Nickel cobaltite nanograss grown around porous carbon nanotube-wrapped stainless steel wire mesh as a flexible electrode for high-performance supercapacitor application

Abstract

Nickel cobaltite nanograss with bimodal pore size distribution (small and large mesopores) is grown on various electrode substrates by one-pot hydrothermal synthesis. The small pores (<5nm) in the nanograss of individual nanorods contribute to large surface area, while the large pore channels (>20nm) between nanorods offer fast transport paths for electrolyte. Carbon nanotubes (CNTs) with high electrical conductivity wrap around stainless steel (SS) wire mesh by electrophoresis as an electrode scaffold for supporting the nickel cobaltite nanograss. This unique electrode configuration turns out to have great benefits for the development of supercapacitors. The specific capacitance of nickel cobaltite grown around CNT-wrapped SS wire mesh reaches 1223 and 1070Fg−1 at current densities of 1 and 50Ag−1, respectively. CNT-wrapped SS wire mesh affords porous and conductive networks underneath the nanograss for rapid transport of electron and electrolyte. Flexible CNTs connect the nanorods to mitigate the contact resistance and the volume expansion during cycling test. Thus, this tailored electrode can significantly reduce the ohmic resistance, charge-transfer resistance, and diffusive impedance, leading to high specific capacitance, prominent rate performance, and good cycle-life stability.