Invited Talk: Development of Nonaqueous Redox Flow Battery Technologies

Abstract

Nonaqueous redox flow batteries are generally considered to have higher energy densities than their aqueous counterparts because of their wider voltage windows. However, their performance has lagged far behind their inherent capability due to the combined limitations of redox chemistry, solubility of redox species, and cell design. Here we report a high-performance nonaqueous lithium–organic redox flow battery with a structure-modified ferrocene cathode. The ionic-liquid derivatization of ferrocene increases the solubility by more than 20 times in the supporting electrolyte (0.85 M as opposed to 0.04 M for pristine ferrocene). This improvement is confirmed by solvation chemistry studies through nuclear magnetic resonance analysis and density functional theory calculation. When coupled with a lithium-graphite hybrid anode, the flow battery exhibits a cell voltage of 3.49 V and energy efficiency over 75% (Figure 1). The method of material modification proved to be a viable way to prepare high-performance electrolyte for nonaqueous redox flow batteries.Development on the total-organic redox flow battery will also be presented. Acknowledgements The authors would like to acknowledge financial support primarily from the U.S. Department of Energy’s (DOE’s) Office of Electricity Delivery and Energy Reliability (OE) (under Contract No. 57558) and the support from Laboratory-Directed Research and Development Program (LDRD) of the Pacific Northwest National Laboratory (PNNL). The NMR characterization was supported as part of the Joint Center for Energy Storage Research, an Energy Innovation Hub funded by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, and was conducted in the William R. Wiley Environmental Molecular Sciences Laboratory (EMSL), a national scientific user facility sponsored by DOE’s Office of Biological and Environmental Research and located at PNNL. PNNL is a multi-program national laboratory operated by Battelle for DOE under Contract DE-AC05-76RL01830.