Blessing and Curse: How a Supercapacitor's Large Capacitance Causes its Slow Charging

Area of Science:

• Electrochemistry
• Materials Science
• Energy Storage

Background:

• Supercapacitor development is limited by discrepancies in charging time scales.
• Experimental and theoretical charging times differ significantly.

Purpose of the Study:

• To propose a novel electrode model explaining slow supercapacitor charging.
• To reconcile theoretical predictions with experimental observations.

Main Methods:

• Development of a parallel stacked electrode model.
• Analysis of charging dynamics at varying applied potentials.
• Comparison with equivalent circuit and experimental data.

Main Results:

• The model accurately describes low-potential charging with an equivalent circuit.
• At high potentials, two distinct relaxation times emerge: generalized RC and diffusion.
• These time scales converge for porous electrodes, matching experimental data.

Conclusions:

• The stacked electrode model provides insight into supercapacitor charging.
• It successfully explains the slow dynamics observed in porous electrodes.
• The model bridges the gap between theoretical and experimental charging time scales.