Multifunctional polymeric coating on stainless steel current collectors in aqueous energy storage devices

Herein, low cost stainless steel foils are employed as current collectors in aqueous Na-ion supercapacitors, while the foils are coated with following conducting polymers, namely, polyimide (PI), Schiff base polymer (SBP), polyanthraquinone sulfide (PAQS) and polyaniline (PANI). The foremost purpose of these polymeric coatings is the prevention of corrosion, and the resultant improvements in device performances. Notwithstanding, these polymeric coatings provide few additional benefits in device characteristics, and these are following: (i) enhancement of electrolyte stability window, (ii) contributing charge storage capacitance, (iii) conversion of 2D pristine substrate to 3D porous current collector. The four coating polymers are electrochemically characterized, and PI is selected for fabricating Na-ion supercapacitor cells. The PI-coating reduces the stainless steel's corrosion rate ∼ 68 times, expands the electrolyte stability window ∼ 1.2 times, and delivers ∼ 2 times higher capacitance with respect to pristine current collector, whereas no appreciable interfacial resistances are observed. The supercapacitor cell with PI-functionality demonstrates ∼ 6.6 times improved capacitance than that of pristine cell at 25 mA/g current density, while > 95 and ∼ 90 % Faradaic efficiencies are noted for former and latter, respectively. The distinct enhancement of cell performances clearly demonstrates the effectiveness of multifunctional polymeric coating on corrosion-prone metallic current collectors.