γ-Fe₂O₃@CNTs Anode Materials for Lithium Ion Batteries Investigated by Electron Energy Loss Spectroscopy

Abstract

Atomic layer deposition was employed to deposit maghemite (γ-Fe 2 O 3 ) nanoparticles on carbon nanotubes (CNTs) to prepare the γ-Fe 2 O 3 @CNTs composites, which exhibit a superior lithium storage performance as the anode of lithium ion batteries (LIBs). The high reversible capacity of 859.7 mA h/g was observed after 400 cycles at a current density of 500 mA/g. Even at the high current density of 10000 mA/g, the specific cyclic capacity of 464.4 mA h/g can still be obtained. Furthermore, electron energy loss spectroscopy results reveal that the Fe chemical state plays a critical role in the evolution of the capacity of γ-Fe 2 O 3 @CNTs composite anodes during the cycling process. The incomplete conversion of the chemical state in γ-Fe 2 O 3 reduces the capacity, while the recovery of the chemical state of γ-Fe 2 O 3 during the cycling process may cause the increase in capacity. This work provides insight into understanding the detailed working mechanism of transition metal oxides in LIBs, which helps in the design of electrode materials with promising lithium storage performance.