Redox Flow Batteries (RFBs)

The utilization of intermittent renewable energy sources needs low-cost, reliable energy storage systems in the future. Among various electrochemical energy storage systems, RFBs are promising with merits of independent energy storage and power generation capability, localization flexibility, high efficiency, low scaling-up cost, and excellent long charge/discharge cycle life. RFBs typically use metal ions as reacting species. The most exploited types are all-vanadium RFBs. To enhance the energy storage capability of RFBs, it is necessary to find alternative energy-dense electrolytes (high concentration of active species and with high cell voltage). Recently, efforts have been devoted to energy storage systems that use low-cost, environmentally safe organic and polymer electrolytes and suspension electrolytes with solid active species. Optimization of the vanadium RFBs and the development of new electrolyte and cell systems for a practical application need to overcome many challenges, including the fundamental understanding of the electrolyte electrochemistry, development of improved electrode materials, and innovation in the critical aspects of cell and stack design.


1. Development of New Electrolytes for RFBs


"Water-in-ionic liquid" electrolytes for high voltage aqueous batteries



List of selected publications:

“Water-in-ionic liquid” solutions towards wide electrochemical stability windows for aqueous rechargeable batteries, Y. Zhang, R. Ye, D. Henkensmeier, R. Hempelmann, R. Chen, Electrochimica Acta 263 (2018) 47-52.

Ionic liquid-mediated aqueous redox flow batteries for high voltage applications, R. Chen, R. Hempelmann, Electrochemistry Communications 70 (2016) 56-59.



Ionic modification of redox active organics

List of selected publications:

One-step cationic grafting of 4-hydroxy-TEMPO and its application in a hybrid redox flow battery with a crosslinked PBI membrane, Z. Chang, D. Henkensmeier, R. Chen, ChemSusChem 10 (2017) 3193-3197.



Semi-solid flow batteries

Industrial collaboration



2. All Vanadium RFBs


In collaboration with partners – working on the performance improvement of the ion exchange membranes and graphite felt electrodes


Development of a state-of-charge electrochemical sensor