Facile Fabrication\nof Iron Cobalt Sulfide Nanoparticles\nwithin N‑Doped Graphene for High-Performance Supercapacitors

Abstract

Supercapacitors (SCs) have been widely considered as\nthey are competitive\npower sources for energy storage. Herein, we fabricated high-quality\niron cobalt sulfide nanoparticles encapsulated on a N-doped graphene\nnanosheet (FeCoS₂/NG) composite with a core–shell\nstructure as an advanced positive electrode material for SCs by employing\na simple, cost-effective, and scalable hydrothermal process. The thin\nNG shell-encapsulated FeCoS₂ core interconnects with each\nother, which shortens the length of the ion diffusion path between\nthe electrode and electrolyte, resulting in superior electrochemical\nperformance. Remarkably, the FeCoS₂/NG composite exhibited\na maximum specific capacitance of 1420 F g^–1 at\na current density of 1 A g^–1, an outstanding rate\ncapability of 898 F g^–1 at 30 A g^–1, and exceptional cycle life with 85.1% retention of its initial\ncapacitance after 10,000 consecutive cycles. Notably, the fabricated\nasymmetric SCs of FeCoS₂/NG//NG achieved an excellent energy\ndensity of 79.3 W h kg^–1 at a power density of 804\nW kg^–1 and outstanding cycle stability (capacitance\nretention of 90.2% after 10,000 consecutive cycles). The prominent\nproperty of the FeCoS₂/NG electrode provides an effective\nroute in the application of energy storage.