3D Reduced Graphene Oxide-Integrated N-Doped Carbon-Encapsulated CoS 2 /FeS 2 Heterostructure for Enhanced Sodium-Ion Storage

Rational engineering of electrode composition and architecture is an effective strategy to achieve high capacity and long cycling stability for sodium-ion batteries (SIBs). In this work, a CoS2/FeS2 heterostructure encapsulated within an N-doped carbon (NC) framework and further interconnected by a three-dimensional (3D) reduced graphene oxide (rGO) network (CoS2/FeS2@NC/rGO) was rationally designed and synthesized by an in situ carbonization–sulfidation process. The NC framework enhances the conductivity and structural stability, while the 3D rGO network provides continuous Na+ and electron transfer pathways and effectively inhibits the aggregation of particles during cycling. Moreover, the heterointerfaces between CoS2 and FeS2 promote Na+ diffusion and boost the redox activity, thereby facilitating reaction kinetics. Consequently, the CoS2/FeS2@NC/rGO anode exhibits an excellent rate performance of 518.1 mAh g–1 at 20 A g–1 and superior cycling performance (586.5 mAh g–1 at 2 A g–1 after 1400 cycles), demonstrating its potential in practical applications. Furthermore, ex situ XRD and Raman revealed the underlying Na+ storage mechanisms and structural stability of CoS2/FeS2@NC/rGO. This work provides valuable insights into the rational design of high-performance SIB anodes through heterostructure engineering and hierarchical structural optimization.