Abstract
Targeting redox flow batteries (RTFB) are an emerging alternative to traditional redox flow battery architecture which offer improved energy density via an added electroactive solid. This Ph.D. thesis is centered around the screening for iron(III)-organic complexes as negolyte redox mediators in aqueous neutral RTFBs by a dual experimental-computational screening approach. First, iron(III) complexes were characterized using cyclic voltammetry and UV-Visible spectroscopy. Of the synthesized complexes, eight showed quasireversible behavior and were used to identify a suitable DFT protocol for predicting their reduction potentials. The M02-2X/6-311+G(d)/COSMO-RS level of theory yielded the smallest errors, with an MAE of 0.066 V for the initial set of complexes and an MAE of 0.22 V for a generalized set including different metal centers. The cycling behavior of the iron maltolate complex was demonstrated vs. iron hexacyanide. The cell showed good stability when cycled in an N2 glove box with a CE of 99.7% and a capacity decay of 1.9 % per day. The cell had a high internal resistance, as the capacity reversibly faded upon cycling at higher current densities. The stability of both oxidized and reduced species was verified by introducing holds at the end of charge and discharge. Finally, the encapsulation of sodium titanium phosphate using spark-plasma sintering and its ex-situ redox targeting reaction with the iron TIRON complex was explored as a perspective study