Nanocrystalline Heterostructure with Low Voltage Hysteresis for Ultrahigh-Power Sodium-Ion Capacitors

Heterostructures have garnered widespread attention for their ability to facilitate additional charge transfer, enhancing reaction kinetics and providing unprecedented effects at the interface. However, the majority of synthesized heterostructures exhibit non-uniform distribution and a scarcity of heterointerfaces, imposing significant constraints on their efficacy in sodium storage. In this study, a novel conceptualization of doping-reconstructed nanocrystalline heterostructures is introduced for the first time. Building upon this innovative concept, heterostructures characterized by uniform distribution and an abundance of heterointerfaces were successfully synthesized by reconstructing different Fe-doped Cu-based precursor into Cu2S/Cu5FeS4. Benefit by higher conductivity, a smaller sodium ion diffusion barrier, and lower voltage hysteresis, MOF-derived heterostructures maintained a capacity of 274.2 mAh g−1 after 2800 cycles at 30 A g−1. Furthermore, mineral-derived nanocrystalline heterostructures Cu2S/Cu5FeS4 (CFCS) with high tap density (3.71 g cm−3), prepared from Fe-containing copper smelting slag, exhibited a volumetric capacity 8.3 times higher than that of MOF-derived nanocrystalline heterostructures at 5.0 A g−1. The sodium-ion capacitor assembled with CFCS and activated carbon provided a high energy density of 60.1 Wh kg−1 at a high power density of 43.2 kW kg−1. This work presents a method for the controllable synthesis of uniform heterostructure with rich heterointerfaces, offering applicability.