Effects of Pore Structure and Carbon Loading on Solid Capacitive Devices at Low Temperatures

Abstract

The effects of electrode material loading and operating temperature on solid-state electrochemical double layer capacitors (EDLCs) with Na2SO4-polyacrylamide-DMSO electrolyte were studied. Two types of solid EDLC cells, using carbon nanotube (CNT) or activated carbon (AC), with very different surface areas and pore structures were compared to reveal the limitations in designing solid capacitive devices. Based on the gravimetric capacitance values, the utilizable portion of the electrode for EDLC can be estimated. Although increasing carbon loading leads to higher capacitance, there are two possible adverse effects especially at low temperatures. A high loading and thick electrode may reduce the penetration of viscous polymer electrolyte precursor solutions and may increase diffusion limitation leading to lower material utilization. These phenomena are more aggravated at faster rates and on micropore-rich materials. The results from this work can be used to quantify the effective utilization of the materials at different temperatures and the insights can be added to the guiding principles for designing and developing solid EDLCs.