Rice crust-like Fe3O4@C/rGO with improved extrinsic pseudocapacitance for high-rate and long-life Li-ion anodes

Transition oxides are a kind of promising anode materials for lithium-ion batteries due to their high capacity and low cost. However, it is a great challenge to realize high power density and long cycle life. Size control and surface coating are effective ways to increase reaction sites and improve electrical conductivity. In this work, rice crust-like structure of thin carbon layer coated Fe3O4 nanoparticles (~15 nm) uniformly covering rGO sheets (Fe3O4@C/rGO) is achieved. This composite delivers a high capacity of 594 mAh g−1 even after 1000 cycles at a high current rate of 5.0 A g−1, which can be attributed to the high surface pseudocapacitance dominated storage mechanism. Further analysis reveals that the high extrinsic pseudocapacitance is closed to the nanosized structure and carbon coating, because large surface area and good electrical conductivity are essential for the improvement of extrinsic pseudocapacitance. This work offers a new perspective for future structure design for high-rate and long-life anode materials of lithium-ion batteries.