Co1−xFe2+xO4 (x = 0.1, 0.2) anode materials for rechargeable lithium-ion batteries

• Facile synthesis of cobalt-poor CoFe2O4 as an anode material.
• The threshold limit of lower cobalt stoichiometry in CoFe2O4 is identified.
• Unique stoichiometry and high conductivity of Co0.9Fe2.1O4 leads better electrode performance.
• The electrochemical performance of cobalt-poor CoFe2O4 is comparable to that of the pure phase.

A cobalt-poor or iron rich bicomponent mixture of Co0.9Fe2.1O4/Fe2O3 and Co0.8Fe2.2O4/Fe2O3 anode materials have been successfully prepared using simple, cost-effective, and scalable urea-assisted auto-combustion synthesis. The threshold limit of lower cobalt stoichiometry in CoFe2O4 that leads to impressive electrochemical performance was identified. The electrochemical performance shows that the Co0.9Fe2.1O4/Fe2O3 electrode exhibits high capacity and rate capability in comparison to a Co0.8Fe2.2O4/Fe2O3 electrode, and the obtained data is comparable with that reported for cobalt-rich CoFe2O4. The better rate performance of the Co0.9Fe2.1O4/Fe2O3 electrode is ascribed to its unique stoichiometry, which intimately prefers the combination of Fe2O3 with Co1−xFe2+xO4 and the high electrical conductivity. Further, the high reversible capacity in Co0.9Fe2.1O4/Fe2O3 and Co0.8Fe2.2O4/Fe2O3 electrodes is most likely attributed to the synergistic electrochemical activity of both the nanostructured materials (Co1−xFe2+xO4 and Fe2O3), reaching beyond the well-established mechanisms of charge storage in these two phases.

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