Interfacial Electric-Field Nanoarchitectonics of a 3D FeS₂/SnS₂/rGO Heterostructure for Fast Sodium Storage

Developing high-performance FeS₂-based anodes for sodium-ion batteries is impeded by sluggish kinetics, poor conductivity, and severe volume variation. Herein, we report a rationally designed FeS₂/SnS₂/rGO composite featuring a three-dimensional hierarchical heterostructure. In this architecture, SnS₂ nanosheets are uniformly anchored on reduced graphene oxide framework, while FeS₂ nanoparticles are dispersed throughout the scaffold, forming interconnected electron pathways and structural robustness. More importantly, the abundant FeS₂-SnS₂ heterointerfaces induce built-in electric fields that regulate charge redistribution and accelerate interfacial reaction kinetics, thereby promoting surface-dominated pseudocapacitive behavior and rapid Na⁺ diffusion. As a result, the FeS₂/SnS₂/rGO electrode delivers a high reversible capacity of 618 mAh g^-1 at 0.1 A g^-1 and retains 500 mAh g^-1 at 5 A g^-1, together with outstanding cycling stability (536 mAh g^-1 after 400 cycles at 2 A g^-1 with 99.5% retention). Furthermore, full cells paired with NaNi_1/3Fe_1/3Mn_1/3O₂ exhibit good rate capability and long-term stability. This work demonstrates that heterointerface-induced electric-field regulation is an effective strategy for accelerating reaction kinetics in conversion-type anodes.