Lithium dual uptake anode materials: crystalline Fe3O4 nanoparticles supported over graphite for lithium-ion batteries

Highlights: •Magnetite-graphite hybrids were prepared by a simple and inexpensive synthesis. •Graphite's flake size defines the edge density and the amount of immobilized Fe₃O₄. •Fe₃O₄-G films' morphology controls the electrochemical properties of the anodes. •The deposition of Fe₃O₄ plays an important role in the electrochemical performance. •The anode with the smallest graphite particle size delivers a capacity of 845 mA h g⁻¹. -- Abstract: Graphite, the usual anode material for current technology of lithium ion batteries (LIB), has great advantages and its processing is widely known and industrially feasible. For improving the anode's capacity, recent research has focused in using nano-carbons as an overcoming strategy rather than including cheap, conversion-type oxide metals. Here, we present the application of in-situ synthesized hybrid LIB active anode materials composed of magnetite nanoparticles (Fe₃O₄ NPs) and graphite of different sizes. The results show that the graphite's flake size plays an important role in the Fe₃O₄ NPs deposition and loading, and therefore in the morphology of the resulting laminate film. The electrochemical performance (evaluated by cyclic voltammetry, galvanostatic charge/discharge cycles and impedance spectroscopy) is determined not only by the edge density of graphite flakes and Fe₃O₄ loading but also by the porosity of the anode films. The hybrid material electrode with smallest graphite particle size shows the highest reversible capacity of 845 mA h g⁻¹, good rate capability and great cycling performance. This remarkable improvement in graphite's capacity is reached by only adding 16 wt% of magnetite to the carbon material.