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.