Electrochemical Properties of Imidazolium-Based Ionic Liquids for Non-Aqueous Vanadium Redox Flow Batteries

doi:10.22716/sckt.2025.13.4.009

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2025 Vol.13, Issue 4 Preview Page Next Page

Research Article

Electrochemical Properties of Imidazolium-Based Ionic Liquids for Non-Aqueous Vanadium Redox Flow Batteries 비수계 바나듐 레독스 흐름전지용 이미다졸륨계 이온성 액체의 전기화학적 특성 연구: Si-Bin Lee¹, Sun-Woo Park², and Seong-Ho Choi³
이시빈¹, 박선우², 최성호³; ¹Master’s Student, Department of Chemistry, Hannam University
²Undergraduate Student, Department of Chemistry, Hannam University
³Professor, Department of Chemistry, Hannam University

¹한남대학교 화학과 석사과정생
²한남대학교 화학과 학부생
³한남대학교 화학과 교수

31 December 2025. pp. 101-108

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Abstract

기존 수계 바나듐 레독스 흐름전지는 물의 전기분해로 약 1.5 V의 전압창 한계를 가져 고전압·고에너지밀도 ESS 설계에 제약이 있다. 본 연구는 이러한 한계를 극복하기 위해 V(acac)₃ 기반 비수계 레독스 흐름전지에서 사용할 이미다졸륨계 이온성 액체(DIBr, DIBF₄, DIPF₆)를 합성하고, 전기화학적 특성을 체계적으로 평가하였다. V(acac)₃와 지지 전해질 농도를 0.1 M로 고정하고 순환전압전류법(CV)을 수행하여 -2.5~1.0 V(Ag QRE 대비) 구간에서의 전기화학적 안정성, 피크 간 전위차 및 가역성을 조사한 결과, 가역성은 DIPF₆ > DIBF₄ > TBAPF₆ > DIBr 순으로 향상되었다. 이는 PF₆- 및 BF₄- 계열 전해질이 비수계 V(acac)₃ 시스템에서 넓은 안정창과 우수한 전하 전달 특성을 제공함을 의미하며, CV로부터 추정한 셀 전압은 약 2.2~2.5 V로 나타났다. 고에너지밀도 비수계 흐름전지 설계에 활용 가능함을 시사한다.

This study addresses the voltage limitation (~1.5 V) of conventional aqueous redox-flow batteries caused by water electrolysis, which restricts the development of high-voltage and high-energy-density ESS systems. To overcome this limitation, non-aqueous electrolytes and new supporting electrolytes are required. The purpose of this work is to synthesize imidazolium-based ionic liquids and evaluate their electrochemical behavior in a non-aqueous V(acac)₃ redox-flow battery. 1,3-dibutylimidazolium bromide (DIBr), 1,3-dibutylimidazolium tetrafluoroborate (DIBF₄), and 1,3-dibutylimidazolium hexafluorophosphate (DIPF₆) were synthesized and evaluated as supporting electrolytes in a non-aqueous vanadium(III) acetylacetonate (V(acac)₃) redox flow battery (RFB). Cyclic voltammetry (CV) indicated that two of the four ionic liquids were electrochemically stable in the V(acac)₃/acetonitrile electrolyte. The stability window was -2.5 to 1.0 V (vs Ag QRE). The concentrations of V(acac)₃ and the supporting electrolytes were both 0.1 M in all electrochemical tests. Under our test conditions, the apparent reversibility trended DIPF₆ > DIBF₄ > tetrabutylammonium hexafluorophosphate (TBAPF₆) > DIBr. These results suggest that the synthesized ionic liquids can serve as potential supporting electrolytes for non-aqueous RFBs. These properties enable higher operating voltages and broaden the usable temperature range, offering advantages for the design of high-energy-density non-aqueous RFB systems. From CV, the estimated cell potentials were approximately 2.2–2.5 V (DIPF₆ > DIBF₄ > TBAPF₆ ≈ DIBr).

Keywords

Redox flow battery

Vanadium triacetylacetonate

Ionic liquids

3-dibutylimidazolium bromide (DIBr)

3-dibutylimidazolium tetrafluoroborate (DIBF₄)

3-dibutylimidazolium hexafluorophosphate (DIPF₆)

tetrabutylammonium hexafluorophosphate (TBAPF₆)

References

A. Parasuraman, T. M. Lim, C. Menictas, and M. Skyllas-Kazacos, “Review of material research and development for vanadium redox flow battery applications”, Electrochimica Acta. 101: 27-40, 2013.
10.1016/j.electacta.2012.09.067
A. Z. Weber, M. M. Mench, J. P. Meyers, P. N. Ross, J. T. Gostick, and Q. Liu, “Redox flow batteries: a review”, Journal of Applied Electrochemistry. Vol. 41, No. 10, pp. 1137-1164, 2011.
10.1007/s10800-011-0348-2
C. Ponce de León, A. Frías-Ferrer, J. González-García, D. A. Szánto, and F. C. Walsh, “Redox flow cells for energy conversion”, Journal of Power Sources. Vol. 160, pp. 716-732, 2006.
10.1016/j.jpowsour.2006.02.095
X. Teng, J. Dai, J. Su, Y. Zhu, H. Liu, and Z. Song, “A high performance polytetrafluoroethene/Nafion composite membrane for vanadium redox flow battery application”, Journal of Power Sources, Vol. 240, pp. 131-139, 2013.
10.1016/j.jpowsour.2013.03.177
T. Herr, J. Noack, P. Fischer, and J. Tübke, “1,3-Dioxolane, tetrahydrofuran, acetylacetone and dimethyl sulfoxide as solvents for non-aqueous vanadium acetylacetonate redox flow-batteries”, Electrochimica Acta, Vol. 113, pp. 127-133, 2013.
10.1016/j.electacta.2013.09.055
D. Zhang, Q. Liu, X. Shi, and Y. Li, “Tetrabutylammonium hexafluorophosphate and 1-ethyl-3-methylimidazolium hexafluorophosphate ionic liquids as supporting electrolytes for non-aqueous vanadium redox flow batteries”, Journal of Power Sources, Vol. 203, pp. 201-205, 2012.
10.1016/j.jpowsour.2011.10.136
X. Teng, C. Sun, J. Dai, H. Liu, J. Su, and F. Li, “Solution casting Nafion/polytetrafluoroethylene membrane for vanadium redox flow battery application”, Electrochimica Acta, Vol. 88, pp. 725-734, 2013.
10.1016/j.electacta.2012.10.093
K. S. K. Chivukula, and Y. Zhao, “Next-generation vanadium redox flow batteries: harnessing ionic liquids for enhanced performance”, RSC Advances, Vol. 15, pp. 25310-25321, 2025.
10.1039/D5RA02901E
D. Zhang, H. Lan, and Y. Li, “The application of a non-aqueous bis(acetylacetone)ethylenediamine cobalt electrolyte in redox flow battery”, Journal of Power Sources, Vol. 217, pp. 199-203, 2012.
10.1016/j.jpowsour.2012.06.038
Q. Liu, A. E. S. Sleightholme, A. A. Shinkle, Y. Li, and L. T. Thompson, “Non-aqueous vanadium acetylacetonate electrolyte for redox flow batteries”, Electrochemistry Communications, Vol. 11, No. 12, pp. 2312-2315, 2009.
10.1016/j.elecom.2009.10.006
B. Chakrabarti, J. Rubio-Garcia, E. Kalamaras, V. Yufit, F. Tariq, C. T. J. Low, A. Kucernak, and N. Brandon. “Evaluation of a non-aqueous vanadium redox flow battery using a deep eutectic solvent and graphene-modified carbon electrodes via electrophoretic deposition”, Batteries, Vol. 6, No. 3, pp. 38, 2020.
10.3390/batteries6030038
S.-H. Lee, S.-H. Choi, G. Sai-Anand, K.-P. Lee, and A.-I. Gopalan, “Preparation of new self-humidifying composite membrane by incorporating graphene and phosphotungstic acid into sulfonated poly(ether ether ketone) film”, International Journal of Hydrogen Energy, Vol. 39, pp. 17162-17177, 2014.
10.1016/j.ijhydene.2014.07.181
L. Bahadori, R. Boyd, A. Warrington, M. S. Shafeeyan, and P. Nockemann, “Evaluation of ionic liquids as electrolytes for vanadium redox flow batteries”, Journal of Molecular Liquids, Vol. 317, 114017, 2020.
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J.-H. Kim, S. Ryu, S. Maurya, J.-Y. Lee, K.-W. Sung, J.-S. Lee, and S.-H. Moon, “Fabrication of a composite anion exchange membrane with aligned ion channels for a high-performance non-aqueous vanadium redox flow battery”, RSC Advances, Vol. 10, pp. 5010-5025, 2020.
10.1039/C9RA08616A

Information

Publisher :The Society of Convergence Knowledge
Publisher(Ko) :융복합지식학회
Journal Title :The Society of Convergence Knowledge Transactions
Journal Title(Ko) :융복합지식학회논문지
Volume : 13
No :4
Pages :101-108
DOI :https://doi.org/10.22716/sckt.2025.13.4.009

[1] A. Parasuraman, T. M. Lim, C. Menictas, and M. Skyllas-Kazacos, “Review of material research and development for vanadium redox flow battery applications”, Electrochimica Acta. 101: 27-40, 2013.
10.1016/j.electacta.2012.09.067

[2] A. Z. Weber, M. M. Mench, J. P. Meyers, P. N. Ross, J. T. Gostick, and Q. Liu, “Redox flow batteries: a review”, Journal of Applied Electrochemistry. Vol. 41, No. 10, pp. 1137-1164, 2011.
10.1007/s10800-011-0348-2

[3] C. Ponce de León, A. Frías-Ferrer, J. González-García, D. A. Szánto, and F. C. Walsh, “Redox flow cells for energy conversion”, Journal of Power Sources. Vol. 160, pp. 716-732, 2006.
10.1016/j.jpowsour.2006.02.095

[4] X. Teng, J. Dai, J. Su, Y. Zhu, H. Liu, and Z. Song, “A high performance polytetrafluoroethene/Nafion composite membrane for vanadium redox flow battery application”, Journal of Power Sources, Vol. 240, pp. 131-139, 2013.
10.1016/j.jpowsour.2013.03.177

[5] T. Herr, J. Noack, P. Fischer, and J. Tübke, “1,3-Dioxolane, tetrahydrofuran, acetylacetone and dimethyl sulfoxide as solvents for non-aqueous vanadium acetylacetonate redox flow-batteries”, Electrochimica Acta, Vol. 113, pp. 127-133, 2013.
10.1016/j.electacta.2013.09.055

[6] D. Zhang, Q. Liu, X. Shi, and Y. Li, “Tetrabutylammonium hexafluorophosphate and 1-ethyl-3-methylimidazolium hexafluorophosphate ionic liquids as supporting electrolytes for non-aqueous vanadium redox flow batteries”, Journal of Power Sources, Vol. 203, pp. 201-205, 2012.
10.1016/j.jpowsour.2011.10.136

[7] X. Teng, C. Sun, J. Dai, H. Liu, J. Su, and F. Li, “Solution casting Nafion/polytetrafluoroethylene membrane for vanadium redox flow battery application”, Electrochimica Acta, Vol. 88, pp. 725-734, 2013.
10.1016/j.electacta.2012.10.093

[8] K. S. K. Chivukula, and Y. Zhao, “Next-generation vanadium redox flow batteries: harnessing ionic liquids for enhanced performance”, RSC Advances, Vol. 15, pp. 25310-25321, 2025.
10.1039/D5RA02901E

[9] D. Zhang, H. Lan, and Y. Li, “The application of a non-aqueous bis(acetylacetone)ethylenediamine cobalt electrolyte in redox flow battery”, Journal of Power Sources, Vol. 217, pp. 199-203, 2012.
10.1016/j.jpowsour.2012.06.038

[10] Q. Liu, A. E. S. Sleightholme, A. A. Shinkle, Y. Li, and L. T. Thompson, “Non-aqueous vanadium acetylacetonate electrolyte for redox flow batteries”, Electrochemistry Communications, Vol. 11, No. 12, pp. 2312-2315, 2009.
10.1016/j.elecom.2009.10.006

[11] B. Chakrabarti, J. Rubio-Garcia, E. Kalamaras, V. Yufit, F. Tariq, C. T. J. Low, A. Kucernak, and N. Brandon. “Evaluation of a non-aqueous vanadium redox flow battery using a deep eutectic solvent and graphene-modified carbon electrodes via electrophoretic deposition”, Batteries, Vol. 6, No. 3, pp. 38, 2020.
10.3390/batteries6030038

[12] S.-H. Lee, S.-H. Choi, G. Sai-Anand, K.-P. Lee, and A.-I. Gopalan, “Preparation of new self-humidifying composite membrane by incorporating graphene and phosphotungstic acid into sulfonated poly(ether ether ketone) film”, International Journal of Hydrogen Energy, Vol. 39, pp. 17162-17177, 2014.
10.1016/j.ijhydene.2014.07.181

[13] L. Bahadori, R. Boyd, A. Warrington, M. S. Shafeeyan, and P. Nockemann, “Evaluation of ionic liquids as electrolytes for vanadium redox flow batteries”, Journal of Molecular Liquids, Vol. 317, 114017, 2020.
10.1016/j.molliq.2020.114017

[14] J.-H. Kim, S. Ryu, S. Maurya, J.-Y. Lee, K.-W. Sung, J.-S. Lee, and S.-H. Moon, “Fabrication of a composite anion exchange membrane with aligned ion channels for a high-performance non-aqueous vanadium redox flow battery”, RSC Advances, Vol. 10, pp. 5010-5025, 2020.
10.1039/C9RA08616A

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