Hollow carbon spheres with TiO2 encapsulated sulfur and polysulfides for long-cycle lithium-sulfur batteries

HC-TiO2/S composite (Hollow carbon spheres with TiO2 in or out the carbon spheres encapsulates sulfur and polysulfides) is successfully prepared in our study. The hollow carbon spheres own good electrical conductivity and hollow volume, which can remedy the defect of nonconductive sulfur species and restrain the volumetric expansion of sulfur, respectively. And the TiO2 has strong interaction with sulfur species and polysulfides, which can suppress the diffusion of polysulfide intermediates. TGA indicates that the HC-TiO2 can be loaded with 67 wt % sulfur. Based on the synergistic effect of hollow carbon spheres and nano TiO2, the HC-TiO2/S cathode can deliver a discharge specific capacity of 671 mAh/g at 1 C (1 C = 1672 mA/g) after 300 cycles, together with the capacity retention of 93%.