Molecular Dynamics Simulations of Electrolyte Solutions for Organic Redox Flow Battery

Organic redox flow batteries (ORFBs) are emerging as promising candidates for sustainable, large scale energy storage applications [1]. A fundamental understanding of electrolyte behavior at the molecular level is essential for improving the performance, stability, and efficiency of these systems [2]. In this work, we employ classical molecular dynamics (MD) simulations to investigate the structural and dynamical properties of electrolyte solutions and their interactions at the electrode/electrolyte interface. Our study follows a systematic, stepwise approach in which individual components and their mixtures are examined. Initially, pure solvents such as acetonitrile and 3-methoxypropionitrile are simulated to characterize their bulk properties and molecular organization. The study is then extended to the ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide (EMIMTFSI), analyzed both in isolation and in combination with the solvents. These simulations provide insights into solvent structure, ion solvation environments, ion pairing, and the effect of solvent composition on electrolyte organization. Simulations are performed using the LAMMPS package [3], employing the non-polarizable OPLS-AA force field [4] for molecular solvents and the CL&P force field for ionic liquids [5]. To approximate electronic polarization effects, a charge scaling factor is applied [6]. In future work, redox-active species will be incorporated to study solvation dynamics and interfacial processes in ORFB systems. [1] Leung, P., et al., Journal of Power Sources, 360, 243-283. (2017). [2] Reeves, K. G., et al., Physical Chemistry Chemical Physics, 22 (19), 10561-10568. (2020). [3] A. P. Thompson, et al., LAMMPS - a flexible simulation tool for particle-based materials modeling at the atomic, meso, and continuum scales., Computer physics communications., 271 , 108171. (2022). [4] Dodda, L. S., et al., Nucleic acids research, Nucleic acids research. 45(W1), W331-W336. (2017). [5] Canongia Lopes, et al., Theoretical Chemistry Accounts,. 131 , 1-11. (2012). [6] Doherty, B., et al., Journal of chemical theory and computation, 13 (12), 6131-6145. (2017). Financial support from the European Union Horizon Europe Research and Innovation programme under the Marie Skłodowska Curie Industrial Doctoral Network [101119913] “StoreAge” is gratefully acknowledged.