High performance and long cycle life neutral zinc-iron flow batteries enabled by zinc-bromide complexation

Autor: Weizhe Xiang, Guangmin Zhou, Runhua Gao, Minghui Yang, Liangyu Li, Mei Ding, Chuankun Jia, He Xu, Zhizhao Xu, Ao Tang
Rok vydání: 2022
Předmět:
Zdroj: Energy Storage Materials. 44:433-440
ISSN: 2405-8297
DOI: 10.1016/j.ensm.2021.10.043
Popis: 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 couples. 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 characterization and density functional theory calculation verify that the formation of Zn[Brn(H2O)6-n]2-n (1≤n≤4, n is integer.) ions accounts for the increased electrochemical reversibility of Zn/Zn2+ pairs. 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 hours), shedding light on their great potential for large scale energy storage.
Databáze: OpenAIRE
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