Transitioning from vanadium RFBs to non-aqueous systems provides an opportunity to increase the energy density by raising the cell voltage by 2-3-fold through utilizing redox couples that take advantage of the wider electrochemical stability window of aprotic, non-aqueous solvents. Despite this promise, limited solubility of active species, lack of effective membranes, and long term instability of active species (especially in their charged forms) have hindered the progress in the development of non-aqueous redox flow batteries. When building energy dense RFBs, the solubility of redox couples and the cell voltage of the flow cell is critical. However, the stability of the charged forms of redox active species suffers at their extreme redox potentials due to either self-discharge in electrolyte solutions or molecular degradation at their charge forms, presenting a challenge in achieving high cell voltages. In this work, we sought to explore the change of chemical stability, cycling stability, and the electrochemical decay pathways of organic posolytes by considering variably functionalized electron donating redox active organic molecules at different oxidation potentials in different non-aqueous electrolyte systems. This presentation will report the preparation of a series of neutral and charged forms of posolytes, their chemical and cycling stability in non-aqueous solvents/electrolytes, and spectroscopic and electrochemical analysis. <br/><br/>

Comparative study on the chemical and cycling stabilities of redox active organic posolytes with their voltages for non-aqueous redox flow battery applications

2019 Spring National Meeting

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