Co_(1-x)Fe_(2+x)O_4 (x = 0.1, 0.2) anode materials for rechargeable lithium-ion batteries

摘要

A cobalt-poor or iron rich bicomponent mixture of Co_(0.9)Fe_(2.1)O_4/Fe_2O_3 and Co_(0.8)Fe_(2.2)O_4/Fe_2O_3 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 CoFe_2O_4 that leads to impressive electrochemical performance was identified. The electrochemical performance shows that the Co_(0.9)Fe_(2.1)O_4/Fe_2O_3 electrode exhibits high capacity and rate capability in comparison to a Co_(0.8)Fe_(2.2)O_4/Fe_2O_3 electrode, and the obtained data is comparable with that reported for cobalt-rich CoFe_2O_4. The better rate performance of the Co_(0.9)Fe_(2.1)O_4/Fe_2O_3 electrode is ascribed to its unique stoichiometry, which intimately prefers the combination of Fe_2O_3 with Co_(1-x)Fe_(2+x)O_4 and the high electrical conductivity. Further, the high reversible capacity in Co_(0.9)Fe_(2.1)O_4/Fe_2O_3 and Co_(0.8)Fe_(2.2)O_4/Fe_2O_3 electrodes is most likely attributed to the synergistic electrochemical activity of both the nanostructured materials (Co_(1-x)Fe_(2+x)O_4 and Fe_2O_3), reaching beyond the well-established mechanisms of charge storage in these two phases.