Electric Double Layers At the Interface of Ionic Liquids/Onion-Like Carbon: Capacitance Enhancement Originating From Spherical Curvature

Recent experiments indicate that onion-like carbon (OLCs) can be used as the electrodes in supercapacitors to increase their energy density and charging/discharging rates.[1] To understand the physical origin of such observations, molecular dynamics simulations were performed for an IL of [emim+][TFSI-] near idealized spherical carbon onions. We investigated the structure and capacitance of electrical double layers (EDLs) in ILs outside these OLCs with radii ranging from 0.356 nm – 1.223nm. We quantified the structure of EDLs near the OLCs and computed their capacitance. The scaling of capacitance with respect to the radius of OLC exhibits a qualitative agreement with experimental observations. We attribute the enhancement of capacitance over planar surfaces to the curvature of OLCs.

 [1] D. Pech, M. Brunet, H. Durou, P. Huang, V. Mochalin, Y. Gogotsi, P.L. Taberna and P. Simon, Nature Nanotech. 2010, 5, 651.

* To whom correspondence should be addressed. E-mail: peter.cummings@vanderbilt.edu