Preparation and electrochemical characteristics of porous carbon composites originating from hyper-crosslinked polymers

Abstract

A method of hyper-crosslinked polymers-derived carbon compounded with transition metal sulfides was employed in this study for suppressing the severe disadvantage of specific capacitance (SC) decay of transition metal sulfides due to volume variation and to enhancing supercapacitors' performance from the perspectives of power density and energy density, with the aim of addressing the challenge that carbon-based supercapacitors exhibit relatively lower energy density (ED). In this study, PNOC-800-3@NiS composites were well prepared based on the direct carbonization-chemical activation method with hyper-crosslinked polymer (PNO) as the precursor. Subsequently, PNOC-800-3@NiS composites were well prepared based on the hydrothermal approach with thiourea and PNOC-800-3 as the sulfur source and the substrate, separately. The effects exerted by different nickel-sulfur ratios and synthesis temperatures on the composites' electrochemical characteristics were studied. As revealed by the results, the surface area of PNOC-800-3@NiS-2-180 reached 1006.31 m2 g−1, and the pore diameter on average was 1.86 nm at the ratio of nickel to sulfur of 1:2 and the synthesis temperature of 180 °C. In the 6 M KOH electrolyte solution, composites exhibited the SC of 1051.2 F g−1 under a current density (CD) of 1 A g−1. With the rising CD in a range between 1 A g−1 and 10 A g−1, SC achieved a decay rate of 49.58 %. Under a power density (PD) of 700 W kg−1, a prominent ED was achieved by the assembled asymmetric supercapacitor, which was of 20.98 Wh kg−1. When 5000 cycles of discharging and charging was achieved, the composite PNOC-800-3@NiS-2-180 exhibited a capacitance retention rate of 72.63 %. Furthermore, as indicated by the result, the composite PNOC-800-3@NiS-2-180 exhibited prominent electrochemical characteristics, and can serve as one of the highly suitable electrode materials to be used in supercapacitors.