Dragon fruit-like diphase heterostructure C@Fe1−xS/FeS2 composite with high-rate capability and long-cycle life for sodium-ion storage

The high theoretical capacity of iron-based sulfide makes it a promising cathode material for sodium-ion batteries. However, the extensive application of Na+ is limited by numerous issues, such as poor electrical conductivity stemming from slow ionic conduction kinetics. In this study, a diphase heterostructure nanocomposite (C@Fe1−xS/FeS2) was designed by combining heterostructure engineering with carbonaceous materials. According to X-ray diffraction (XRD) analyses, the as-prepared sample exhibited a diphase structure. Microscopic examinations revealed a dragon fruit-like morphology formed by carbon and Fe1−xS/FeS2, where carbon is wrapped by Fe1−xS/FeS2. The C@Fe1−xS/FeS2 composite exhibited remarkable electrochemical performance as cathode materials for sodium-ion batteries. Notably, the discharge capacity maintained a value of 370.4 mA h g−1 after 500 cycles at a current density of 500 mA g−1 within the voltage range of 0.8–3.0 V. Remarkably, the discharge capacity remained at 253.6 mA h g−1 after 2000 cycles, even when cycled at a current density of 1000 mA g−1. Additionally, the diphase heterostructure C@Fe1−xS/FeS2 improves the conductivity of the material and buffers capacity loss. These advantageous features are attributed to the dragon fruit-like structure constructed from carbon and Fe1−xS/FeS2.