Résumé
Electrochemical double layer capacitors, often called supercapacitors, are energy storage systems which accumulate and release energy through reversible ion adsorption at electrode/electrolyte interfaces. Porous carbons are commonly used as electrode materials due to their relatively low cost and good electronic conductivity. Over the past decade, most of the simulations of supercapacitors were performed at the microscopic scale, using Molecular Dynamics (MD) simulations. This allowed to understand the adsorption of ions and the effect of surface porosity on some electrochemical properties. However it is well known from experiments that commercial materials are highly inhomogeneous, while molecular simulations, where electrode sizes are a few nanometers, only allow for the inclusion of a few pores. It is therefore necessary to simulate electrodes and supercapacitors at larger scales.To this end, we develop a software, Lattice Porous Carbon 3D (LPC3D), designed for mesoscopic simulations of capacitive properties of carbon-carbon capacitors, based on a lattice-gas model. The code calculates properties such as quantities of adsorbed ions, diffusion coefficients and Nuclear Magnetic Resonance (NMR) spectra for ions adsorbed in porous carbons. I will show how the mesoscopic model allows to bridge the gap between the time and length scales of atomistic simulations, accurate but computationally expensive, and experimental results such as electrochemical measurements and nuclear magnetic resonance spectroscopy. I will then describe how the latest code improvements allowed us to simulate systems with length scales up to hundreds to thousands of microns and how we are moving towards coupling LPC3D with molecular simulations codes (molecular DFT and MD simulations) to increase the accuracy of the model. I will also discuss possible perspectives to tackle different types of high power devices.