Ytterbium-Induced In Situ Formation of Fe2O3/YbFeO3 Heterostructure: A Highly Stable Capacitive Anode Material for Lithium-Ion Batteries.

Iron oxide is a promising candidate for a lithium-ion battery anode material due to its high theoretical capacity, yet it suffers from poor conductivity and severe volume expansion. This work utilizes rare-earth ytterbium (Yb) modification to engineer the crystal structure of iron oxide via in situ construction of a Fe2O3/YbFeO3 heterostructure. Ytterbium was selected for its unique electronic structure and larger ionic radius, enabling adjustment of the local electronic environment and enhancing structural tolerance. Using FeCl3 and YbCl3 as precursors, a Fe-Yb composite with a molar ratio of 20:1 was synthesized via hydrothermal synthesis, followed by calcination at 700, 800, and 900 °C. The calcination temperature critically influenced electrochemical performance, with the 800 °C-treated sample (FeYb-800) exhibiting optimal characteristics: it retained a high reversible capacity of 700 mAh g-1 after 100 cycles and maintained a stable capacity of ~600 mAh g-1 after 500 cycles at 0.5 A g-1. Structural analysis indicates that ytterbium incorporation promotes the formation of a porous Fe2O3/YbFeO3 heterostructure. This architecture not only provides abundant active sites but also mitigates volume changes during cycling, effectively suppressing electrode degradation. This study successfully validates a viable strategy for fabricating high-performance anode materials with promising potential for high-energy-density lithium-ion batteries via rare-earth ytterbium modification.