Carbon paper with attached hollow mesoporous nickel oxide microspheres as a sulfur-hosting material for rechargeable lithium-sulfur batteries

Hollow nickel hydroxide microspheres built of nanosheets could be obtained by hydrothermal synthesis in the presence of glycine. After heating to 400 °C in air, the hexagonal β-Ni(OH)2 was converted into cubic NiO which showed better electrical conductivity and greater surface area compared with other annealing temperatures. The surface morphology remained almost unchanged, while the Ni(OH)2 nanosheets with solid interior were changed into NiO nanosheets composed of interconnected nanoparticles and mesopores after annealing at 400 °C. The sulfur-filled hollow mesoporous NiO microspheres obtained after annealing at 400 °C was loaded into the carbon paper as cathode (NiO/S) for lithium-sulfur batteries. The NiO/S cathode could deliver a large specific capacity of 1300 mAh g−1 at 0.2C (335 mA g−1), much greater than bare sulfur loaded into the carbon paper (1000 mAh g−1). Moreover, the NiO/S cathode showed superior capacity recovery after C-rate test and coulombic efficiency during cycling test than S cathode. The improved performance for NiO/S could be attributed to the conductive NiO microspheres with mesoporous nanosheets that provided intimate electrical contact for boosting the charge-transfer reaction between lithium ions and sulfur materials, limited the polysulfide shuttle, and buffered volumetric expansion/contraction during charging and discharging. •Hollow NiO microspheres are coated on carbon paper as a sulfur-hosting material.•An optimum annealing temperature for hollow NiO microspheres is found to be 400 °C.•Sulfur can be filled in hollow mesoporous NiO microspheres by melt-diffusion process.•The NiO/S cathode delivers a high specific capacity of 1300 mAh g−1 at 0.2C current.•The NiO/S shows superior capacity recovery and coulombic efficiency than S cathode.