Design and synthesis of yolk-shell FeO/N-doped carbon nanospindles with rich oxygen vacancies for robust lithium storage.

Ferric oxide (FeO) is an attractive anode material for lithium-ion batteries (LIBs) with a high theoretical capacity of 1005 mA h g. However, its practical application is greatly restrained by the rapid capacity fading caused by the large volume expansion upon lithiation. To address this issue, we have designed and synthesized a unique yolk-shell FeO/N-doped carbon hybrid structure (YS-FeO@NC) with rich oxygen vacancies for robust lithium storage. The obtained results show that YS-FeO@NC delivers a high reversible capacity of 578 mA h g after 300 cycles at a current density of 5 A g, about 11 times that (53.7 mA h g) of pristine FeO. Furthermore, a high specific capacity of 300.5 mA h g even at 10 A g is achieved. The high reversible capacities, excellent rate capability and cycle stability of YS-FeO@NC might be attributed to the elaborate yolk-shell nanoarchitecture. Moreover, electron percolation and a local built-in electric field induced by oxygen vacancies in the FeO matrix could also enhance the kinetics of Li insertion/deinsertion.