Interconnected graphene nanosheets with confined FeS₂/FeS binary nanoparticles as anode material of sodium-ion batteries

Metal sulfides/graphene hybrid nanomaterials have drawn tremendous research interest for developing high-performance electrodes of sodium-ion batteries. Nevertheless, the rate performance still should be addressed due to the propensity to π-π stacking between graphene nanosheets. In this work, we develop a hybridized 3D network material configuration which is constructed by interconnected monodispersed graphene nanosheets (MGNs) with confined FeS₂/FeS hetero-nanoparticles (NPs) as the main active matter through a facile cold quenching-gas phase sulfidation technology. Benefiting from the distinctly wrinkled surface feature, the π-π restack between the graphene nanosheets is prevented, and meanwhile these MGN building blocks connect together by overlapping the edge regions to form a penetrative electrode framework with rich multiscale pores. Thus, the FeS₂/FeS NPs@MGN hybrid electrode exhibits greatly enhanced Na-ion transport kinetics and excellent rate capability. Typically, under an ultrahigh current density of 20 A g⁻¹, the reversible capacity of 251 mAh g⁻¹ with high capacity retention of 52.7% still can be achieved. In addition, it is found the FeS₂/FeS NPs are firmly confined in the wrinkles of the graphene nanosheets even after the repeated sodiation/disodiation processes, which contributes to the favorable structure stability and nearly decay-free cycling performance. A high discharge capacity of 513 mAh g⁻¹ at 0.1 A g⁻¹ is well maintained after 100 discharge/charge cycles due to the robust 3D graphene framework and the effective prevention of the active NPs from agglomeration and pulvaration by means of the confinement of graphene nanosheets. Furthermore, the superior confine effect on the suppression of polysulfide shuttling and the loss of active materials is also demonstrated.