N-doped hollow carbon nanospheres as sulfur hosts for high performance Li-S batteries

SiO₂@C nanospheres were fabricated by polymerization of dopamine in the presence of tetraethyl orthosilicate followed by carbonization and the SiO₂ was chemically etched away to obtain hollow N-doped carbon nanospheres (N-CNs) to host sulfur. The resulting material (S@N-CNs) was used as the cathode material of a Li-S battery. Results indicate that the S@N-CNs can effectively suppress the volume expansion of sulfur and the shuttle effect of polysulfides during charge and discharge. Nitrogen doping improves the electrical conductivity of the N-CNs. The initial reversible capacity of the S@N-CN electrode at 0.2 C is 1 179 mAh·g^-1, which remains at 540 mAh·g^-1 after 100 cycles. The electrode has excellent rate capability (343 mAh·g^-1 at 1 C and 247 mAh·g^-1 at 2 C).