Emcoating Architecture Construction via CO 2 /H 2 Coupling Treatment Doubles Reversible Capacity of NbO 2 /C Anode.

As a promising alternative as lithium-ion anode, niobium dioxide appeals to researchers due to high theoretical capacity and good electron conductivity. However, rarely work about NbO 2 based high performance anode is reported. Here, NbO 2 nanoparticles emcoated in continuous carbon matrix is constructed through CO 2 /H 2 coupling treatment. CO 2 activation introduces unique carbon emcoating structure, which builds interconnected electron conductive network with low carbon content. Furthermore, crystallographic phase of NbO 2 is enhanced during H 2 treatment, which increases the lithium storage ability. Electrochemical performance of NbO 2 anodes is significantly improved based on the carbon emcoating structure. A high reversible capacity of 391 mAh g -1 is retained after 350 cycles at 0.2 C. Additionally, at a current density of 1 A g -1 , the reversible capacity reaches 139 mAh g -1 . Compared with conventional NbO 2 /C nanohybrids, the lithium diffusion coefficient of carbon-emcoated sample shows improvement of three orders of magnitude. Moreover, the in situ XRD investigation shows a reversible lithium insertion behaviour with a limited volume change.