Enhanced catalytic conversion of polysulfides using high-percentage 1T-phase metallic WS2 nanosheets for Li–S batteries

Abstract

High-energy-density lithium-sulfur batteries has attracted substantial attention as competitive candidates for large-scale energy storage technologies. Still, the adverse “shuttle effect” and sluggish sulfur conversion reaction kinetics immensely obstruct their commercial viability. Herein, a two-dimensional metallic 1T phase WS2 (1T-WS2) nanosheets modified functional separator is developed to improve the electrochemical performance. Meanwhile, the semiconducting bulk-WS2 crystals, and 2H phase WS2 (2H-WS2) nanosheets with more basal-plane S-vacancy defects are also prepared to probe the contributions of the crystal structure (phase), S-vacancy defects, and edges to the Li–S batteries performance experimentally and theoretically. In merits of the synergistic effect of high ion and electron conductivity, enhanced binding ability to lithium polysulfides (LiPSs), and sufficient electrocatalytic active sites, the 1T-WS2 shows highly efficient electrocatalysis of LiPSs conversion and further improves Li–S battery performance. As expected, thus-fabricated cells with 1T-WS2 nanosheets present superior cycle stability that maintain capacity decline of 0.039% per cycle after 1000 cycles at 1.0 C. The strategy presented here offers a viable approach to reveal the critical factors for LiPSs catalytic conversion, which is beneficial to developing advanced Li–S batteries with enhanced properties.

Keywords

• Li–S batteries
• Electrocatalysts
• Polysulfides
• WS2