(485b) Leveraging Ion Confinement in Porous Carbon Nanomaterials for Rapid Energy Storage

Low-dimensional carbon materials, such as graphene and nanoporous carbon, have become increasingly prominent for use as electrodes in electrochemical double layer capacitors, owing to their high specific and volumetric surface area and good electrical conductivity. However, recent experiments report a widely-scattered array of capacitive performances, both anomalously large and modest, when nanopore sizes approach the diameter of electrolyte ions. Atomistic insights from molecular simulations of the electrode/electrolyte interface can help provide materials design principles for better and more reliable performance through an improved understanding of the fundamental charge storage behavior. To this end, we use voltammetric molecular dynamics simulations to explore the non-equilibrium processes associated with extreme confinement of ionic liquid electrolytes within subnanometer pores. We present a mechanistic perspective centered around ion reorganization kinetics and specifically reveal the dependence of ion migration efficiency, and relatedly, the capacitance, on pore morphology. We also introduce a simple structural descriptor called the pore shape factor and demonstrate its potential for materials optimization.