Pairing nitroxyl radical and phenazine with electron-withdrawing/-donating substituents in “water-in-ionic liquid” for high-voltage aqueous redox flow batteries
Aqueous redox-active organic materials-base electrolytes are sustainable alternatives to vanadium-based electrolyte for redox flow batteries (RFBs) due to the advantages of high ionic conductivity, environmentally benign, safety and low cost. However, the underexplored redox properties of organic ma...
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KeAi Communications Co., Ltd.
2024-04-01
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| Series: | Green Energy & Environment |
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| Online Access: | http://www.sciencedirect.com/science/article/pii/S2468025722001364 |
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| author | Zhifeng Huang Rolf Hempelmann Yiqiong Zhang Li Tao Ruiyong Chen |
| author_facet | Zhifeng Huang Rolf Hempelmann Yiqiong Zhang Li Tao Ruiyong Chen |
| author_sort | Zhifeng Huang |
| collection | DOAJ |
| description | Aqueous redox-active organic materials-base electrolytes are sustainable alternatives to vanadium-based electrolyte for redox flow batteries (RFBs) due to the advantages of high ionic conductivity, environmentally benign, safety and low cost. However, the underexplored redox properties of organic materials and the narrow thermodynamic electrolysis window of water (1.23 V) hinder their wide applications. Therefore, seeking suitable organic redox couples and aqueous electrolytes with a high output voltage is highly suggested for advancing the aqueous organic RFBs. In this work, the functionalized phenazine and nitroxyl radical with electron-donating and electron-withdrawing group exhibit redox potential of −0.88 V and 0.78 V vs. Ag, respectively, in “water-in-ionic liquid” supporting electrolytes. Raman spectra reveal that the activity of water is largely suppressed in “water-in-ionic liquid” due to the enhanced hydrogen bond interactions between ionic liquid and water, enabling an electrochemical stability window above 3 V. “Water-in-ionic liquid” supporting electrolytes help to shift redox potential of nitroxyl radical and enable the redox activity of functionalized phenazine. The assembled aqueous RFB allows a theoretical cell voltage of 1.66 V and shows a practical discharge voltage of 1.5 V in the “water-in-ionic liquid” electrolytes. Meanwhile, capacity retention of 99.91% per cycle is achieved over 500 charge/discharge cycles. A power density of 112 mW cm−2 is obtained at a current density of 30 mA cm−2. This work highlights the importance of rationally combining supporting electrolytes and organic molecules to achieve high-voltage aqueous RFBs. |
| first_indexed | 2024-03-07T19:41:19Z |
| format | Article |
| id | doaj.art-2a65e5a6f02b47d4b4b6c09fe2756427 |
| institution | Directory Open Access Journal |
| issn | 2468-0257 |
| language | English |
| last_indexed | 2024-03-07T19:41:19Z |
| publishDate | 2024-04-01 |
| publisher | KeAi Communications Co., Ltd. |
| record_format | Article |
| series | Green Energy & Environment |
| spelling | doaj.art-2a65e5a6f02b47d4b4b6c09fe27564272024-02-29T05:20:08ZengKeAi Communications Co., Ltd.Green Energy & Environment2468-02572024-04-0194713722Pairing nitroxyl radical and phenazine with electron-withdrawing/-donating substituents in “water-in-ionic liquid” for high-voltage aqueous redox flow batteriesZhifeng Huang0Rolf Hempelmann1Yiqiong Zhang2Li Tao3Ruiyong Chen4Transfercenter Sustainable Electrochemistry, Saarland University and KIST Europe, 66125, Saarbrücken, Germany; State Key Laboratory of Chem/Bio-Sensing and Chemometrics College of Chemistry and Chemical Engineering Hunan University, Changsha, 410082, Hunan, China; Corresponding author.Transfercenter Sustainable Electrochemistry, Saarland University and KIST Europe, 66125, Saarbrücken, GermanyCollege of Materials Science and Engineering Changsha University of Science and Technology, Changsha, 410114, Hunan, ChinaState Key Laboratory of Chem/Bio-Sensing and Chemometrics College of Chemistry and Chemical Engineering Hunan University, Changsha, 410082, Hunan, China; Corresponding author.Transfercenter Sustainable Electrochemistry, Saarland University and KIST Europe, 66125, Saarbrücken, Germany; Materials Innovation Factory, Department of Chemistry, University of Liverpool, Liverpool, L69 7ZD, United Kingdom; Corresponding author.Aqueous redox-active organic materials-base electrolytes are sustainable alternatives to vanadium-based electrolyte for redox flow batteries (RFBs) due to the advantages of high ionic conductivity, environmentally benign, safety and low cost. However, the underexplored redox properties of organic materials and the narrow thermodynamic electrolysis window of water (1.23 V) hinder their wide applications. Therefore, seeking suitable organic redox couples and aqueous electrolytes with a high output voltage is highly suggested for advancing the aqueous organic RFBs. In this work, the functionalized phenazine and nitroxyl radical with electron-donating and electron-withdrawing group exhibit redox potential of −0.88 V and 0.78 V vs. Ag, respectively, in “water-in-ionic liquid” supporting electrolytes. Raman spectra reveal that the activity of water is largely suppressed in “water-in-ionic liquid” due to the enhanced hydrogen bond interactions between ionic liquid and water, enabling an electrochemical stability window above 3 V. “Water-in-ionic liquid” supporting electrolytes help to shift redox potential of nitroxyl radical and enable the redox activity of functionalized phenazine. The assembled aqueous RFB allows a theoretical cell voltage of 1.66 V and shows a practical discharge voltage of 1.5 V in the “water-in-ionic liquid” electrolytes. Meanwhile, capacity retention of 99.91% per cycle is achieved over 500 charge/discharge cycles. A power density of 112 mW cm−2 is obtained at a current density of 30 mA cm−2. This work highlights the importance of rationally combining supporting electrolytes and organic molecules to achieve high-voltage aqueous RFBs.http://www.sciencedirect.com/science/article/pii/S2468025722001364Aqueous redox flow batteriesWater-in-ionic liquid electrolytesHigh-voltage aqueous batteriesOrganic redox-active materials |
| spellingShingle | Zhifeng Huang Rolf Hempelmann Yiqiong Zhang Li Tao Ruiyong Chen Pairing nitroxyl radical and phenazine with electron-withdrawing/-donating substituents in “water-in-ionic liquid” for high-voltage aqueous redox flow batteries Green Energy & Environment Aqueous redox flow batteries Water-in-ionic liquid electrolytes High-voltage aqueous batteries Organic redox-active materials |
| title | Pairing nitroxyl radical and phenazine with electron-withdrawing/-donating substituents in “water-in-ionic liquid” for high-voltage aqueous redox flow batteries |
| title_full | Pairing nitroxyl radical and phenazine with electron-withdrawing/-donating substituents in “water-in-ionic liquid” for high-voltage aqueous redox flow batteries |
| title_fullStr | Pairing nitroxyl radical and phenazine with electron-withdrawing/-donating substituents in “water-in-ionic liquid” for high-voltage aqueous redox flow batteries |
| title_full_unstemmed | Pairing nitroxyl radical and phenazine with electron-withdrawing/-donating substituents in “water-in-ionic liquid” for high-voltage aqueous redox flow batteries |
| title_short | Pairing nitroxyl radical and phenazine with electron-withdrawing/-donating substituents in “water-in-ionic liquid” for high-voltage aqueous redox flow batteries |
| title_sort | pairing nitroxyl radical and phenazine with electron withdrawing donating substituents in water in ionic liquid for high voltage aqueous redox flow batteries |
| topic | Aqueous redox flow batteries Water-in-ionic liquid electrolytes High-voltage aqueous batteries Organic redox-active materials |
| url | http://www.sciencedirect.com/science/article/pii/S2468025722001364 |
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