Carbon-covered Fe3O4 hollow cubic hierarchical porous composite as the anode material for lithium-ion batteries

In this work, Prussian blue nanocrystals, a kind of cubic metal-organic frameworks, was firstly covered by a uniform layer of resorcinol-formaldehyde (RF) resin, and then followed with heat treatment at different pyrolysis temperatures. The effects of pyrolysis temperature on the morphologies, phase, pore size, and electrochemical performance of the pyrolysis products were studied in this work. The composite generated at 600 ∘C, FexC600, was a hollow cubic composite of Fe3O4 covered by a thin RF-derived carbon layer. The carbon layer on FexC600 was a robust and conductive protective layer, which can accommodate Fe3O4 NPs and withstand the huge volume change of Fe3O4 during the process of discharge and charge. When used as anodes for lithium-ion batteries, FexC600 showed excellent electrochemical performance. It delivered a discharge capacity of 1126 mAh g−1 with a coulombic efficiency of 98.8% at the current density of 100 mA g−1 after 100 times discharge/charge cycling. It even delivered a capacity of 492 mAh g−1 at the current density of 500 mA g−1. This cubic hollow composite would be a promising alternative anode material for lithium-ion batteries.