Influence of solvation on the structural and capacitive properties of electrical double layer capacitors

Céline Merlet (1, 2) , Mathieu Salanne (1, 2) , Benjamin Rotenberg (1, 2) , Paul A Madden (3)

1 RS2E - Réseau sur le stockage électrochimique de l'énergie
2 PECSA - Physicochimie des Electrolytes, Colloïdes et Sciences Analytiques
3 University of Oxford

We use molecular dynamics simulations to explore the impact of a non-ionic solvent on the structural and capacitive properties of supercapacitors based on an ionic liquid electrolyte and carbon electrodes. The study is focused on two pure ionic liquids, namely 1-butyl-3-methylimidazolium hexafluorophosphate and 1-butyl-3-methylimidazolium tetrafluoroborate, and their 1.5 M solutions in acetonitrile. The electrolytes, represented by coarse-grained models, are enclosed between graphite electrodes. We employ a constant potential methodology which allows us to gain insight into the influence of solvation on the polarization of the electrodes as well as the structural and capacitive properties of the electrolytes at the interface. We show that the interfacial characteristics, different for two distinct pure ionic liquids, become very similar upon mixing with acetonitrile.

Mots clés: Double layer capacitance; Solvation; Molecular dynamics simulations; Interfacial structure; Graphite

Domaines: Chimie théorique et/ou physique; Science des matériaux [cond-mat.mtrl-sci]

Céline Merlet, Mathieu Salanne, Benjamin Rotenberg, Paul A Madden. Influence of solvation on the structural and capacitive properties of electrical double layer capacitors. Electrochimica Acta, 2013, 101, pp.262-271. ⟨10.1016/j.electacta.2012.12.107⟩. ⟨hal-00853396⟩