Interconnected porous N-doped carbon coated cobalt/iron oxides core shell nanocomposites for superior lithium storage anode

Abstract

The design and fabrication of transition metal oxides (TMOs) anode with superior lithium storage performance remains a challenge. Herein, we demonstrate one-pot hydrothermal method combined with post-calcination for the construction of interconnected porous N-doped carbon-coated cobalt/iron oxides nanocomposite (CFO@N-C) as lithium-ion batteries (LIBs) anode. This facile approach gives CFO@N-C many interesting characters such as rich porous structure, fine cobalt/iron oxides’ nanocrystals (<10 nm), interconnected carbon coating layer (~3–20 nm) and high nitrogen content (33.2 wt%, N/C). When evaluated as LIBs anodes, it rendered a reversible capacity of about 1218 mAh g−1 at 0.2 A g−1 after 100 cycles, a remarkable discharge capacity of about 376.8 mAh g−1 was retained after 400 cycles even at current density of 10 A g−1. Cyclic voltammetry revealed there exists a notable capacitive contribution, especially at high rate (74.2% at ~5C). Electrochemical impedance spectroscopy disclosed that CFO@N-C electrode possesses not only a low charge transfer resistance, but also a high Li diffusion coefficient, about 60 times that of pure cobalt ferrite electrode.