The use of nickel complexes utilizing non-innocent ligands based on picolinamide to functiona sr edox carriers in flow batteries was explored. The picolinamidem oiety was linked together with ÀCH 2 CH 2 À (bpen), ÀCH 2 CH 2 CH 2 À (bppn), and ÀC 6 H 4 À (bpb) moieties, resulting in two, three, and four quasireversible waves, respectively,f or the nickel complexes and > 3V differenceb etween the outermost positivea nd negative waves. Ther edox events were theoretically modelled for each complex, showinge xcellent agreement (< 0.3 Vd ifference)b etween the experimental and modelled potentials. Bulk cycling of the most soluble complex, Ni(bppn), indicated only one of the three waves was reversible. Therefore, Ni(bppn) has the ability to act as an egative charge redox carrier in flow cells.Although lithium ion batteries tend to dominate the headlines, grid-scale energy storagew ill be served by av ariety of technologies depending on the time period of service. [1] For several decades, one technology attractive for > 4h of discharge is the redox flow battery (RFB, Figure 1). In contrastt os econdary batteries, in which the energy is stored within stationarye lectrodes, RFBs store and release energy from ar edox reaction between soluble chemical species, called redox carriers. At ypical non-hybrid RFB design has two storage tanks for the redox carriers that can be scaled independently of the cell, thereby imparting greater flexibility than as econdary battery,i nw hich power and energy are coupled( Figure1). Aqueousv anadium RFBs are the most developed technology availabley et suffer from the high cost of precursors (vanadium) and low stored energy density.D emand for improvements in energy storage has seen RFB research explode with significant advances: [2] greatly improved vanadium RFBc apacities, [3] identification of
Redox flow batteries (RFBs) have recently been recognized as a potentially viable technology for scalable energy storage. To take full advantage of RFBs, one possible approach for achieving high energy densities is to maximize a number of redox events by utilizing charge carriers capable of multiple one-electron transfers within the electrochemical window of solvent. However, past efforts to develop more efficient electrolytes for nonaqueous RFBs have mostly been empirical. In this manuscript, we shed light on design principles by theoretically investigating the effects of systematically substituting pyridyl moieties with imine ligands within a series of Fe complexes with some experimental validation. We found that such replacement is an effective strategy for reducing the molecular weight-to-charge ratios of these complexes. Simultaneously, calculations suggest that the reduction potentials and ligand-based redox activity of such substituted N-heterocyclic Fe compounds might be maintained within their +4 → −1 charge states. Additionally, by theoretically examining the role of coordination geometry, vis-à-vis reducing the number of redox noninnocent ligands within the first coordination sphere, we have demonstrated that Fe complexes with one such ligand were also capable of supporting multielectron reduction events and exhibited reduction potentials similar to their parent analogs supported by two or three of the same multidentate ligands. However, some differences in redox nature within the lower (+2 → −1) charge states were also noticed. Specifically, complexes containing two bidentate ligands, or one tridentate ligand, exhibited ligand-based reductions, whereas compounds with one bidentate ligand exhibited metal-centered reductions. The current results pave the way toward the design of the next-generation of Fe complexes with lower molecular weights and greater stored energy for redox flow batteries.
No abstract
Redox flow batteries are an attractive solution to the problem of grid-level energy storage however low energy densities and high costs are preventing them from becoming commercially viable on a large-scale. A promising approach to address low energy density is the utilization of non-aqueous solvents, assuming well designed charge carriers can utilize the wider potential window and be sufficiently soluble. In this presentation, we will detail the preparation, characterization, and electrochemical performance of metal complexes with polypyridyl ligands along with preliminary results from a bench-scale flow battery system.
The Cover Feature shows the interaction between theory and experiment that was used to identify prospective redox carriers for a flow battery. More information can be found in the Communication by T. Chu and I. A. Popov et al on page 1304 in Issue 7, 2019 (DOI: 10.1002/cssc.201802985).
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.