Preparation and electrochemical properties of hollow carbon spheres/sulfur co-doped with N and O for high-performance lithium-sulfur batteries

Hollow Carbon Spheres co-doped with nitrogen(N) and oxygen(O) (NOHCS) with high specific surface area (422 m(2) g(- 1)) have been successfully fabricated through calcination and carbonization in nitrogen gas in the presence of SiO2 nanoparticles as the templating agent, phenolic resin as the carbon precursor, and melamine as the nitrogen precursor. The material has hierarchical porous structure, hollow frame and synergistic effect of N and O, which can alleviate the volume expansion effect, increase the sulfur load, significantly improve the conductivity of carbon material, and effectively alleviate the shuttle effect of lithium-sulfur battery. The NOHCS/S-0.12 composite material has a very high initial discharge capacity of 1029 mAh g(- 1) and a specific capacity of 541 mAh g(- 1) after 200 cycles at 0.1 C, showing good cycling stability. It has strong electrochemical reversibility and small electrochemical impedance of the cell, which shows electrode polarization of only 0.38 V. These results indicate that the hollow structure has a synergistic effect with N and O co-doping, effectively limiting the dissolution and diffusion of polysulfide. N-O co-doped hollow carbon spheres have good development potential in the application of lithium-sulfur batteries.