On the cycling stability of biomass-derived carbons as electrodes in supercapacitors

Abstract

The present work provides new insight into the long-term cycling stability of biomass-derived activated carbons as electrodes in symmetric supercapacitors on the basis of ex-situ and post-mortem spectroscopic and microscopic analyses. The physicochemical characterization of activated carbons is carried out by DTA/TG, XPS spectroscopy, SEM, AFM and BET analyses. The surface functional groups and pore size distribution are determined by Böhm titration method and Barett-Joyner-Halenda analysis, respectively. The supercapacitor performance of the composite electrodes is tested by charge/discharge galvanostatic experiments. To go inside into surface and bulk electrode changes during electrode cycling, the post-mortem XPS, SEM/EDS and AFM experiments are undertaken. It is found that activated carbon having higher content of acidic groups and narrow pore size distribution displays an impressive cycling stability in alkaline electrolyte solution. The observed changes in electrode morphology during cycling are discussed on the basis of electrode-electrolyte interaction.