Symmetrizing cathode-anode response to speed up charging of nanoporous supercapacitors

TL;DR

This study uses molecular dynamics simulations to analyze asymmetric charging behaviors in nanoporous supercapacitors, revealing how symmetrizing ion responses can enhance power density.

Contribution

It uncovers the asymmetric features of charging dynamics in nanoporous supercapacitors and proposes symmetrizing ion responses to improve performance.

Findings

Charging dynamics can be fast despite slow ion diffusion.

Multi-pore electrodes exhibit overcharging and co-ion desorption.

Symmetrizing ion response boosts power density.

Abstract

Asymmetric behaviors of capacitance and charging dynamics in the cathode and anode are general for nanoporous supercapacitors. Understanding this behavior is essential for the optimal design of supercapacitors. Herein, we perform constant-potential molecular dynamics simulations to reveal asymmetric features of porous supercapacitors and their effects on capacitance and charging dynamics. Our simulations show that, counterintuitively, charging dynamics can be fast in pores providing slow ion diffusion and vice versa. Unlike electrodes with single-size pores, multi-pore electrodes show overcharging and accelerated co-ion desorption, which can be attributed to the subtle interplay between the dynamics and charging mechanisms. We find that capacitance and charging dynamics correlate with how the ions respond to an applied cell voltage in the cathode and anode. We demonstrate that symmetrizing this response can help boost power density, which may find practical applications in supercapacitor optimization.