Self-assembled porous Fe3O4/C nanoclusters with superior rate capability for advanced lithium-ion batteries

Porous Fe3O4/C nanoclusters composed of nanopores with an average size of 7.1 and ~ 2 nm thick carbon layers inlaid homogenously with ~ 5.1 nm Fe3O4 nanocrystals are successfully prepared for the first time via a hydrothermal process using iron chloride hexahydrate, tri-sodium citrate, polyvinylpyrrolidone, glucose and sodium carbonate as starting materials. The obtained powders were systematically characterized by XRD, FESEM, TEM, BET and Raman techniques. It has been found that the self-aggregation of glucose molecules and Fe(OH)3 nanoparticles via the molecular chain entanglements between molecules during the condensation and carbonization of glucose should be responsible for the formation of the precursory agglomerates, which are then turned into the porous Fe3O4/C nanoclusters with complex microstructures. These porous Fe3O4/C nanoclusters used as an anode material for lithium-ion batteries exhibit a high reversible capacity of 997.6 mAh g−1 after 200 cycles at 1 A g−1, and a high-rate delivery of 807.6 mAh g−1 after 500 cycles at 4 A g−1. The superior performance of Fe3O4/C nanoclusters is mainly attributed to the local dynamic confinement of tiny Fe3O4 nanoparticles in the ultrathin porous carbon matrix.