Three-dimensional structural confinement design of conductive metal oxide for efficient sulfur host in Lithium-sulfur batteries

Abstract

The design of sulfur hosts with good conductivity, stable hierarchical porosity, and highly active sites is essential for efficient lithium-sulfur (Li-S) batteries. In this study, a porous structured conductive Nb-doped and oxygen-deficient TiO2 (Nb-TiO2−x) is developed to serve as high-performance sulfur host. The introduction of oxygen vacancies and Nb-doping not only benefits the electrical conductivity of the oxide matrix, but also promotes the lithium polysulfide (LiPS) trapping and catalytic conversions. Moreover, the Nb-TiO2−x host matrix is designed into a three-dimensional ordered macroporous (3DOM) skeleton implemented with microporous N-doped carbon (NC) fillers. The 3DOM framework provides large and stable space for sulfur accommodation, whereas the hollow NC polyhedrons afford additional microsporosity and active sites for sulfur confinement. Benefited from these unique superiorities, the NC@Nb-TiO2−x-based sulfur cathode exhibits a capacity fading rate of 0.025 % per cycle in 1000 cycles, and a 8.06 mAh cm−2 areal capacity at a raised sulfur loading of 8.0 mg cm−2 in coin-cell configuration. Moreover, the corresponding pouch cells demonstrate decent workability at flexible scenario as well as stable cycling behavior under 3.5 mg cm−2 sulfur loading and electrolyte-to-sulfur (E/S) ratio of 9.5 μL mg−1. This work provides a feasible pathway towards efficient and durable Li-S batteries.