FeCo₂S₄@Ni@graphene Nanocomposites with Rich Defects Induced by Heterointerface Engineering for High-Performance Supercapacitors

Rational designing advanced materials with multicomponents and multiscale nanostructures is an important pathway to promote the rapid development and practical application of high-performance supercapacitors. Herein, FeCo2S4@Ni@graphene nanocomposites are prepared through electroless deposition—hydrothermal two-step method. In this hybrid structure, the metal nickel as a conductive bridge significantly enhances the charge transport and the structural stability between FeCo2S4 and graphene by encouraging the heterogeneous nucleation of FeCo2S4 on the active Ni@graphene. More importantly, the rich defects are induced into FeCo2S4@Ni@graphene by the interface engineering due to the lattice mismatch at the interface between Ni and FeCo2S4 and partial substitution of Ni for Co or Fe. These defects can provide additional faradic redox reactions and abundant active sites. Benefiting from the synergies of above advantages, the optimized FeCo2S4@Ni@graphene shows a specific capacity of 390.0 mAh g–1 at 1 A g–1. Additionally, the asymmetric supercapacitor based on FeCo2S4@Ni@graphene delivers a high energy density of 65.8 Wh kg–1 at 849 W kg–1, as well as capacitance retention of 89.2% after 6000 cycles at 20 A g–1. This work proposes an effective strategy, which is to regulate the defects in transition-metal compounds through heterointerface engineering to prepare advanced energy-storage materials.