Capacitance-Power-Hysteresis Trilemma in Nanoporous Supercapacitors

TL;DR

This paper presents an analytical and simulation-based study revealing that nanoporous supercapacitors can achieve high capacitance with larger pores by tuning ion affinity, potentially overcoming the traditional trade-off between capacitance and power, while also addressing hysteresis effects.

Contribution

It introduces a new understanding of how ion affinity influences capacitance and charging dynamics, proposing strategies to avoid the capacitance-power-hysteresis trade-off in supercapacitors.

Findings

High capacitance achievable in larger pores with ionophobic surfaces.

Charging can be hysteretic with energy loss at intermediate ion affinities.

Parameter regimes identified to overcome the capacitance-power-hysteresis trade-off.

Abstract

Nanoporous supercapacitors are an important player in the field of energy storage that fill the gap between dielectric capacitors and batteries. The key challenge in the development of supercapacitors is the perceived trade-off between capacitance and power delivery. Current efforts to boost the capacitance of nanoporous supercapacitors focus on reducing the pore size so that they can only accommodate a single layer of ions. However, this tight packing compromises the charging dynamics and hence power density. We show via an analytical theory and Monte Carlo simulations that charging is sensitively dependent on the affinity of ions to the pores, and that high capacitances can be obtained for ionophobic pores of widths significantly larger than the ion diameter. Our theory also predicts that charging can be hysteretic with a significant energy loss per cycle for intermediate ionophilicities. We use these observations to explore the parameter regimes in which a capacitance-power-hysteresis trilemma may be avoided.