Impact of Ion Geometry and Electrode Pore Interconnectivity on Charge Storage and Dynamics in Confined Nanopores

ABSTRACT Climate change and global targets to achieve net‐zero carbon goals need efficient energy storage systems that are capable of powering green mobility and have the capacity to mitigate the irregular supply of renewable sources. Among the various available technologies, energy storage devices such as batteries, supercapacitors, etc., provide a sustainable solution. However, these devices currently lack the required performance to meet the growing demands, particularly in terms of power and energy densities, fast charging capabilities, longer cycle life, etc. Their electrochemical performance is mainly determined by how many electrolyte ions are stored within the electrodes without the crowding effect. The shape and size of electrolyte ions, along with electrode pore connectivity, are two major factors that significantly affect charge storage capabilities. Determining these relations using traditional experimental methods is time‐consuming, expensive, complex, and ineffective. Hence, this study uses molecular dynamics simulation integrated with density functional theory calculations to gain insights into how ion shape and size affect the charge storage mechanism. Further, the significance of electrode pore interconnectivity in governing charge storage is also explored in this work. The study employed a microporous carbon electrode with a pore size distribution ranging from ∼0.3 to 1.0 nm. Results indicate that [EMIM] + (∼0.76 × 0.43 nm) with [Cl] − (∼0.18 nm) is significantly smaller than [C 4 C 1 Pyrr] + (∼1.10 × 0.60 nm) and [TFSI] − (∼0.79 × 0.29 nm). Further, the ionic size of [EMIM] + /[Cl] − fall within the pore size distribution and was thus diffuse more readily and yield higher in‑pore ion counts and charge storage. Bulkier ions like [C 4 C 1 Pyrr] + and [TFSI] − systems were found to be locally concentrated near the initial sections of the electrode, partly due to their large size and/or due to their shape. Density functional theory studies also support the results obtained from molecular dynamics simulations and confirm that smaller ions whose size falls within the electrode pore size distribution contribute to double‐layer formation and thereby aid in improving the charge storage of energy storage devices.