"Electron-Sharing" Mechanism Promotes Co@CoO/CNTs Composite as the High-Capacity Anode Material of Lithium-Ion Battery.

Hybridization of nanostructured cobalt oxides with carbon nanotubes (CNTs) is considered to be an operative approach to harvest high-performance anode material for lithium-ion batteries (LIBs). On the other hand, there are numerous related works, most of which adopted a "post-combination" strategy, which is not only complicated but also ecologically unpromising for using toxic acid for surface modification of CNTs. Herein, we productively fabricate Co@CoO/CNTs nanocomposite with excellent conductivity through arc discharge following low-temperature oxidation in air. As the anode material for LIBs, this nanocomposite shows an exceedingly high reversible capacity of 820 mA h g at a current density of 0.2 A g after 250 cycles, much higher than its theoretical capacity. The rate performance of the material is also outstanding, with a capacity of 760 mA h g after 350 cycles at 1 A g (103% of the initial capacity) and 529 mA h g after 600 cycles at 2 A g. X-ray photoelectron spectroscopy tests are accomplished to disclose the true cause of extra capacity. And for the first time, we propose an "electron-sharing" storage mode, where extra electrons and Li can separate and be stored at the interface of cobalt metal/LiO. This not only gives a reasonable revelation for this unusual capacity exceeding the theoretical value but also directs the capacitor-like electrochemical behavior extra capacity.