Electrochemical properties of core-shell structured NiO@SiO2 ultrafine nanopowders below 10 nm for lithium-ion storages

Ultrafine core-shell NiO@SiO2 nanopowders with various shell thicknesses were prepared by one-pot flame spray pyrolysis. The mean diameters of the NiO nanoparticles with 0, 2, and 5 wt% SiO2 were 13,10, and 9 nm, respectively. The coating of the NiO nanopowders with amorphous SiO2 was confirmed by transmission electron microscopy, zeta potential analysis, and X-ray photoelectron spectroscopy. The initial discharge capacities of the NiO nanopowders with 0, 2, and 5 wt% SiO2 at a current density of 1 Ag (1) were 1123, 1165, and 1145 mA h g (1), with corresponding initial Coulombic efficiencies of 66, 63, and 69%, respectively. The discharge capacities of the NiO nanopowders with 0, 2, and 5 wt% SiO2 after 150 cycles were 440, 669, and 554 mA h g (1), with capacity retentions from the second cycle of 58, 74, and 68%, respectively. The structural stability of the core-shell NiO@SiO2 nanoparticles during repeated Li charging and discharging improved the cycling and rate performances of the electrodes as compared with those containing bare NiO nanopowders. (C) 2015 Elsevier Ltd. All rights reserved.