Graphene boosted pseudocapacitive lithium storage: A case of G-Fe₂O₃

High standards and urgent demands have been proposed for electrode materials because of the increasing market of rapid electrical power supply systems. Pseudocapacitance could provide an effective way for the development of electrode materials with both high energy and power densities. 3D graphene/α-Fe₂O₃ nanocrystal composites have been inspired by the combination of facet engineering and composite construction. The materials are evaluated as anode materials for secondary lithium ion batteries. Compared with the pristine α-Fe₂O₃ nanocrystal with oriented facet, the composites render evidently enhanced rate capability and long life span. Reversible capacities of 674 mA h g⁻¹ (420^th cycle) and 336 mA h g⁻¹ (750^th cycle) can be retained at relatively high rates of 1.0 A g⁻¹, and 5.0 A g⁻¹, respectively. Further investigations reveal that this outstanding performance is attributed to the enhanced pseudocapacitive contribution. The highly interconnected graphene matrix in the 3D composites provide fast electron transport pathways, and facilitate rapid ion diffusion, which eventually promote the pseudocapacitive lithium storage. The composite proves to be a promising candidate as a high-rate electrode material for lithium ion batteries.