Iron-iminopyridine complexes as charge carriers for non-aqueous redox flow battery applications

Journal Article · Mon Feb 01 00:00:00 EST 2021 · Energy Storage Materials

DOI:https://doi.org/10.1016/j.ensm.2021.01.035· OSTI ID:1765877

Gordon, John Cameron  ^[1]; Sharma, Shikha  ^[1]; Andrade, Gabriel A.  ^[1]; Maurya, Sandipkumar  ^[1]; Popov, Ivan Aleksandrovich  ^[1]; Batista, Enrique Ricardo  ^[1]; Davis, Benjamin L.  ^[1]; Mukundan, Rangachary  ^[1]; Smythe, Nathan C.  ^[1]; Tondreau, Aaron M.  ^[1]; Yang, Ping  ^[1]

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1. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

Non-aqueous redox flow batteries (RFBs) have been gaining increased attention in the energy storage arena. Some of their attractive features include the promise for high energy densities, wider voltage windows compared to aqueous systems, as well as wider operating temperature ranges. One of the major challenges in the development of these systems is the lack of electroactive materials that can undergo reversible redox events within the larger potential window of organic solvents. In this paper, we present the design, synthesis, and measurement of electrochemical properties of some iron-based imine- and iminopyridine complexes as promising candidates for RFB applications. Synthesized complexes afforded three reversible redox couples over a ~3 V range. The redox events were also computationally explored and are in good agreement with experimental data. Theoretical calculations show that the redox event at the positive potential can be characterized as metal-centered event corresponding to Fe³⁺ → Fe²⁺ reduction, while the two redox events at negative potentials are associated with the consecutive reductions of iminopyridine or diimine moieties. This work has led to the identification of a promising anolyte material, [tris(imino)pyridine)Fe][OTf]₂ (1), which is soluble in acetonitrile and is synthesized in two simple steps. This species shows outstanding performance when cycled between 1.0 V and 2.35 V, with 93% coulombic efficiency, 84% energy efficiency, and a capacity decay rate of 0.61% per cycle at 5 mA cm^–2. Further modifications to this kind of charge carrier may lead to the development of high energy density materials for grid scale energy storage applications.

• Research Organization: Los Alamos National Laboratory (LANL), Los Alamos, NM (United States)
• Sponsoring Organization: USDOE National Nuclear Security Administration (NNSA); USDOE Laboratory Directed Research and Development (LDRD) Program; USDOE Office of Electricity (OE); USDOE Office of Science (SC)
• Grant/Contract Number: 89233218CNA000001; 20170046DR; 2018BU0048; 89233218NCA000001; 2022547; 2022548; 2022549; 2022550
• OSTI ID: 1765877
• Alternate ID(s): OSTI ID: 1809848
• Report Number(s): LA-UR-20-28348
• Journal Information: Energy Storage Materials, Vol. 37, Issue C; ISSN 2405-8297
• Publisher: Elsevier
• Country of Publication: United States
• Language: English

Related Subjects

25 ENERGY STORAGE
inorganic and physical chemistry
organic chemistry
non-aqueous redox flow batteries
iron-imine complexes
charge carriers
renewable energy
energy storage