Simulating Supercapacitors: Can We Model Electrodes As Constant Charge Surfaces?

Céline Merlet (1, 2) , Clarisse Péan (2, 1, 3) , Benjamin Rotenberg (2, 1) , Paul A Madden (4) , Patrice Simon (2, 3) , Mathieu Salanne (2, 1)

1 PECSA - Physicochimie des Electrolytes, Colloïdes et Sciences Analytiques
2 RS2E - Réseau sur le stockage électrochimique de l'énergie
3 CIRIMAT - Centre interuniversitaire de recherche et d'ingenierie des matériaux
4 University of Oxford

Supercapacitors based on an ionic liquid electrolyte and graphite or nanoporous carbon electrodes are simulated using molecular dynamics. We compare a simplified electrode model in which a constant, uniform charge is assigned to each carbon atom with a realistic model in which a constant potential is applied between the electrodes (the carbon charges are allowed to fluctuate). We show that the simulations performed with the simplified model do not provide a correct description of the properties of the system. First, the structure of the adsorbed electrolyte is partly modified. Second, dramatic differences are observed for the dynamics of the system during transient regimes. In particular, upon application of a constant applied potential difference, the increase in the temperature, due to the Joule effect, associated with the creation of an electric current across the cell follows Ohm's law, while unphysically high temperatures are rapidly observed when constant charges are assigned to each carbon atom.

Mots clés: electrolyte; graphite; molecular dynamics; nanoporous carbon electrode; supercapacitor

Domaines: Chimie théorique et/ou physique; Matériaux

Céline Merlet, Clarisse Péan, Benjamin Rotenberg, Paul A Madden, Patrice Simon, et al.. Simulating Supercapacitors: Can We Model Electrodes As Constant Charge Surfaces?. Journal of Physical Chemistry Letters, 2013, 4 (2), pp.264-268. ⟨10.1021/jz3019226⟩. ⟨hal-00854038⟩