Molecular understanding of charge storage and charging dynamics in supercapacitors with MOF electrodes and ionic liquid electrolytes

TL;DR

This study uses molecular simulations to analyze charge storage and dynamics in MOF-based supercapacitors with ionic liquids, revealing structural factors that influence performance and potential for high energy and power densities.

Contribution

It introduces a nanoscale-to-macroscale modeling approach to understand and predict the performance of MOF supercapacitors, providing molecular insights for future design.

Findings

Capacitance depends on MOF structure and ion behavior under polarization

Charging dynamics can be characterized by a transmission line model

MOF supercapacitors show potential for high volumetric energy and power densities

Abstract

We present a computational microscopy analysis (targeted molecular dynamics simulations) of the structure and performance of conductive metal organic framework (MOF) electrodes in supercapacitors with room temperature ionic liquids. The molecular modeling predicts the characteristic shapes of the potential dependence of electrode capacitance, relying on the structure of MOF electrodes and particularly how ions transport and reside in MOFs under polarization. Transmission line model was adopted to characterize the charging dynamics process and build up a bridge to evaluate the capacitive performance of practical supercapacitor devices at macroscale from the simulation-obtained data at nanoscale. Such nanoscale-to-macroscale analysis demonstrates the potential of MOF supercapacitors for achieving unprecedentedly high volumetric energy and power densities. The investigation gives molecular insights into the preferred structures of MOF for achieving these results, which could provide a blueprint for future experimental characterization of these new systems.