Redox flow battery (RFB) offers great promise to provide transformational progress for large-scale energy storage technology. As the energy-bearing redox active species are dissolved and externally stored in liquid electrolytes, their physiochemical properties dictate the energy density, specific capacity, and cycle life thereby become a single most critical component of RFB. For instance, the concentration and chemical stability of redox active species within the electrolyte will determine the system-specific energy density and temperature window for the RFB operation, respectively¹. With the growing interest in developing sustainable RFB systems, there is a pressing task to identify the optimal electrolyte. This led to an active search for an ideal electrolyte which can hold a higher concentration of redox active species with wide chemical and thermal stability. Most electrolyte research has been focused on the empirical study of the effects of the pH, additives and solvent composition². Using combined spectroscopic and computational studies we established an electrolyte design formulation based on molecular solvate structure tuning^{3, 4}. This helps us to optimize the solubility and redox potential of redox molecule, exemplifying a generic electrolyte design strategy for RFB (see Figure 1). In this presentation, we will discuss the virtual screening and electrolyte design procedures for selecting functional moieties, additive salt and co-solvent to enhances the much-needed redox molecule solubility and stability.

References

1. M. Vijayakumar, W. Wang, Z. Nie, V. Sprenkle and J. Hu, Journal of Power Sources 241, 173-177 (2013).
2. M. Vijayakumar, Z. Nie, E. Walter, J. Hu, J. Liu, V. Sprenkle and W. Wang, ChemPlusChem 80 (2), 428-437 (2015).
3. K. S. Han, N. N. Rajput, M. Vijayakumar, X. L. Wei, W. Wang, J. Z. Hu, K. A. Persson and K. T. Mueller, J Phys Chem C 120 (49), 27834-27839 (2016).
4. L. Li, S. Kim, W. Wang, M. Vijayakumar, Z. Nie, B. Chen, J. Zhang, G. Xia, J. Hu, G. Graff, J. Liu and Z. Yang, Advanced Energy Materials 1 (3), 394-400 (2011).