Novel in situ growing carbon nanocoils onto steel mesh as positive electrode and hexagonal-MoO3 micro-rod array onto carbon fabric as negative electrode for assembling dual-asymmetric supercapacitors with redox active gel eleectrolyte

Abstract Intrinsically functionalized carbon nanocoils (CNCs) are in-situ grown onto the microwire surface of stainless steel mesh (SS) in an alcohol flame. The CNCs are deposited without using any additional catalysts and the flame growth mechanism is proposed. Such a unique structure with functionalized CNCs directly growing onto SS micro-wires in the mesh current collector makes it an excellent binder-free CNC/SS electrode. It exhibits ultrahigh capacitance in a iron ion based redox active electrolyte, where an remarkable areal capacitance of 4160 mF/cm2 at 20 mA/cm2 can be achieved. Meanwhile, hexagonal MoO3 microrods are grown vertically onto carbon fibers and their electrochemical behaviors in normal H2SO4 electrolyte are investigated. Finally, novel dual-asymmetric supercapacitors (DASCs) with the configuration of CNC/H2SO4+PVA + Fe2+/3+//H2SO4+PVA/h-MoO3 are assembled. The device exhibits an excellent areal capacitance of 1502 mF/cm2 at 3 mA/cm2, and a remarkable ultrahigh energy density of 252.4 μW h/cm2 at the power energy of 1.6 mW/cm2 as well. The research is expected to promote the development of SCs with high energy density through the design and assembly of all their main components, including the direct growth of active materials onto current collectors and the appropriate utilizing the redox active gel electrolyte.