Facile Fabrication of Iron Cobalt Sulfide Nanoparticles within N‑Doped Graphene for High-Performance Supercapacitors

Supercapacitors (SCs) have been widely considered as they are competitive power sources for energy storage. Herein, we fabricated high-quality iron cobalt sulfide nanoparticles encapsulated on a N-doped graphene nanosheet (FeCoS2/NG) composite with a core–shell structure as an advanced positive electrode material for SCs by employing a simple, cost-effective, and scalable hydrothermal process. The thin NG shell-encapsulated FeCoS2 core interconnects with each other, which shortens the length of the ion diffusion path between the electrode and electrolyte, resulting in superior electrochemical performance. Remarkably, the FeCoS2/NG composite exhibited a maximum specific capacitance of 1420 F g–1 at a current density of 1 A g–1, an outstanding rate capability of 898 F g–1 at 30 A g–1, and exceptional cycle life with 85.1% retention of its initial capacitance after 10,000 consecutive cycles. Notably, the fabricated asymmetric SCs of FeCoS2/NG//NG achieved an excellent energy density of 79.3 W h kg–1 at a power density of 804 W kg–1 and outstanding cycle stability (capacitance retention of 90.2% after 10,000 consecutive cycles). The prominent property of the FeCoS2/NG electrode provides an effective route in the application of energy storage.