific ether group-substituted ionic liquid that can be used together with the active material in the electrolyte composition of the present invention consists of the following cations and anions.

Cation: N,N,N-triethyl-4-methoxybutan-1-aminium [N,N,N-triethyl-4-methoxybutan-1-aminium; MeOC ₄ TEA]

Anion: bis(fluorosulfonyl)imide [bis(fluorosulfonyl)imide; FSI], bis(trifluoromethylsulfonyl)imide [bis(trifluoromethylsulfonyl)imide; TFSI], or hexafluorophosphate; PF ₆ ]

Preferably, the ether group-substituted ionic liquid used in the present invention is MeOC ₄ TEA-FSI [N,N,N-triethyl-4-methoxybutan-1-aminium bis(fluoro rosulfonyl) imide; N,N,N-triethyl-4-methoxybutan-1-aminium bis(fluorosulfonyl)imide], MeOC ₄ TEA-TFSI [N,N,N-triethyl-4-methoxybutan-1-aminium bis(tri fluoromethylsulfonyl)imide; N,N,N-triethyl-4-methoxybutan-1-aminium bis(trifluoromethylsulfonyl)imide], and MeOC ₄ TEA-PF ₆ [N,N,N-triethyl-4-methoxybutan-1-aminium hexa fluorophosphate; N,N,N-triethyl-4-methoxybutan-1-aminium hexafluorophosphate], most preferably MeOC ₄ TEA-FSI:

In the present invention, the ionic liquid substituted with an ether group is included in an amount of 1 to 15% by weight when the total electrolyte composition is 100% by weight.

It is preferable that the ether group-substituted ionic liquid used in the present invention consists only of cations and anions, and has a halide content of 20 ppm or less, a moisture content of 30 ppm or less, and no other impurities.

As the organic solvent in the electrolyte composition of the present invention, a carbonate-based solvent may be used. As the carbonate-based solvent, at least one selected from the group consisting of propylene carbonate (PC), ethylene carbonate (EC), and diethyl carbonate (DEC) may be used, and preferably a PC solvent Alternatively, an EC/DEC mixed solvent may be used. In the EC/DEC mixed solvent, a mixing ratio of EC:DEC is 7 to 1:3 to 1 (v/v), and preferably, EC:DEC is 7:3. Most preferably, a PC solvent is used.

When the organic active material is mixed with the electrolyte, the resistance is increased and the ionic conductivity is lowered, making it difficult to implement a hybrid lithium redox flow battery having a high capacity and high energy density.

As the supporting electrolyte in the present invention, LiPF ₆ , LiBF ₄ , LiAsF ₆ , LiClO ₄ , LiCF ₃ SO ₃ , LiCF ₃ SO ₃ , LiC(SO ₂ CF ₃ ) ₃ , LiN(CF ₃ SO ₂ ) ₂ and LiCH(CF) _{Among 3} SO ₂ ) ₂ , one or more lithium salts may be used, and most preferably LiPF ₆ . In the electrolyte composition of the present invention, the supporting electrolyte may be included in an amount of 0.1 to 1.0 M.

The electrolyte composition of the present invention may further include a known additive for improving stability, if necessary.

The electrolyte composition according to the present invention composed as described above has improved ionic conductivity by up to 7.94% by including the ionic liquid substituted with a specific ether group as described above together with TEMPO, which is a positive electrode active material (Table 4, FIGS. 4).

This is presumed to be due to the fact that the ionic liquid substituted with a specific ether group as described above improves the degree of dissociation of TEMPO, which is a positive active material, and improves the mobility of ions (transference number). In addition, due to the non-volatile characteristics of the ether group-substituted ionic liquid, the volatility of the active material, TEMPO, is suppressed, so that TEMPO can be stably present in the electrolyte, so that long-term charge/discharge stability can be ensured, so that it has excellent battery life characteristics. do.

In addition, the electrolyte composition according to the present invention has a low viscosity of 5.32 to 9.42 cP (0.00532 to 0.00942 Pa·s), thereby increasing the discharge capacity and reversible efficiency, thereby improving the battery efficiency of charging and discharging (Table 6).

According to another object of the present invention, the present invention provides a hybrid lithium redox flow battery comprising an electrolyte composition having improved ionic conductivity comprising the ether group-substituted ionic liquid.

The hybrid lithium redox flow battery may include a structure as described above and illustrated by way of example in FIG. 1 . The construction and assembly of the current collector, the porous separator, the electrolyte, and an external source may be conventionally performed in the art.

The hybrid lithium redox flow battery comprising the electrolyte composition having improved ionic conductivity including the ether group-substituted ionic liquid according to the present invention can have a high discharge voltage and high energy density, so it can be used as a large-scale energy storage device possible. In addition, the volatility problem caused by long-term charging/discharging in TEMPO, which is an organic active material, is remarkably supplemented, so that it can have the advantage of improving long-term battery life through long-term stability.

The electrolyte composition according to the present invention is suitable for use as an electrolyte for a hybrid lithium redox flow battery capable of realizing high energy density by enhancing ionic conductivity even when TEMPO is used as a positive electrode active material.

In addition, since the electrolyte composition according to the present invention has a low viscosity, it is possible to increase the discharge capacity and reversible efficiency, thereby improving the battery efficiency of charging and discharging.

The hybrid lithium redox flow battery comprising the electrolyte composition according to the present invention can have a higher discharge voltage and higher energy density than in the prior art, so it has high utility as a large-scale energy storage device with high output and high durability, and long-term charge/discharge Since stability can be secured, excellent battery life characteristics can be provided.

1 is a schematic diagram showing an example of the configuration of a hybrid lithium redox flow battery in which an electrolyte composition according to the present invention is used.
2 is a PC solvent, when the active material is TEMPO and the cation of the ionic liquid is [MeOC ₄ TEA], the ionic conductivity increase/decrease rate of the electrolyte composition (Examples 1 to 3) according to the anion change of the ether group-substituted ionic liquid And, when the active material is oxo-TEMPO and the cation of the ionic liquid is [MeOC ₄ TEA], the ionic conductivity increase/decrease rate of the electrolyte composition (Comparative Examples 1-3) according to the anion change of the ether group-substituted ionic liquid was compared It is a graph.
3 is an electrolytic solution composition according to the anion change of the ether group-substituted ionic liquid when the active material is TEMPO and the cation of the ionic liquid is [MeOC _{4 TEA] in the EC/DEC (7/3) mixed solvent (Example 1} ~3) of ion conductivity increase/decrease rate and electrolyte composition according to the change in anion of the ether group-substituted ionic liquid when the active material is oxo-TEMPO and the cation of the ionic liquid is [MeOC _{4 TEA] (Comparative Examples 1-3)} It is a graph comparing the increase/decrease rate of ionic conductivity of
Figure 4 is an electrolytic solution composition according to the anion change of the ether group-substituted ionic liquid when the active material is TEMPO and the cation of the ionic liquid is [MeOC _{4 TEA] in the EC/DEC (1/1) mixed solvent (Example 1} ~3) of ion conductivity increase/decrease rate and electrolyte composition according to the change in anion of the ether group-substituted ionic liquid when the active material is oxo-TEMPO and the cation of the ionic liquid is [MeOC _{4 TEA] (Comparative Examples 1-3)} It is a graph comparing the increase/decrease rate of ionic conductivity of
5 is a graph showing the ionic conductivity increase/decrease rate of the electrolyte composition according to the anion change of the ether group-substituted ionic liquid when the cation of the ionic liquid in the PC solvent is [MeOC ₄ MMor] or [MeOC _{4 MPyr].}
6 is an EC/DEC (7/3) mixed solvent, when the cation of the ionic liquid is [MeOC ₄ MMor] or [MeOC ₄ MPip], the ionic conductivity of the electrolyte composition according to the anion change of the ether group-substituted ionic liquid It is a graph showing the increase/decrease rate.
Figure 7 is the ionic conductivity of the electrolyte composition according to the anion change of the ether group-substituted ionic liquid when _{the cation of the ionic liquid is [MeOC 4} MPip] or [MeOC ₄ MIm] in the EC/DEC (1/1) mixed solvent It is a graph showing the increase/decrease rate.

Hereinafter, the present invention will be described in more detail by way of Examples. These preparations and examples are only for illustrating the present invention in more detail, and it will be apparent to those of ordinary skill in the art that the scope of the present invention is not limited to these examples.

Preparation Example 1: Preparation of an electrolyte composition comprising an ether group-substituted ionic liquid

<Material>

(1) The following two types were prepared as active materials:

TEMPO (Alfa aesar or TCI),

Oxo-TEMPO (4-Oxo-2,2,6,6-tetramethylpiperidine 1-oxyl; TCI)

(2) Solvent: PC (Panax Etec Co. Ltd),

EC : Mixed solvent of DEC (7 : 3 (v/v)) (Panax Etec Co. Ltd)

EC : DEC mixed solvent (1 : 1 (v/v)) (Panax Etec Co. Ltd)

(3) Supporting electrolyte: LiPF ₆ (Panax Etec Co. Ltd)

(4) The ionic liquid substituted with an ether group was synthesized by combining 4 types of cations and 3 types of anions as follows, and 11 types were prepared (Mediforum Pharmaceutical Co., Ltd.):

ionic liquid Chemical name (full name) constitutional formula MeOC ₄ TEA-FSI N,N,N-triethyl-4-methoxybutan-1-aminium bis(fluorosulfonyl)imide
N,N,N-triethyl-4-methoxybutan-1-aminium bis(fluorosulfonyl)imide

MeOC ₄ TEA-TFSI N,N,N-triethyl-4-methoxybutan-1-aminium bis(trifluoromethylsulfonyl)imide
N,N,N-triethyl-4-methoxybutan-1-aminium bis(trifluoromethylsulfonyl)imide

MeOC ₄ TEA-PF ₆ N,N,N-triethyl-4-methoxybutane-1-aminium hexafluorophosphate
N,N,N-triethyl-4-methoxybutan-1-aminium hexafluorophosphate

MeOC ₄ MMor-FSI 4-(4-Methoxybutyl)-4-methylmorpholine-4-ium bis(fluorosulfonyl)imide
4-(4-methoxybutyl)-4-methylmorpholin-4-ium bis(fluorosulfonyl)imide

MeOC ₄ MPyr-TFSI 1-(4-methoxybutyl)-1-methylpyrrolidin-1-ium bis(trifluoromethylsulfonyl)imide 1-(4-methoxybutyl)-1-methylpyrrolidin-1-ium bis(trifluoromethylsulfonyl) imide

MeOC ₄ MMor-PF ₆ 4-(4-methoxybutyl)-4-methylmorpholin-4-ium hexafluorophosphate 4-(4-methoxybutyl)-4-methylmorpholin-4-ium hexafluorophosphate

MeOC ₄ MPip-FSI 1-(4-methoxybutyl)-1-methylpiperidin-1-ium bis(fluorosulfonyl)imide 1-(4-methoxybutyl)-1-methylpiperidin-1-ium bis(fluorosulfonyl)imide

MeOC ₄ MPip-TFSI 1-(4-methoxybutyl)-1-methylpiperidin-1-ium bis(trifluoromethylsulfonyl)imide 1-(4-methoxybutyl)-1-methylpiperidin-1-ium bis(trifluoromethylsulfonyl) imide

MeOC ₄ MPip-PF ₆ 1-(2-methoxybutyl)-1-methylpiperidin-1-ium hexafluorophosphate 1-(2-methoxybutyl)-1-methylpiperidin-1-ium hexafluorophosphate

MeOC ₄ MIm-FSI 1-(4-Methoxybutyl)-3-methyl-1H-imidazol-3-ium Bis(fluorosulfonyl)imide 1-(4-methoxybutyl)-3-methyl-1H-imidazol-3-ium bis(fluorosulfonyl)imide

MeOC ₄ MIm-TFSI 1-(4-methoxybutyl)-3-methyl-1H-imidazol-3-ium bis(trifluoromethylsulfonyl)imide 1-(4-methoxybutyl)-3-methyl-1H-imidazol-3 -ium bis(trifluoromethylsulfonyl)imide

<Production method>

As shown in the composition of Table 2 below, in a solution obtained by mixing and dissolving _{1M LiPF 6 in each of the three solvents, three ionic liquids MeOC 4} TEA-FSI, MeOC ₄ TEA-TFSI and MeOC ₄ TEA-PF ₆ (cation [MeOC ₄ TEA] and the anions are different) were added at 5 wt %, respectively, and mixed by vortexing for 15 seconds, and then two active materials TEMPO and oxo-TEMPO were added at a concentration of 0.5 M, respectively, and 30 ~ The electrolyte composition was prepared by mixing by vortexing for 40 seconds.

menstruum Active material (0.5M) support
electrolyte Ionic liquid (5w%) Example 1 PC TEMPO 1.0M
LiPF ₆ IL-1 (MeOC ₄ TEA-FSI) Example 2 IL-2 (MeOC ₄ TEA-TFSI) Example 3 IL-3 (MeOC ₄ TEA-PF ₆ ) Comparative Example 1 PC Oxo-TEMPO 1.0M
LiPF ₆ IL-1 (MeOC ₄ TEA-FSI) Comparative Example 2 IL-2 (MeOC ₄ TEA-TFSI) Comparative Example 3 IL-3 (MeOC ₄ TEA-PF ₆ ) Example 4 EC/DEC
(7/3) TEMPO 1.0M
LiPF ₆ IL-1 (MeOC ₄ TEA-FSI) Example 5 IL-2 (MeOC ₄ TEA-TFSI) Example 6 IL-3 (MeOC ₄ TEA-PF ₆ ) Comparative Example 4 EC/DEC
(7/3) Oxo-TEMPO 1.0M
LiPF ₆ IL-1 (MeOC ₄ TEA-FSI) Comparative Example 5 IL-2 (MeOC ₄ TEA-TFSI) Comparative Example 6 IL-3 (MeOC ₄ TEA-PF ₆ ) Example 7 EC/DEC
(1/1) TEMPO 1.0M
LiPF ₆ IL-1 (MeOC ₄ TEA-FSI) Example 8 IL-2 (MeOC ₄ TEA-TFSI) Example 9 IL-3 (MeOC ₄ TEA-PF ₆ ) Comparative Example 7 EC/DEC
(1/1) Oxo-TEMPO 1.0M
LiPF ₆ IL-1 (MeOC ₄ TEA-FSI) Comparative Example 8 IL-2 (MeOC ₄ TEA-TFSI) Comparative Example 9 IL-3 (MeOC ₄ TEA-PF ₆ )

As shown in Table 3 below, 9 types of ionic liquids in combination with the above 3 types of anions and cations [MeOC ₄ MMor], [MeOC ₄ MPyr], [MeOC ₄ MPip], or [MeOC _{4 MIm] were used except that} And the electrolyte composition was prepared in the same manner as above.

menstruum Active material (0.5M) support
electrolyte Ionic liquid (5w%) Comparative Example 10 PC TEMPO 1.0M
LiPF ₆ MeOC ₄ MMor-FSI Comparative Example 11 MeOC ₄ MPyr-TFSI Comparative Example 12 MeOC ₄ MMor-PF ₆ Comparative Example 13 EC/DEC
(7/3) TEMPO 1.0M
LiPF ₆ MeOC ₄ MPip-FSI Comparative Example 14 MeOC ₄ MMor-PF ₆ Comparative Example 15 MeOC ₄ MPip-TFSI Comparative Example 16 EC/DEC
(1/1) TEMPO 1.0M
LiPF ₆ MeOC ₄ MPip-PF ₆ Comparative Example 17 MeOC ₄ MIm-FSI Comparative Example 18 MeOC ₄ MIm-TFSI

In addition, in order to analyze the increase or decrease in ionic conductivity, the reference electrolyte compositions of Examples 1 to 9 and Comparative Examples 1 to 18 were prepared in the same manner without adding an ionic liquid.

Test Example 1: Analysis of ionic conductivity and viscosity of electrolyte composition containing ether group-substituted ionic liquid

<Ion conductivity>

For the Examples, Comparative Examples and Reference electrolyte compositions prepared above, the resistance was measured at room temperature using an electrochemical impedance spectroscopy (EIS), Zahner ennium) (electrode used: PEEK + SUS material separately Prepared electrode holder, 2 probes; Frequency: 1MHz ~ 1Hz (10 mV); Analysis method: Nyquist plot), ion conductivity (Z) according to the following formula, and K value (L/A) using the following STD conductivity ) after the calculation, the measured resistance value was substituted for the calculation, and the ionic conductivity increase/decrease rate of the electrolyte composition of each Example and the electrolyte composition of Comparative Example was calculated compared to the ionic conductivity of the reference electrolyte composition, and the results are shown in Tables 4 and Tables 5 and Figs. 2 to 7, respectively:

STD Conductivity = 1/Resistance x (L/A)

Conductivity = 1/resistance x (L/A)

PC (1=v) 1M LiPF ₆ , K value: 5.8 mS/cm (5.8 x 10 ^-3 S/cm)

ionic conductivity Reference (without ionic liquid addition) Increase/decrease rate (%) Example 1 5.48 5.07 7.94 Example 2 5.27 5.07 3.87 Example 3 5.22 5.07 2.83 Example 4 7.30 6.91 5.72 Example 5 6.98 6.91 1.01 Example 6 7.20 6.91 4.21 Example 7 6.99 6.68 4.71 Example 8 6.78 6.68 1.60 Example 9 6.74 6.68 1.02 Comparative Example 1 4.24 4.54 -6.62 Comparative Example 2 4.45 4.54 -2.05 Comparative Example 3 4.52 4.54 -0.51 Comparative Example 4 5.88 6.34 -7.19 Comparative Example 5 6.12 6.34 -3.48 Comparative Example 6 6.14 6.34 -3.19 Comparative Example 7 5.65 6.22 -9.15 Comparative Example 8 5.80 6.22 -6.69 Comparative Example 9 5.94 6.22 -4.44

ionic conductivity Reference (without ionic liquid addition) Increase/decrease rate (%) Comparative Example 10 4.83 5.07 -4.78 Comparative Example 11 4.70 5.07 -7.29 Comparative Example 12 4.38 5.07 -13.70 Comparative Example 13 6.32 6.91 -8.54 Comparative Example 14 6.26 6.91 -9.39 Comparative Example 15 6.09 6.91 -11.80 Comparative Example 16 6.49 6.68 -2.84 Comparative Example 17 6.41 6.68 -.3.98 Comparative Example 18 6.11 6.68 -8.47

As shown in Table 4 and FIGS. 2 to 4, as an active material in an organic solvent, TEMPO and a cation are [MeOC ₄ TEA], and an anion is [TFSI], [FSI] or [PF ₆ ] ether group-substituted ionic It can be seen that the ionic conductivity of the electrolyte composition including the liquid was increased to 7.94%, while the ionic conductivity of the electrolyte composition to which oxo-TEMPO was added as an active material was rather decreased (up to -9.15%).

Therefore, it can be seen that the ionic conductivity is enhanced only when the TEMPO active material and the ester group-substituted ionic liquid are used together in an organic solvent. In particular, when the ionic liquid was MeOC ₄ TEA-FSI, the increase in ionic conductivity was the highest.

On the other hand, as shown in Table 5 and FIGS. 5 to 7, even when TEMPO is used as an active material in an organic solvent, the cations of the ionic liquid are [MeOC ₄ MMor], [MeOC ₄ MPyr], [MeOC ₄ MPip], Alternatively, in the case of [MeOC ₄ MIm], it can be confirmed that the ionic conductivity is reduced (up to -8.47%) even if the anion is [TFSI], [FSI] or [PF _{6 ].}

Therefore, it can be seen that the ionic conductivity of the ether group-substituted ionic liquid when used together with the TEMPO active material _{is improved only when the cation is [MeOC 4 TEA].}

<Viscosity>

For the electrolyte compositions of Examples 1 to 9, the viscosity was measured using a viscometer (Brookfield LVDV-11+Pro) (Spindle: SC4-18, Sample chamber: SC4-13R, Chamber Temp. 24.6°C). is shown in Table 6:

ionic liquid menstruum Viscosity
(cP) Viscosity
(Pa s) Example 1 IL-1 (MeOC ₄ TEA-FSI) PC 9.04 0.00904 Example 2 IL-2 (MeOC ₄ TEA-TFSI) 8.88 0.00888 Example 3 IL-3 (MeOC ₄ TEA-PF ₆ ) 9.42 0.00942 Example 4 IL-1 (MeOC ₄ TEA-FSI) EC/DEC
(7/3) 6.22 0.00622 Example 5 IL-2 (MeOC ₄ TEA-TFSI) 6.13 0.00613 Example 6 IL-3 (MeOC ₄ TEA-PF ₆ ) 6.49 0.00649 Example 7 IL-1 (MeOC ₄ TEA-FSI) EC/DEC
(1/1) 5.46 0.00546 Example 8 IL-2 (MeOC ₄ TEA-TFSI) 5.32 0.00532 Example 9 IL-3 (MeOC ₄ TEA-PF ₆ ) 5.62 0.00562

The viscosity of the electrolyte compositions of Examples 1 to 9 according to the present invention was confirmed to be 5.32 to 9.42 cP (0.00532 to 0.00942 Pa·s). Therefore, since the electrolyte composition according to the present invention has a low viscosity, it is possible to increase the discharge capacity and the reversible efficiency, thereby improving the battery efficiency of charging and discharging.

Claims (10)

An electrolyte composition for a hybrid lithium redox flow battery comprising 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) as an active material, an ether group-substituted ionic liquid, a supporting electrolyte, and an organic solvent,
The ether group-substituted ionic liquid has a cation of N,N,N-triethyl-4-methoxybutan-1-aminium [MeOC ₄ TEA], and an anion of bis(fluorosulfonyl)imide [FSI] ], bis (trifluoromethylsulfonyl) imide [TFSI] and hexafluorophosphate [PF ₆ ] The electrolyte composition for a hybrid lithium redox flow battery, characterized in that any one selected from the group consisting of.
The electrolyte composition for a hybrid lithium redox flow battery according to claim 1, wherein the TEMPO is contained in a concentration of 0.5 to 2.0M.
delete The method of claim 1, wherein the ionic liquid substituted with an ether group is N,N,N-triethyl-4-methoxybutan-1 _{-aminium bis(fluorosulfonyl)imide [MeOC 4} TEA-FSI] An electrolyte composition for a hybrid lithium redox flow battery, characterized in that
The electrolyte composition for a hybrid lithium redox flow battery according to claim 1, wherein the ionic liquid substituted with the ether group is included in an amount of 1 to 15 wt%.
The method of claim 1, wherein the supporting electrolyte is LiPF ₆ , LiBF ₄ , LiAsF ₆ , LiClO ₄ , LiCF ₃ SO ₃ , LiCF ₃ SO ₃ , LiC(SO ₂ CF ₃ ) ₃ , LiN(CF ₃ SO ₂ ) ₂ and LiCH (CF ₃ SO ₂ ) _{2 An} electrolyte composition for a hybrid lithium redox flow battery, characterized in that at least one selected from the group consisting of.
The electrolyte composition for a hybrid lithium redox flow battery according to claim 6, wherein the supporting electrolyte is LiPF ₆ and is contained in a concentration of 0.1 to 1.0M.
The electrolyte composition for a hybrid lithium redox flow battery according to claim 1, wherein the electrolyte composition has an improved ionic conductivity up to 7.94% and a low viscosity of 5.32 to 9.42 cP.
A hybrid lithium redox flow battery comprising the electrolyte composition according to any one of claims 1, 2 and 4 to 8.
[10] The hybrid lithium redox flow battery according to claim 9, wherein in the hybrid lithium redox flow battery, the positive active material is TEMPO dissolved in a liquid organic solvent, and the negative active material is a solid redox active lithium metal.

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