Voltage Dependent Charge Storage Modes and Capacity in Subnanometer Pores.
Using molecular dynamics simulations, we show that charge storage in subnanometer pores follows a distinct voltage-dependent behavior. Specifically, at lower voltages, charge storage is achieved by swapping co-ions in the pore with counterions in the bulk electrolyte. As voltage increases, further charge storage is due mainly to the removal of co-ions from the pore, leading to a capacitance increase. The capacitance eventually reaches a maximum when all co-ions are expelled from the pore. At even higher electrode voltages, additional charge storage is realized by counterion insertion into the pore, accompanied by a reduction of capacitance. The molecular mechanisms of these observations are elucidated and provide useful insight for optimizing energy storage based on supercapacitors.
†Department of Mechanical Engineering, Clemson University, Clemson, South Carolina 29634-0921, United States.
Peng
P
Wu
‡Center for Nanophase Materials Sciences and Computer Science and Mathematics Division, Oak Ridge National Laboratory, Bethel Valley Road, Oak Ridge, Tennessee 37831-6367, United States.
Jingsong
J
Huang
§Department of Physics, Applied Physics, and Astronomy, Rensselaer Polytechnic Institute, Troy, New York 12180-3590, United States.
Vincent
V
Meunier
‡Center for Nanophase Materials Sciences and Computer Science and Mathematics Division, Oak Ridge National Laboratory, Bethel Valley Road, Oak Ridge, Tennessee 37831-6367, United States.
Bobby G
BG
Sumpter
†Department of Mechanical Engineering, Clemson University, Clemson, South Carolina 29634-0921, United States.
Rui
R
Qiao
electrical double layer; electrical energy storage; room-temperature ionic liquids; subnanometer pore; supercapacitor