Revealing the synergistic mechanism of multiply nanostructured VO hollow nanospheres integrated with doped N, Ni heteroatoms, in-situ grown carbon nanotubes and coated carbon nanolayers for the enhancement of lithium-sulfur batteries.

Lithium sulfur (Li-S) batteries are regarded as one of the most promising future energy storage candidates on account of high theoretical specific capacity of 1675 mAh g and energy density of 2600 Wh kg. However, their practical application is seriously hindered due to the poor conductivity and volume expansion of sulfur, the weak redox kinetics of lithium polysulfide (LPS), and the severe shuttle effect of LPS. Herein, VO@N,Ni-C nanostructures, multiply integrated with zero-dimensional (0D) VO nanoparticles, 1D carbon nanotubes, 2D carbon coating layers and graphene, 3D hollow spheres, and doped N and Ni heteroatoms, were synthesized via a solvothermal method followed by chemical vapor deposition. After being used as a modifier for traditional commercial separator of Li-S batteries, the shuttle effect of LPS can be effectively suppressed owing to the abundant active physical and chemical adsorption sites derived from large specific surface area, rich porosity, and tremendous polarity of the VO nanoparticles with multiple secondary nanostructure integration. Meanwhile, the transfer of Li ions and electrons can be effectively enhanced by the highly conductive 2D carbon network, and the kinetics of redox reaction (LiS ↔ LiS) can be accelerated by the doped N and Ni heteroatoms, leading to a synergistic promotion on the reutilization of the adsorbed LPS. Additionally, the unique 3D hollow structure can not only enhance the penetration of electrolyte, but also buffer the volume expansion of sulfur to some extent. Therefore, the rate capacity and cycling performance can be significantly enhanced by the multifunction synergism of adsorption, conductivity, catalysis, and volume buffering. An initial discharge capacity of 1590.4 mAh gcan be achieved at 0.1C, and the discharge capacity of 803.5 mAh gcan be still exhibited when increasing to 2C. After a long period of 500 cycles, additionally, the discharge specific capacity of 1142.2 mAh g and capacity attenuation of 0.0617% per cycle can be obtained at 1C.