l-cysteine-assisted preparation of porous NiO hollow microspheres with enhanced performance for lithium storage
Porous NiO hollow microspheres have been synthesized via a simple hydrothermal process using L-cysteine as a structure-directing agent followed by calcination. The as-synthesized NiO microspheres are hollow with diameters of 2–3 μm. The shells of the microspheres are built from nanoparticles with diameters of 30–50 nm, and the interior cavities are around 0.75 μm in diameter. A plausible mechanism has been proposed to explain the formation of the porous NiO hollow spheres. When evaluated as anode materials for lithium ion batteries, the porous NiO hollow microspheres show outstanding electrochemical performances, including high reversible capacity of 847.2 mAh g−1 after 50 cycles at 100 mA g–1, high rate capability with a discharge capacity of 470 mAh g−1 at a current density of 800 mA g−1, and good cycling stability. The excellent lithium-storage performance can be attributed to the porous hollow architectures, which provide fast ion/electron transfer and the structural flexibility for volume change during the cycling process.