The synthesis of NiO/C nanocapsules with NiO nanoparticles as the core and onion-like carbon layers as the shell is reported. The NiO/C nanocapsules deliver an initial discharge capacity of 1689.4 mAh g-1at 0.5 C and maintain a high reversible capacity of 1157.7 mAh g-1after 50 cycles compared to the NiO nanoparticles of 383.5 mAh g-1. As an anode material for lithium ion batteries, the NiO/C nanocapsules exhibit a remarkable discharge capacity, a high rate charge-discharge capability and an excellent cycling stability. The improvements are ascribed to the fact that the onion-like carbon shells not only can provide enough voids to accommodate the volume change of NiO nanoparticles but also can prevent the formation of solid electrolyte interface (SEI) films on the surface of the NiO nanoparticles and hence the direct contact of Ni and SEI films upon lithium extraction.
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