Capacitive Performance and Tortuosity of Activated Carbon Electrodes with Macroscopic Pores

Abstract

The rate of ionic conduction through the electrolyte of porous electrodes is determined in part by the tortuosity, a factor describing the effective length an ion must travel through the microstructure's pores. To facilitate ionic conduction and adsorption into the electric double-layers of capacitive electrodes, we show that macroscopic pores can be added to reduce the effective tortuosity by providing more direct paths to capacitive interfaces. We show experimental and simulated results of fabricating and testing electrodes that are machined to include macro-pores aligned normal to current collectors. Through the reduction of tortuosity, these "bi-tortuous" electrodes surpass unpatterned electrodes in effective ionic conductivity and capacitance. The degree of improvement is dependent on the electrodes' thickness and charging rate.