Dynamic Charge Storage in Ionic Liquids-Filled Nanopores: Insight from a Computational Cyclic Voltammetry Study.
Understanding the dynamic charge storage in nanoporous electrodes with room-temperature ionic liquid electrolytes is essential for optimizing them to achieve supercapacitors with high energy and power densities. Herein, we report coarse-grained molecular dynamics simulations of the cyclic voltammetry of supercapacitors featuring subnanometer pores and model ionic liquids. We show that the cyclic charging and discharging of nanopores are governed by the interplay between the external field-driven ion transport and the sloshing dynamics of ions inside of the pore. The ion occupancy along the pore length depends strongly on the scan rate and varies cyclically during charging/discharging. Unlike that at equilibrium conditions or low scan rates, charge storage at high scan rates is dominated by counterions while the contribution by co-ions is marginal or negative. These observations help explain the perm-selective charge storage observed experimentally. We clarify the mechanisms underlying these dynamic phenomena and quantify their effects on the efficiency of the dynamic charge storage in nanopores.
†Department of Mechanical Engineering, Virginia Tech, Blacksburg, Virginia 24061, United States.
Yadong
Y
He
Jingsong
J
Huang
Bobby G
BG
Sumpter
¶Department of Chemistry, Faculty of Natural Sciences, Imperial College London, SW7 2AZ London, United Kingdom.
Alexei A
AA
Kornyshev
†Department of Mechanical Engineering, Virginia Tech, Blacksburg, Virginia 24061, United States.
Rui
R
Qiao
charging dynamics; cyclic voltammetry; dynamic charge storage; nanopore; room-temperature ionic liquids; supercapacitor