An embedded heterostructure Fe2O3@α-FeOOH/RGO with optimized SEI film and fast Li-ion diffusion

As an indispensable part of lithium-ion batteries (LIBs), the quality of solid-electrolyte interphase (SEI) influences directly the electrochemical performance. α-FeOOH with superior theoretical capacities, low cost, and environmental friendliness has been regarded as a promising anode of LIBs. In this work, we found that the hydroxyl groups on the surface of α-FeOOH bond with organic electrolytes that forming an inferior SEI layer contained excessive ROCO₂Li, finally causing a poor Li⁺ transport. Thus, we construct a novel heterostructure of spindle-like α-FeOOH nanorods embedded in mulberry-like Fe₂O₃ sphere on reduced graphene oxide sheets (F@F/C) based on the dissolution-recrystallization mechanism to optimize the composition of SEI layers. The content of ROCO₂Li is decreased as expected in the SEI of F@F/C electrode, which diminish the ionic transfer impedance in the interface and provide more alternative diffusion pathways. As expected, the heterostructural hybrid achieves an excellent electrode performance with a reversible capacity about 1800 mAh g⁻¹ at 0.2 A g⁻¹ after 300 cycles. Even cycled at a high current density of 1 A g⁻¹, the hybrid also remains 1050 mAh g⁻¹ after 600 cycles with a capacity decay rate of only 0.005% per cycle.