Nitrogen-rich doped carbon hollow nanocage structure cooperating with cobalt-nickel sulfide to improve the performance of supercapacitors

A novel nitrogen-rich doped carbon hollow nanocage (NC) supported binary metal sulfide nanoparticle (CoNixSy) composite CoNixSy/NC was successfully prepared by a simple pyrolysis-vulcanization two-step method. In this strategy, dimethylglyoxime nickel was used as the nickel source to increase the active site, and the core-shell structure of the precursor ZIF-8@Ni-ZIF-67 provided the possibility for the construction of hollow carbon nanocages. More importantly, this unique hollow structure loaded with binary metal sulfide nanoparticles made the CoNixSy/NC possess more active sites, high conductivity, and structural stability when used as an electrode material, thereby providing a higher specific capacity (629.2 F center dot g(-1) at 1 A center dot g(-1)) and excellent cycle stability (93.4% capacity retention after 1 000 cycles at 1 A center dot g(-1)). When further assembled into a symmetrical supercapacitor, a specific capacitance of 207.2 F center dot g(-1) can be provided at 1 A center dot g(-1), and the retention rate was 85.36% after 1 000 cycles of stabilization.