Improving Interfaces in All-Solid-State Supercapacitors Using Polymer-Added Activated Carbon Electrodes

Abstract

Solvent-free all-solid-state supercapacitors have recently received attention. Despite their highly specific capacitance, they suffer issues related to the solid–solid interface that degrade their performance during prolonged cycling. Here, we propose a novel strategy for improving the electrode–electrolyte interface by introducing a small amount of polymer into the activated carbon-based electrode. An electrode composition of 80AC:8SA:7AB:5[PEO0.95 (LiClO4)0.05]—where AC, SA, and AB stand for activated carbon, sodium alginate binder, and acetylene black, respectively—is optimized. A composite membrane—viz., PEO-LiClO4 reinforced with 38 wt% NASICON structured nano crystallites of Li1.3Al0.3Ti1.7(PO4)3—is used as a solid electrolyte. Incorporating a small amount of salt-in-polymer (95PEO-5 LiClO4) in the electrode matrix leads to a smooth interface formation, thereby improving the performance parameters of the all-solid-state supercapacitors (ASSCs). A typical supercapacitor with a polymer-incorporated electrode exhibits a specific capacitance of ~102 Fg−1 at a discharge current of 1.5 Ag−1 and an operating voltage of 2 V near room temperature. These ASSCs also exhibit relatively better galvanostatic charge–discharge cycling, coulombic efficiency, specific energy, and power in comparison to those based on conventional activated carbon.