Highly stable nickel-aluminum alloy current collectors and highly defective multi-walled carbon nanotubes active material for neutral aqueous-based electrochemical capacitors

Abstract

Neutral aqueous electrolytes are known to promote corrosion of carbon coated aluminum current collectors used in electrochemical capacitors, limiting their applications on energy storage devices. Alternatively to the standard electrode manufacturing recipe, we have grown multi-walled carbon nanotubes as the active material on modified aluminum foils to avoid the corrosion of the latter in neutral aqueous solutions. Therefore, the purpose of the present study is the fabrication of a binary alloy that is resistant to corrosion in neutral aqueous solutions. In this sense, we modified standard aluminum foil current collectors by coating them with a thin nickel layer, which was converted on nickel-aluminum alloy (NixAl, x = 1 & x = 3) during the first heating steps of nanotubes growth on the current collector. This novel aluminum modified current collector is electrically conductive and very resistant to corrosion, which allows applying aluminum-based current collectors on aqueous-based electrochemical capacitors devices. To better investigate the electrochemical performance of carbon-based electrodes in aqueous filled coin cell devices, we performed several electrochemical studies using cyclic voltammetry, galvanostatic charge/discharge, and electrochemical impedance spectroscopy. Our results show specific electrode capacitance is up to ∼60 F g−1. After 85,000 (re)charge/discharge cycles, the cell operating on 0–1.5 V voltage range, indicate very long lifespan with no significant loss of specific capacitance and energy density. These results are unexpected for aluminum current collectors on supercapacitor or batteries. On the Ragone plot, our aqueous-based electrochemical capacitor is on supercapacitors region with fairly high power and energy densities.