On the development of an original mesoscopic model to predict the capacitive properties of carbon-carbon supercapacitors.

We report on the development of a lattice model to predict structural, dynamical and capacitive properties of electrochemical double layer capacitors. The model uses input from molecular simulations, such as free energy profiles to describe the ion adsorption, and experiments, such as energy barriers for transitions between lattice sites. The model developed is approximately 10,000 times faster than common molecular simulations. We apply this model to a set of carbon structures with well-defined pore sizes and investigate the solvation effect by doing simulations with neat ionic liquids as well as acetonitrile-based electrolytes. We show that our model is able to predict quantities of adsorbed ions and capacitances in a range compatible with experimental values. We show that there is a strong dependency of the calculated properties on the pore size and on the presence or absence of solvent. In particular, for neat ionic liquids, larger capacitances are obtained for smaller pores, while the opposite trend is observed for organic electrolytes. Image 1 • A mesoscopic model to predict quantities of adsorbed ions and capacitances of porous carbons has been developed. • As a charging mechanism, ionic exchange is enhanced in porous carbons with small pores. • Addition of solvent in the electrolyte improves the ionic exchange mechanism. • Carbon electrodes store more ionic charge at the interface with neat ionic liquids. • Higher capacitance is obtained when combining neat ionic liquids with small pores or organic electrolytes with large pores. [ABSTRACT FROM AUTHOR]