Nitrogen-doped graphene/multiphase nickel sulfides obtained by NiC3N3S3 (metallopolymer) assisted synthesis for high-performance hybrid supercapacitors

Designing a hybrid architecture of electroactive species on the modified graphene sheets is one of the most promising tactics for high-performance supercapacitors. Herein, multiphase nickel sulfides nano-particles (Ni3S2-NiS, abbreviated as Ni-S-1) with abundant edge sites were synthesized by pyrolysis of three-dimensional porous Ni-C3N3S3 complexes, and then the N-doped graphene (NG)/Ni-S-1 hybrid was obtained by an introduction of graphene oxide. The NG/Ni-S-1 hybrid shows the electroactive species-on-sheet architectures and the heteroatom nitrogen doping into graphene. The unique structural composition of the NG/Ni-S-1 hybrid can accelerate the permeation and shorten the diffusion length of electrolyte ions, to perform favorable electrochemical charge storage kinetics. Remarkably, compared with Ni-S-1 electrode, the NG/Ni-S-1 hybrid electrode delivers an improved specific capacity of 732.1 C g(-1) at 1 A g(-1) and an excellent rate capability, which are attributed to more accessible surfaces and enhanced electron-transport capacity due to the integration of NG matrix. Furthermore, a hybrid supercapacitor assembled using the NG/Ni-S-1 hybrid as positive electrode and activated carbon (AC) as negative electrode demonstrates a high energy density of 40.2 Wh kg(-1), high power density of 7.4 kW kg(-1), and relatively good electrochemical stability. The facile strategy may offer a new opportunity for fabrication of transition metal sulfides-based hybrids for high-performance supercapacitors. (C) 2019 Elsevier Ltd. All rights reserved.