A high mass loading electrode based on ultrathin Co₃S₄ nanosheets for high performance supercapacitor

Abstract

There is a growing need for the electrode with high mass loading of active materials, where both high energy and high power densities are required, in current and near-future applications of supercapacitor. Here, an ultrathin Co₃S₄ nanosheet decorated electrode (denoted as Co₃S₄/NF) with mass loading of 6 mg cm⁻² is successfully fabricated by using highly dispersive Co₃O₄ nanowires on Ni foam (NF) as template. The nanosheets contained lots of about 3∼5 nm micropores benefiting for the electrochemical reaction and assembled into a three-dimensional, honeycomb-like network with 0.5∼1 μm mesopore structure for promoting specific surface area of electrode. The improved electrochemical performance was achieved, including an excellent cycliability of 10,000 cycles at 10 A g⁻¹ and large specific capacitances of 2415 and 1152 F g⁻¹ at 1 and 20 A g⁻¹, respectively. Impressively, the asymmetric supercapacitor assembled with the activated carbon (AC) and Co₃S₄/NF electrode exhibits a high energy density of 79 Wh kg⁻¹ at a power density of 151 W kg⁻¹, a high power density of 3000 W kg⁻¹ at energy density of 30 Wh kg⁻¹ and 73 % retention of the initial capacitance after 10,000 charge-discharge cycles at 2 A g⁻¹. More importantly, the formation process of the ultrathin Co₃S₄ nanosheets upon reaction time is investigated, which is benefited from the gradual infiltration of sulfide ions and the template function of ultrafine Co₃O₄ nanowires in the anion-exchange reaction.