Hybrid supercapacitors: A simple electrochemical approach to determine optimum potential window and charge balance

Abstract

In this work, we introduced novel, and simple electrochemical principles to guide the choice of the safe and valid operating potential window profile for carbon-based hybrid supercapacitor. The start vertex potential of the cyclic voltammograms (CVs) is set as the potential of zero charge (PZC). However, the final potential limit is chosen after elucidation of the storage mechanism using the CVs measured at various potential scan rates across the overall examined potential window. In addition, the mass and charge balance of the fabricated hybrid electrodes are rationally designed after evaluation of the potential window of the two separate electrodes. Using those strategies, a record performance merits are achieved of a hybrid device made up of carbon derived from biomass and carbon derived EDTA salt. The assembled device exhibits a specific capacitance 265 F/g at 5 mV/s and 221 F/g at 1 A/g with a high capability rate. Moreover, the device shows exceptional stability over 10,000 cycles with 100% capacitive retention and near 100% columbic efficiency. Most importantly, attaining a battery-like energy level of 99.2 W h/kg is a proof of concept that validates the proposed electrochemical fundamental methods for monitoring the mass ratio balancing of the hybrid cell electrodes.