Plasma-assisted synthesis of ultra-fine NiCo2O4/NiCo-layered double hydroxides nanoparticles-decorated electrospun carbon nanofibers with enhanced electrochemical performance.

ABSTRACT

Nickel cobaltate/NiCo-layered double hydroxides (NiCo2O4/NiCo-LDH) as energy storage materials offer considerable potential for various applications. However, many of current methods for synthesizing NiCo2O4/NiCo-LDH suffer from long synthesis times, complex preparation process, and high temperatures and high pressures. In this study, we present a green, simple, and efficient approach known as assisted liquid-phase plasma electrolysis, which realizes the rapid fabrication of ultra-fine NiCo2O4/NiCo-LDH nanoparticle-decorated electrospun carbon nanofibers (NiCo2O4/NiCo-LDH/CNFs) composites. Ultra-fine NiCo2O4/NiCo-LDH nanoparticles (<70 nm) are uniformly deposited on the CNF surface. The CNFs are intertwined to form a highly conductive three-dimensional mesh structure, which synergizes the NiCo2O4/NiCo-LDH nanoparticles with a high specific capacitance in favor of ion/electron transport efficiency. In addition, the cooperative effect between the two phases of NiCo2O4 and NiCo-LDH further improves the electrochemical properties. The NiCo2O4/NiCo-LDH/CNFs composites exhibit a high specific capacitance of 1534.7 F/g at 1 A/g and a capacitance retention of 93.9 % after 5000 cycles. An assembled asymmetric supercapacitor using activated carbon and NiCo2O4/NiCo-LDH/CNFs composites achieves an energy density of 33.8 Wh/kg at a power density of 400 W/kg and a capacitance retention of 93.0 % after 5000 cycles. Notably, two series-connected NiCo2O4/NiCo-LDH/CNFs ASC supercapacitors can light up an LED bulb, which maintains a certain brightness even after 50 min. Hence, this work provides a new and efficient route for synthesizing carbon-based NiCo2O4/NiCo-LDH composites for use as advanced energy storage materials.