High energy density hybrid supercapacitor based on cobalt-doped nickel sulfide flower-like hierarchitectures deposited with nitrogen-doped carbon dots
Zhenyuan Ji, Kai Liu, Wenyao Dai, Dongwei Ma, Hongyan Zhang, Xiaoping Shen, Guoxing Zhu, Shikui Wu
Abstract
The exploration of advanced electrode materials with outstanding electrochemical properties is of considerable importance for hybrid supercapacitors but challenging. In this paper, an effective two-step solvothermal route is demonstrated to synthesize nitrogen-doped carbon dots (NCDs) decorated cobalt-doped nickel sulfide (Co-NiS) flower-like hierarchitectures. Because of the modification with NCDs and doping by cobalt atoms, the resulting Co-NiS/NCDs hierarchitectures exhibit an ultrahigh specific capacity up to 1240 C g-1 (2480 F g-1) at 1 A g-1 and a remarkable rate capability of 790.8 C g-1 (1581.6 F g-1) even at 20 A g-1 when used as advanced electrodes for supercapacitors. More significantly, coupling with ap-phenylenediamine (PPD) modified reduced graphene oxide (rGO) anode, a hybrid supercapacitor device is successfully constructed, which possesses an impressive energy density of 71.6 W h kg-1 at 712.0 W kg-1 and a decent cyclic stability with 78.3% retention after 12 000 cycles at 5 A g-1. The dual improvement strategy may provide insight to rational engineering of novel electrode materials with multi-components for high-performance hybrid supercapacitors.