Abstract

Being the most potential battery candidate for the electrical grids connections due to having promising electrochemical energy storing abilities, vanadium redox flow battery (VRFB) is widely recognized state-of-the-art technology in renewable energy sectors. Despite its uniqueness of utilizing "all-vanadium" redox couples as the most prospective electrolyte materials, and their conspicuous technological functionalizations, the research works concentrated into its internal operational mechanisms of the cell at both ideal & different state-of-charges are still in the primitive stage. This MD simulation based theoretical insights aiming at revealing benchmark quantitative information on the interfacial micro structures around its Nafion-117 type proton exchange membrane, the intense hydration affinities of its adjacent state bare Vn+ ions, and the closed proximity around the H2O, H3O+, & Nafion-SO3-, etc. at nanometer scale would be a stepping-stone to its technological advancement. The general results presented here illuminate that the VRFB-electrolyte hosting H2O molecules and protons in Hydronium (H3O+), Eigen (H5O2+), & Zundel (H9O3+) states are distributed in a pattern identical to that in a purely bulk water system, and are dynamically used up for exhibiting facile proton conduction. Besides this, the significant departures of the SO3- units of the Nafion-117 at water content (l) = 22 predicted herein confirms its experimentally observed feature of easy accommodating H2O, H3O+, & Vn+ in between them; elucidating the reasons behind its atypical proton conductivity & ionic mobility rates under wet conditions. The MD trajectories based radial distribution function (RDF) predicted Vn+- OH2 radial distances validate the extreme hydration affinities of the bare adjacent Vn+ ions plus their stabilizing propensities with free H2O molecules as established earlier by the DFT based quantum mechanical method.

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