Graphite Layer Coated on Aluminium Foil as Anti-corrosion Current Collector for Neutral Aqueous Supercapacitors

Abstract

Neutral aqueous supercapacitors are of interest due to their many advantages such as low-cost, non-flammable, and high ionic conductivity. Interestingly, the current collector is a critical part of these devices since it can be corroded in aqueous electrolytes. The Al foil is a widely used current collector for commercial organic supercapacitors due to its low-cost. However, it is corroded in aqueous electrolytes. To address this issue, we develop the graphite coating layer on the Al current collector to suppress the corrosion of Al and the formation of an oxide-resistive film on Al in an aqueous electrolyte. The corrosion testing was confirmed by the electrochemical impedance spectroscopy (EIS). Furthermore, the electrochemical performance of the as-prepared electrodes with and without the graphite coated layer was studied by using cyclic voltammetry (CV) and galvanostatic charge/discharge (GCD). The as-prepared electrode with a graphite protective layer exhibits a higher specific capacitance as well as a higher rate capability. The capacitance fading upon increasing scan rate from 10 mV s-1 to 100 mV s-1 of graphite coated aluminium electrode was only 15%, while the capacitance of the unmodified electrode extremely faded up to 75%. The as-prepared electrode with a graphite protective layer can explicitly improve the cycling stability (retain 90 %) after 5,000 cycles at an applied current density of 1 A g-1, which is different from an unmodified electrode with rapid fading up to 55%. This finding may lead to practical neutral aqueous supercapacitors.