Nano-porous Al/Au skeleton to support MnO2 with enhanced performance and electrodeposition adhesion for flexible supercapacitors

Abstract

A nano-porous Al/Au skeleton is constructed to effectively improve the utilization rate of the active MnO₂ and the overall adhesion between the current collector and MnO₂ in an electrodeposition system. The Al/Au current collector is prepared by first forming a nano-porous structure on the surface of Al foil through etching modification, and subsequently coating an ultra-thin Au layer onto the Al foil. The active MnO₂ is electrodeposited on the Al/Au current collector to fabricate a novel Al/Au/MnO₂ electrode. The nano-porous skeleton supports MnO₂ to grow autonomously inside-out. The ultra-thin Au layer acts as a transition layer to improve the overall conductivity of the current collector (0.35 Ω m⁻¹) and to improve the adhesion with MnO₂ as well. Owing to the highly porous structure, the electrochemical properties of the electrode are greatly improved, as evidenced by a remarkable specific capacitance of 222.13 mF cm⁻² at 0.2 mA cm⁻² and excellent rate capability of 63% capacitance retention at 6.0 mA cm⁻². Furthermore, the assembled solid-state symmetric supercapacitor exhibits a high energy density of 0.68 mW h cm⁻³, excellent cyclic stability (86.3% capacitance retention after 2000 cycles), and prominent flexibility.