In conventional batteries which store energy in solid materials, the active materials are coated on current collector in order for good electrical contact with the electrode (current collector). Based on the “redox targeting” reactions of solid energy storage materials with redox mediators, the active material can be reversibly oxidized and reduced without being attached to the current collector. The transport of electrons between the material and the current collector is mediated by the diffusion of redox molecules dissolved in the electrolyte. The application of redox targeting reactions to both the anode and cathode intuitively leads to a novel energy storage device — redox targeting-based flow battery. Insuch a new battery configuration, the active materials are stored statically in two separate tanks and power is produced in the cell stack by the redox reactions of redox mediators, disruptively changing the operation mode of the conventional batteries. Redox targeting-based flow batteryis poised to have advantages over other types of electrochemical energy storage devices in terms of energy density, safety, and operation flexibility for large-scale stationary energy storage. Various redox targeting-based battery systems have been demonstrated since the first report in 2013.1 The battery chemistry has been extended with charge balancing ions from lithium-ion to sodium-ion and proton, electrolytes from non-aqueous to aqueous2, and redox mediators from dual to single redox molecule3.
In this talk, I will report the latest progress on the development of redox targeting-based flow battery, with special focus on the visualization and kinetics of the redox targeting reactions between organic redox species with the energy storage materials.
1. Q. Huang, H. Li, M. Grätzel, and Q. Wang, Reversible Chemical Delithiation/Lithiation of LiFePO4: Towards A Redox Flow Lithium-ion Battery. Phys. Chem. Chem. Phys., 15 (6), 1793-1797 (2013).
2. J. Yu, L. Fan, R. Yan, M. Zhou, and Q. Wang, A Redox Targeting-based Aqueous Redox Flow Lithium Battery. ACS Energy Lett., 3, 2314-2320 (2018).
3. M. Zhou, Q. Huang. T. N. P. Truong, J. Ghilane, Y. G. Zhu, C. Jia, R. Yan, L. Fan, H. Randriamahazaka, Q. Wang, Nernstian Potential-driven Redox Targeting Reactions of Battery Materials. Chem, 3 (6), 1036-1049 (2017).