期刊
ENERGY STORAGE MATERIALS
卷 44, 期 -, 页码 433-440出版社
ELSEVIER
DOI: 10.1016/j.ensm.2021.10.043
关键词
Zn/Fe flow batteries; Electrochemical energy storage; Electrolyte additive; Redox reversibility; Complexation interaction
资金
- 100 Talented Team of Hunan Province [[2016] 91]
- Huxiang High-level talents programs [2018RS3077, 2019RS1046]
- Natural Science Foundation of Hunan Province [2020JJ5566]
- Open Fund of National Engineering Laboratory of Highway Maintenance Technology (Changsha Univeristy of Science Technology) [kjf170105]
- National Key Research and Development Program of China [2019YFA0705700]
- National Natural Science Foundation of China [52072205]
- Shenzhen Geim Graphene Center
Zinc-based flow batteries with bromide ions as stabilizers show improved redox reversibility between Zn and Zn2+. The addition of ZnBr2 as an electrolyte additive promotes the coordination interactions between Zn2+ and Br-, enhancing the efficiency and cycling stability of neutral Zn/Fe flow batteries for large-scale energy storage.
Zinc-based flow batteries have attracted tremendous attention owing to their outstanding advantages of high theoretical gravimetric capacity, low electrochemical potential, rich abundance, and low cost of metallic zinc. Among which, zinc-iron (Zn/Fe) flow batteries show great promise for grid-scale energy storage. However, they still face challenges associated with the corrosive and environmental pollution of acid and alkaline electrolytes, hydrolysis reactions of iron species, poor reversibility and stability of Zn/Zn2+ redox couple. In this work, bromide ions are used to stabilize zinc ions via complexation interactions in the cost-effective and eco-friendly neutral electrolyte. Cyclic voltammetry results reveal that the redox reversibility between Zn and stabilized Zn2+ is greatly improved. The results of spectrum characterizations and density functional theory calculations verify that the formation of Zn[Br-n(H2O)(6-n)](2-n) (1 <= n <= 4, n is integer.) ions accounts for the increased electrochemical reversibility of Zn/Zn2+ pair. Moreover, to overcome the bottleneck of slow kinetics of the coordination interactions between Zn2+ and Br-, ZnBr2 is judiciously selected as the electrolyte additive to promote the complexation process. Adopting K3Fe(CN)(6) as the positive redox species to pair with the zinc anode with ZnBr2 modified electrolyte, the proposed neutral Zn/Fe flow batteries deliver excellent efficiencies and superior cycling stability over 2000 cycles (356 h), shedding light on their great potential for large scale energy storage.
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