Synthesis and lithium electrode application of ZnO−ZnFe2O4 nanocomposites and porously assembled ZnFe2O4 nanoparticles

The mixed metal oxide nanocomposites composed of spinel ZnFe2O4 and wurzite ZnO phases are prepared by the heat-treatment for Zn,Fe-layered double hydroxide (Zn,Fe-LDH) at elevated temperatures. The following selective etching of ZnO domains from the nanocomposites yields porously assembled ZnFe2O4 nanocrystals. The structural transformation from the brucite LDH structure to the spinel and/or wurzite structures was confirmed by X-ray diffraction and X-ray absorption spectroscopy. According to chemical analysis, electron microscopy, and N2 adsorption−desorption isotherm measurements, not only the chemical composition of the nanocomposites but also the particle size and surface area of the etched ZnFe2O4 nanoparticles can be controlled by changing the Fe/Zn ratio in the precursor metal hydroxide. The calcined nanocomposites show promising functionality as negative electrode materials for lithium ion batteries, which is superior to that of uncomposited ZnFe2O4 or ZnO phase. The degrading of the electrode performance of the nanocomposites after the selective etching of ZnO component clearly demonstrates the positive effect of nanocomposite formation on the electrochemical activity of metal oxides.