Abstract
Redox-targeted flow batteries (RTFBs) are promising for large-scale energy storage but suffer from poor solid booster utilization. This study examines how binder selection affects the reaction rate between a LiFePO(4)/FePO(4) solid booster composite and a dissolved [Fe-(CN)(6)](4-/3-) redox mediator. The porosity and hydrophilicity of LiFePO(4) composites correlate with booster utilization, determined by galvanostatic cell cycling and by in situ UV-Vis spectroscopy. Compared with state-of-the-art polyvinylidene difluoride composites, booster pellets containing non-fluorinated, biodegradable polycaprolactone or cellulose acetate binders exhibit up to 175% higher LiFePO(4) conversion rates and improved capacity utilization at cycling rates up to 10 mA cm(-2). Solid-material utilization directly correlates with binder hydrophilicity, establishing it as a key design parameter for RTFBs and offering a straightforward path toward more efficient and non-fluorinated booster formulations.