Porous olive-like carbon decorated Fe3O4 based additive-free electrodes for highly reversible lithium storage

Abstract

Porous nanostructured olive-like carbon decorated Fe₃O₄ (Fe₃O₄/C) was prepared via in situ carbothermal treatment of the porous olive-like composite of Fe₂O₃/C. The precursor porous olive-like Fe₂O₃/C nanoparticles were prepared through an ultrafast (75 min) one-pot solvothermal method. The porous olive-like Fe₃O₄/C and its precursor Fe₂O₃/C nanostructures were formed by aggregation of orderly aligned nanorods as building subunits. The successful conversion from Fe₂O₃/C to Fe₃O₄/C by in situ carbothermic partial reduction was evidenced by extensive characterization. Additionally, a novel centrifugation-assisted procedure (CAP) to prepare additive-free Fe₃O₄ based electrodes with active materials directly synthesized on the current collector was developed for the first time. The porous olive-like Fe₂O₃/C nanoparticles dispersed in ethanol were coated on Cu current collectors by centrifugation-assisted deposition (CAD) directly without any additives employed and subsequently heated to convert to a Fe₃O₄/C coated Cu disc which can be used as an electrode without any further process. In contrast, traditional electrode preparation involves multiple steps of slurry preparation, coating, drying in a vacuum oven and additives (e.g., PVDF binder, carbon black conductivity enhancer and NMP solvent) are employed in the process. The as-prepared additive-free porous Fe₃O₄/C based electrode exhibited superior electrochemical performances in lithium storage. Excellent cycling performance was achieved with a specific capacity at ∼800 mA h g⁻¹ for at least 235 cycles. Impressive rate performance was accomplished when tested under different currents: no significant capacity drop was observed when current was doubled and a specific capacity of 730 mA h g⁻¹ could be maintained at current of 1500 mA g⁻¹.