Journal
ACS APPLIED MATERIALS & INTERFACES
Volume 12, Issue 39, Pages 43568-43575Publisher
AMER CHEMICAL SOC
DOI: 10.1021/acsami.0c09941
Keywords
radical charge population; radical energy; N-acetyl substituent; piperidine nitroxyl radical; zinc hybrid AFBs
Funding
- National Natural Science Foundation of China [21875181, 51802256]
- Natural Science Basic Research Program of Shaanxi [2019JLP-13]
- Shaanxi Key Research and Development Project [2019TSLGY07-05]
- 111 Project 2.0 [BP2018008]
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Redox-active 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) derivatives have recently been investigated to expand the choice of catholyte for aqueous flow batteries (AFBs). However, the effects of substituent R in 4-position on redox potential and corresponding capacity fading mechanism are still unclear. Here, we conduct comparative studies of four R-TEMPO with R = -OH, -NH2, -COOH, and -NHCOCH3 in zinc hybrid AFBs. Experimental and theoretical analyses reveal that low-radical head charge population sum and radical energy, depending on R in 4-position, play a critical role in enhancing redox potential and cycling life of R-TEMPO. The electronic effect brought along by N-acetyl could redistribute the charge and lower systematic energy, making the ring-opening joint sturdy and therefore suppress the side reactions. Accordingly, the 4-NHCOCH3-TEMPO/Zn battery achieves a high capacity retention of >99.65%/day and an open-circuit voltage of 1.71 V. Our findings on the effects of substituent are greatly anticipated to boost the high-energy density, long-life, and eco-friendly TEMPO-based AFBs.
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