Iron(ii) molybdate (FeMoO4) nanorods as a high-performance anode for lithium ion batteries: structural and chemical evolution upon cycling

Abstract

FeMoO₄ nanorods were synthesized by a one-step solvothermal method and demonstrated to have attractive performance as an anode material in lithium ion batteries (LIBs). The specific capacity of the electrode exhibited an initial fading in the first 50 cycles and subsequently recovered to 1265 mA h g⁻¹ at about the 500^th cycle at a rate of 1C, after that, the capacity remained stable around 1110 mA h g⁻¹ until the 1000^th cycle. Based on comprehensive analysis of the structural and chemical evolution at each stage of capacity variation, we illustrated that the FeMoO₄ nanorods were converted to a Fe₂O₃/MoO₃ mixture after the first cycle and they experienced gradual structural variation of grain refinement and amorphization with their morphology transformed from nanorods to nanosheets upon cycling. Such changes in the chemical composition and microstructure of nanorods led to larger effective surface area, improved electrochemical reaction kinetics, and capacity retention capability. As a similar tendency of the specific capacity upon cycling has been widely observed for metal oxide anodes, studies on structural and chemical evolution of electrode materials during the whole cyclic life will be helpful for understanding their electrochemical reaction mechanism and provide guidance to material design and structural optimization of electrodes.