Heterostructured TiN/TiO2 on the hierarchical N-doped carbon for enhancing the polysulfide immobilization and sulfur reduction in lithium-sulfur battery

The commercialization of lithium-sulfur batteries (LSBs) is impeded by their low sulfur utilization and poor cycling stability. Herein, uniformly distributed TiN/TiO2 heterostructures on the hierarchical nitrogen-doped inter-connected multi-scale porous carbon matrix was developed as an effective polysulfide trapper and catalytic accelerator for sulfur reduction reaction. The performance of synthesized TiN/TiO2 heterostructures in LSBs are compared with those of TiN and TiO2. The synergetic effects of strong polysulfide adsorption of TiO2 and superior catalytical conversion ability of TiN draw rapid trap-diffusion-conversion process and enhance the reaction kinetics. This heterostructure-based LSBs exhibit a high specific capacity of 1458.5 mAhg−1 at 0.1 C and 684.9 mAhg−1 at 5 C. Over 1000 cycles, a high capacity of 576 mA h g−1 is retained with a low-capacity decay of 0.030 % per cycle at 2 C. Moreover, a high area capacity value of 6.65 mAh cm−2 is obtained at 0.5C with a high sulfur loading of 8.2 mg cm−2 and low electrolyte/sulfur ratio (E/S) of 4.7. This study provides a novel strategy to develop the transition metal nitride-oxide heterostructure on a three-dimensional porous carbon framework as efficient electrode materials for LSBs application.