Electrospun Zn_{1- x}Mn_xFe₂O₄ nanofibers as anodes for lithium-ion batteries and the impact of mixed transition metallic oxides on battery performance

The structural and electrochemical properties of the mixed transition metallic oxides Zn_1-xMn_xFe₂O₄ nanofibers, which crystallize in a cubic spinel AFe₂O₄ structure, are investigated systematically with a gradual substitution of Zn by Mn. The crystal structural information studied by X-ray diffraction (XRD) depicts the formation of single phase spinel structure, while electron-dispersive X-ray spectroscopy (EDS) reveals the stoichiometric ratio between Zn and Mn. ZnFe₂O₄ exhibits a good capacity of ∼532 mAh g^-1 at 50th cycle through the interbeneficial conversion reaction and alloy-dealloy mechanism, with a first discharge working voltage of ∼0.83 V. Subsequently, the characteristic redox potential of each spinel is gradually reduced with the replacement of Mn. Furthermore, Zn _0.3Mn_0.7Fe₂O₄ demonstrates the highest capacity of ∼612 mA h g^-1 at 50th cycle among the solid solution series. Ex situ characterization by high-resolution transmission electron microscope (TEM) and electron energy loss spectroscopy (EELS) is conducted to study the participation of Mn in the battery performance. This report represents an example of how the electrochemical performance could be flexibly adjusted by tuning the ratio of transition metals within the spinel.