title: Evolutionary Design of Low Molecular Weight Organic Anolyte Materials for Applications in Nonaqueous Redox Flow Batteries.
abstract: The integration of renewable energy sources into the electric grid requires low-cost energy storage systems that mediate the variable and intermittent flux of energy associated with most renewables. Nonaqueous redox-flow batteries have emerged as a promising technology for grid-scale energy storage applications. Because the cost of the system scales with mass, the electroactive materials must have a low equivalent weight (ideally 150 g/(mol·e(-)) or less), and must function with low molecular weight supporting electrolytes such as LiBF4. However, soluble anolyte materials that undergo reversible redox processes in the presence of Li-ion supports are rare. We report the evolutionary design of a series of pyridine-based anolyte materials that exhibit up to two reversible redox couples at low potentials in the presence of Li-ion supporting electrolytes. A combination of cyclic voltammetry of anolyte candidates and independent synthesis of their corresponding charged-states was performed to rapidly screen for the most promising candidates. Results of this workflow provided evidence for possible decomposition pathways of first-generation materials and guided synthetic modifications to improve the stability of anolyte materials under the targeted conditions. This iterative process led to the identification of a promising anolyte material, N-methyl 4-acetylpyridinium tetrafluoroborate. This compound is soluble in nonaqueous solvents, is prepared in a single synthetic step, has a low equivalent weight of 111 g/(mol·e(-)), and undergoes two reversible 1e(-) reductions in the presence of LiBF4 to form reduced products that are stable over days in solution.
authors.affiliation: Joint Center for Energy Storage Research , Argonne, Illinois 60439, United States.|Department of Chemistry, University of Michigan , 930 North University Avenue, Ann Arbor, Michigan 48109, United States.
authors.forename: Christo S
authors.initials: CS
authors.lastname: Sevov
authors.affiliation: Joint Center for Energy Storage Research , Argonne, Illinois 60439, United States.|Department of Chemistry, University of Michigan , 930 North University Avenue, Ann Arbor, Michigan 48109, United States.
authors.forename: Rachel E M
authors.initials: RE
authors.lastname: Brooner
authors.affiliation: Joint Center for Energy Storage Research , Argonne, Illinois 60439, United States.|Department of Chemistry, University of Illinois at Urbana-Champaign , Urbana, Illinois 61801, United States.
authors.forename: Etienne
authors.initials: E
authors.lastname: Chénard
authors.affiliation: Joint Center for Energy Storage Research , Argonne, Illinois 60439, United States.|Materials Science Division, Argonne National Laboratory , Argonne, Illinois 60439, United States.
authors.forename: Rajeev S
authors.initials: RS
authors.lastname: Assary
authors.affiliation: Joint Center for Energy Storage Research , Argonne, Illinois 60439, United States.|Department of Chemistry, University of Illinois at Urbana-Champaign , Urbana, Illinois 61801, United States.|Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign , Urbana, Illinois 61801, United States.
authors.forename: Jeffrey S
authors.initials: JS
authors.lastname: Moore
authors.affiliation: Joint Center for Energy Storage Research , Argonne, Illinois 60439, United States.|Department of Chemistry, University of Illinois at Urbana-Champaign , Urbana, Illinois 61801, United States.
authors.forename: Joaquín
authors.initials: J
authors.lastname: Rodríguez-López
authors.affiliation: Joint Center for Energy Storage Research , Argonne, Illinois 60439, United States.|Department of Chemistry, University of Michigan , 930 North University Avenue, Ann Arbor, Michigan 48109, United States.
authors.forename: Melanie S
authors.initials: MS
authors.lastname: Sanford