Effect of acid etching of stainless-steel foils in aqueous rechargeable lithium-ion batteries

The influence of hydrochloric acid etching on the surface properties and electrochemical performance of stainless-steel foils as current collectors for aqueous energy storage devices was investigated. Stainless-steel foils were etched at 80 °C for 10, 20, and 30 min, and the subsequent effects on surface roughness, wettability, and battery performance were investigated in detail. Etching for 10 min provided slight variations in the surface, while etching for 30 min encompassed serious corrosion with deep pits. The roughness shifted from 0.115 µm to 0.403 µm and enhanced the hydrophilicity. The measurements of the LiFePO₄ electrode demonstrated that 10-min etched foils delivered the highest capacity (~ 130 mAh g^-1) and stability compared to un-etched or further etched foils. The improved performance is due to moderate roughening, oxide layer removal, and higher contact area efficiency, and hence etching at 10 min is most appropriate for stainless-steel current collectors in aqueous batteries.