Abstract
Due to their almost unlimited scalability, redox flow batteries can make versatile and affordable energy storage systems. Redox active materials (redoxmers) in these batteries largely define their electrochemical performance, including the life span of the battery that depends on the stability of charged redoxmers. In this study, we examine the effects of expanding the π-system in the arene rings on the chemical stability of dialkoxyarene redoxmers that are used to store positive charge in RFBs. When 1,4-dimethoxybenzene is π-extended to 1,4-dimethoxynaphthalene, a lower redox potential, improved kinetic stability, and longer cycling life are observed. However, when an additional ring is fused to make 9,10-dimethoxyanthracene, the radical cation undergoes rapid O-dealkylation possibly due to increased steric strain that drives methoxy out of the arene plane thus breaking the π-conjugation with O 2p orbitals. On the other hand, the planar structure of 1,4-dimethoxynaphthalene may facilitate second-order reactions of radical cations leading to their neutralization in the bulk. Our study suggests that extending the π-system changes reactivity in multiple (sometimes, opposite) ways, so lowering the oxidation potential through π-conjugation to improve redoxmer stability should be pursued with caution.
| Original language | English |
|---|---|
| Article number | 234689 |
| Journal | Journal of Power Sources |
| Volume | 608 |
| DOIs | |
| State | Published - Jul 15 2024 |
Funding
This work was partially supported by the Joint Center for Energy Storage Research (JCESR), an Energy Innovation Hub funded by the U.S. Department of Energy, Office of Science, Basic Energy Sciences. The authors also thank financial support from the U.S. National Science Foundation (Award No. CHE-2055222) and from the U.S. Department of Energy, Office of Science, Small Business Innovation Research (Award No. 077040-00002B). The submitted manuscript has been created by UChicago Argonne, LLC, Operator of Argonne National Laboratory (\u201CArgonne\u201D). Argonne, a U.S. Department of Energy Office of Science laboratory, is operated under Contract No. DE-AC02-06CH11357. The U.S. Government retains for itself, and others acting on its behalf, a paid-up nonexclusive, irrevocable worldwide license in said article to reproduce, prepare derivative works, distribute copies to the public, and perform publicly and display publicly, by or on behalf of the Government. This work was partially supported by the Joint Center for Energy Storage Research (JCESR), an Energy Innovation Hub funded by the U.S. Department of Energy, Office of Science, Basic Energy Sciences. The authors also thank financial support from the U.S. National Science Foundation (Award No. CHE-2055222) and from the U.S. Department of Energy, Office of Science, Small Business Innovation Research (Award No. 077040-00002B). The submitted manuscript has been created by UChicago Argonne, LLC, Operator of Argonne National Laboratory (\"Argonne\"). Argonne, a U.S. Department of Energy Office of Science laboratory, is operated under Contract No. DE-AC02-06CH11357. The U.S. Government retains for itself, and others acting on its behalf, a paid-up nonexclusive, irrevocable worldwide license in said article to reproduce, prepare derivative works, distribute copies to the public, and perform publicly and display publicly, by or on behalf of the Government.
Keywords
- Nonaqueous redox flow battery
- Ring fusion
- Stability
- Steric strain
- organic redox molecules