Mof-Derived Cofe2o4/Feo/Fe Nanocomposites as Anode Materials for High-Performance Lithium-Ion Batteries

Abstract

Due to the high theoretical capacity and low cost, iron-based oxides are considered to be valuable anode materials for lithium-ion batteries (LIBs) with applications. Its nanoscale design can effectively overcome the disadvantages of volume expansion and slow ion/electron transport rate. In this study, CoFe2O4/FeO/Fe three-phases composites nanospheres with ~10 nm diameter were prepared by high-temperature roasting using a Co-Fe MOF (metal organic framework) as the precursor. By adjusting the synthesis temperature, the ratio of each phase was changed and their electrochemical properties were investigated. Due to the synergistic effect of the multivalent states of iron, composites with optimal ratios (Fe-Co-700) can obtain capacities exceeding the theoretical limits (1129.8 mAh g-1 at 0.1 A g-1). Even at 2 A g-1 high current density, nanocomposites still show excellent properties (capacity of 1120.2 mAh g-1 after 500 cycles). In addition, the results show that the content of CoFe2O4 contributes significantly to the capacity, while the content of Fe has a positive effect on the electrical conductivity. According to the test of galvanostatic intermittent titration technique (GITT), the Li+ diffusion coefficient of Fe-Co-700 composite is larger than those of materials calcined at other temperatures. These excellent properties demonstrate the positive significance of phase ratio tuning of microstructures for the design of future energy storage materials.

Keywords: MOF derivative, Fe-based composite, Phase content, anode, Lithium-ion battery, CoFe2O4.