Journal
JOURNAL OF POWER SOURCES
Volume 547, Issue -, Pages -Publisher
ELSEVIER
DOI: 10.1016/j.jpowsour.2022.232007
Keywords
Energy storage system; Zn -Br redox Flow battery; Bromine complexing agent; Steric hindrance; Zinc plating uniformity
Funding
- Korea Institute of Energy Technol- ogy Evaluation and Planning [20224000000020, 20012884]
- Ministry of Trade, Industry & Energy (MOTIE) of the Republic of Korea
- Korea Evaluation Institute of Industrial Technology (KEIT) [20224000000020, 20012884] Funding Source: Korea Institute of Science & Technology Information (KISTI), National Science & Technology Information Service (NTIS)
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In this paper, a new bromine-complexing agent (DMEIm center dot Br) is introduced and its effectiveness in improving the performance of zinc-bromine redox flow batteries is demonstrated. The DMEIm center dot Br enhances the reaction kinetics and reversibility of the Zn2+/Zn((s)) and Br-/Br-2 redox couples, leading to higher current and voltaic efficiencies as well as improved discharge-capacity retention.
In zinc-bromine redox flow batteries (ZBBs), the weak molecular structure and stability of bromine-complexing agent (BCA) can sometime negatively affect battery's performance. To address this issue, this paper introduces a 1,2-dimethyl-3-ethylimidazolium bromide (DMEIm center dot Br, C7H13BrN2), comprising planar molecular structure with strong molecular-polarizability and low steric hindrance. The effectiveness of the DMEIm center dot Br is compared and verified with those of two popular BCAs through various electrochemical experiments including full-cell tests for 200 cycles. Experimental results show that the DMEIm center dot Br significantly contributes to apparently enhancing reaction kinetics and reversibility of Zn2+/Zn((s) )and Br-/Br-2 redox couples by inducing highly reversible zinc-plating/stripping (by strong electrostatic shielding effect) and bromine-capture/release (along with strong bromine-binding strength) in anolyte and catholyte solutions, respectively. The superior chemical and electro-chemical properties are clearly demonstrated by the fact that the DMEIm center dot Br-supported solution in ZBBs exhibits 5.53 (24.19) and 7.29 (16.99) % higher current and voltaic efficiencies than the pristine solution at the tem-perature of 25 (60) ?C, respectively. It also exhibits remarkably improved discharge-capacity retention of averagely 99.17% for 200 cycles along with a slight discharge-capacity loss of only 1.46% vs. 1st cycle at 200th cycle, even at the high temperature of 60 ?C.
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