Fabricating advanced asymmetric supercapacitors by flame growing carbon nanofibers on surface engineered stainless steel electrode and modulating the redox active electrolyte

Abstract

A straightforward approach for preparing a hierarchical carbon nanofiber (CNF) electrode through surface-engineering of a stainless steel microwire mesh (SS) current collector is developed. Surface-engineering is achieved via controlled chemical etching SS and subsequent flame depsotion of a CNF coating. In contrast to pristine SS, the surface-engineered SS do not only comprise a unique surface texture but also a higher catalytic activity facilitating the direct growth of CNFs in an ethanol flame. Therefore, the as-fabricated electrode exhibits a high specific capacitance of 2988 F/g at 25 mA/cm 2 in a redox active electrolyte containing Fe 2+/3+ optimized for this electrode/electrolyte system. To maximize their capacitive performance, supercapacitors in a newly designed dual-asymmetric electrode/electrolyte (DASCs) configuration are assembled. Both the CNF positive electrode and the alpha‑molybdenum oxide (MoO 3 ) nanobelt negative electrode are capable to operate in their most suitable electrolyte. Consequently, the DASCs deliver an ultrahigh energy density of 96 Wh/kg at 114 W/Kg and a remarkable capacitance retention. Our results demonstrate the effectiveness of this surface engineering approach for fabricating electrodes, the redox activity modulation of the electrolyte, and the newly designed configuration of the capacitors, on enhancing their performance. • A facile 2-step method for flame catalytic deposition of CNFs on stainless steel mesh was developed. • Surface-engineering provided the resurfaced catalytically active sites for CNF deposition. • Surface-engineering of the mesh provided CNF electrodes with enhanced charge transfer ability. • Supercapacitors with new configuration of dual-asymmetric electrode/electrolyte were assembled. • The flexible solid state device exhibited remarkable energy density of 96 Wh/kg at 114 W/kg.