Structural Stability Boosted in 3D Carbon-Free Iron Selenide through Engineering Heterointerfaces with Se-P Bonds for Appealing Na+-Storage

Iron selenides have emerged as appealing anodes for Na+-storage due to their natural abundance, good redox reversibility, and high theoretical capacity. Nevertheless, exploring a carbon-free iron selenide anode with long-term stability and high-rate capability remains an intractable challenge. Herein, a 3D carbon-free iron selenide electrode is designed by heterointerface with Se-P bond engineering strategy to realize outstanding Na+-storage performance. Theoretical calculations on the stress deformation confirm the construction of Fe7Se8/Fe-3(PO4)(2) not only enables excellent resistance-to-deformation ability but also exhibits strong mechanically stable against sodiation-desodiation. Such fascinating properties combined with the accelerated Na+ diffusion kinetics and enhanced electronic conductivity endowed by the 3D interconnected framework contribute to impressive cycling stability and superb rate performance for Na+-storage. Consequently, the designed 3D Fe7Se8/Fe-3(PO4)(2) composite with a high tap density of 0.91 cm(3) g(-1) displays a stable specific capacity of 277.1 mAh cm(-3) at 30 A g(-1), and outstanding long-term cycle stability of up to 1500 cycles at 5 A g(-1) without obvious capacity decay. The proposed engineering strategy and results provide new insight to design carbon-free advanced electrodes for future practical applications.