Potential Substrates for Low-Cost Flexible Supercapacitors

Over the past several years, there has been a growing interest in the application of supercapacitors as replacements for conventional batteries, which are significant contributors of heavy metals into the environment. Flexible supercapacitors, unlike the traditional rigid supercapacitor, can be constructed with more accessible and cheaper flexible substrates. I constructed carbon nanotube (CNT) test samples using three low-cost substrates—polydemethylsiloxane (PDMS), polycarbonate (PC), and Scotch-brand matte adhesive tape—and looked at whether or not stress on the horizontally-aligned CNT affected the supercapacitor’s performance with respect to capacitance, resistance, and cost. Using a Teflon tube to achieve horizontally-aligned carbon nanotubes (HA-CNT) prior to delamination in deionized water, the CNT were subjected to bending tests of varying degrees on all three substrates as well as cycling tests to measure specific capacitance in both a concave and convex orientation. There was no significant increase in resistance in any of the substrates to indicate a damaged CNT forest. Specific capacitances for the densified CNT samples were at least twice that of an undensified CNT sample. As for which material is best, because the PDMS, PC, and tape samples all performed well in the resistance tests, the choice depends on the application and which characteristics are required of the substrate. With its already remarkably high power density and long lifetime, flexible supercapacitor can now be manufactured at a lower cost and applied to a wider range of technologies than traditional rigid supercapacitors, providing the necessary foothold for future supercapacitors in the competitive energy storage market.