04/29/2026
By Danielle Fretwell

The Francis College of Engineering, Department of Energy Engineering - Renewable, invites you to attend a Doctoral Dissertation Proposal defense by Eylul Ergun titled: Electrolyte as a Design Lever in Redox-Mediated Flow Batteries: Tuning Solid-Mediator Kinetics and Thermodynamics through Cation Identity and Temperature

Candidate Name: Eylul Ergun
Degree: Doctoral
Defense Date: Wednesday, May 13, 2026
Time: 10 a.m. - noon
Location: Perry 415

Committee:

  • Advisor: Ertan Agar, Ph.D./Associate Professor, Mechanical and Industrial Engineering, UMass Lowell
  • John Hunter Mack, Ph.D./Professor, Mechanical and Industrial Engineering, UMass Lowell
  • Fuqiang Liu, Ph.D./Associate Professor, Mechanical and Industrial Engineering, UMass Lowell
  • Derek Hall, Ph.D./Assistant Professor, Mechanical Engineering, Pennsylvania State University

Abstract:
Redox-mediated flow batteries (RMFBs) promise high energy density storage by pairing a dissolved mediator with a solid booster. Yet, the indirect redox reaction between them remains poorly understood, leaving a persistent gap between theoretical and practical capacity. This study tackles that gap directly by treating the electrolyte as an active design lever rather than a passive medium. Using an aqueous ferri/ferrocyanide–Prussian Blue model system with operando ultramicroelectrode voltammetry, the competing reactions at the electrode and in the reservoir are systematically decoupled in real time. Cation identity serves as a coarse-tuning parameter: the booster potential shifts markedly across alkali cations, with only potassium providing the thermodynamic alignment needed for meaningful utilization, while larger hydrated cations introduce lattice distortion and kinetic suppression. Temperature then acts as a fine-tuning lever; moderate heating to 27°C resolves tank reaction limitations and raises booster utilization from 33.7% to 47%, defining both an optimal operating point and an upper thermal boundary. Building on these insights, the following is proposed: a variable-temperature operation protocol that continuously keeps the booster within the mediator's thermodynamic window, extendable to mixed-cation electrolytes and constant current-constant voltage cycling. Together, these findings establish a mechanistic and experimentally grounded framework for the rational design of next-generation RMFB systems for grid-scale energy storage.