The Modification of the Pore Characteristics of Activated Carbon, for Use in Electrical Double Layer Capacitors, through Plasma Processing

Wednesday, 31 May 2017: 17:40
Churchill C1 (Hilton New Orleans Riverside)
M. L. Muriel, R. Narayanan, and P. R. Bandaru (University of California, San Diego)
An important issue related to energy harness concerns obtaining high capacitance and related energy density in electrochemical capacitors (ECs), which have been mostly noted for high power density. In this paper, we address the possibility of obtaining enhanced capacitance in activated carbon based electrodes in ECs through the plasma processing, which has been hypothesized to introduce additional charge states in the electrode.

It was determined, based on extensive electrochemical experimentation and correlation of all the standard testing procedures (including constant current charge/discharge, cyclic voltammetry, and electrochemical impedance spectroscopy) that there is an optimal plasma processing at which both an increased capacitance as well as reduced resistance were observed, promising an enhancement in both energy and power density. For instance, while an increase of up to 35% of the gravimetric capacitance, along with ~ 20% decrease in resistance, was obtained through optimal plasma processing, increased plasma exposure yielded a drastic reduction (/increase) in the capacitance (/resistance).

It was also found that the capacitance and resistance modulation was a sensitive function of sample processing as well as electrochemical testing procedure. Considering the complexity of modeling realistic porous matrices, a metric to parameterize the reach of an electrolyte into the matrix has been posited.

Considering the difficulty of representing actual porous matrices, and as an alternative to relatively simplified lumped parameter models, we propose, for the first time in this paper, a new parameter indicating the reach of the electrolyte into the porous electrode, and which considers the extent to which a given testing procedure may be considered complete.  We expect that our method of analysis and experimental demonstrations will have a major impact, through providing insight into understanding how the energy and power capacity of electrochemical capacitors may be enhanced.