Combustion synthesized macroporous structure MFe2O4 (M= Zn, Co) as anode materials with excellent electrochemical performance for lithium ion batteries

ZnFe2O4 and CoFe2O4 materials are successfully prepared via solution combustion synthesis with glycine as fuel and complexing agent. The final products are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The average diameter of the prepared particles is in the range of 80-100 nm. Cyclic voltammetry (CV), galvanostatic cycling and electrochemical impedance spectroscopy (EIS) studies are used to investigate the electrochemical properties of the MFe2O4 (M = Zn, Co) particles. The reversible capacities of ZnFe2O4 and CoFe2O4 are 1037.2 mAh g−1 and 994.3 mAh g−1, respectively, after 80 cycles at a current density of 200 mA g−1. The capacity retentions are up to 104.2% and 106.6% compared to the second cycle. The as-synthesized samples also exhibit outstanding rate capability and long cycle life. After 300 cycles at a high current density of 1000 mA g−1, the capacity retention are 109.3% and 87.4% compared to the second cycle with almost no capacity fading but increasing. It could still maintain reversible capacities of 794.7 mAh g−1 and 746.5 mAh g−1, respectively. The superior electrochemical performance can be attributed to the macroporous structure in pure phase without any impurities, which can not only ease the volume expansion during the charge/discharge processes but also provide more interstices for lithium ions insertion. What is more, the high crystallinity of two samples is able to stabilize the microstructure no collapse after plenty of lithiation-delithiation processes. The results suggest that this method is a facile, effective and general way to synthesize excellent electrochemical properties of macroporous structure spinel Fe-based binary transition metal oxides as anode material for lithium ion batteries.