Electrolytic molecule in-pore structure and capacitance of supercapacitors with nanoporous carbon electrodes: A coarse-grained molecular dynamics study

Abstract

It has been previously reported that a supercapacitor with activated carbon (AC)-based electrodes has a high degree of nanoporosity and a large specific surface area, leading to a larger capacitance than one using conventional materials for its electrodes. This study investigates the diffusive behavior of organic electrolyte molecules in activated carbon electrodes with different pore sizes and densities using the coarse-grained molecular model and constant-potential molecular dynamics (MD) simulation. This organic electrolyte consists of the tetraethylammonium cation (NEt4+) and tetrafluoroborate anion (BF4−) dissolved in an acetonitrile (ACN) solvent. Combining the time-stamped force-bias Monte Carlo (tfMC) and simulated-annealing methods, AC electrodes with different densities and pore sizes were constructed. This study provides an atomistic scale understanding for the ion exchange mechanism between the nanoporous electrode and electrolyte region. The simulation results were also used for comparison to the graphite electrode supercapacitors of our previous study.