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arXiv · 1512.00882

Theory of phase separation and polarization for dissociated ionic liquids

Nir Gavish·Arik Yochelis
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Abstract

Room temperature ionic liquids are attractive to numerous applications and particularly, to renewable energy devices. As solvent free electrolytes, they demonstrate a paramount connection between the material morphology and Coulombic interactions: unlike dilute electrolytes, the electrode/RTIL interface is a product of both electrode polarization and spatiotemporal bulk properties. Yet, theoretical studies have dealt almost exclusively with independent models of morphology and electrokinetics. In this work, we develop a novel Cahn-Hilliard-Poisson type mean-field framework that couples morphological evolution with electrokinetic phenomena. Linear analysis of the model shows that spatially periodic patterns form via a finite wavenumber instability, a property that cannot arise in the currently used Fermi-Poisson-Nernst-Planck equations. Numerical simulations in above one-space dimension, demonstrate that while labyrinthine type patterns develop in the bulk, stripe patterns emerge near charged surfaces. The results qualitatively agree with empirical observations and thus, provide a physically consistent methodology to incorporate phase separation properties into an electrochemical framework.

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Nir Gavish, Arik Yochelis. 2015-12-17. Theory of phase separation and polarization for dissociated ionic liquids. https://doi.org/10.1021/acs.jpclett.6b00370

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