Charging Dynamics and Structure of Ionic Liquids in Nanoporous Supercapacitors*

Ionic liquid based nanoporous supercapacitors have recently attracted much attention as energy storage devices with remarkable cyclability and high power and energy densities. However, their use in high- frequency applications might be limited by a relatively slow charging process. We will first discuss the fluid structure within a slit-pore capacitor system [1] and report on the physics and optimization of charge/discharge cycles [2,3]. Step-voltage charging is slow because the coions become trapped in narrow pores of the supercapacitor electrodes. To avoid such trapping, a slow voltage-sweep charging is considered, which allows to accelerate the overall charging process substantially. We furthermore examine in detail the discharging process and will report on the effect of nonlinear charging functions.
[1] K. Breitsprecher et al., J. Chem. Phys. 147, 104708 (2017).
[2] K. Breitsprecher et al., ACS nano 12 (10), 9733 (2018) .
[3] K. Breitsprecher et al. Nature Comm., in press.