Layered Symmetric Crystal Facets of Sulfur by Band Structure Modulation of SnS for Promoted Instantaneous Rate Capability of Li-S Batteries.

Facet engineering of sulfur is critical for optimizing polysulfide anchoring-catalytic conversion kinetics, enhancing electron/ion transport and enabling high instantaneous rate capability in lithium-sulfur batteries. However, conventional approaches face challenges like difficult synthesis of high-index crystal facets and inadequate facet orientation control. Herein, sulfur-doped carbon modifies the electronic structure of SnS, promoting preferentially oriented growth of layered sulfur with facets indexed as the crystallographically related (024) and (024̅) planes in sulfur-doped carbon/SnS/sulfur (named as SC/SnS/S) composites. Synchrotron radiation X-ray diffraction, together with HRTEM lattice-fringe measurement and software-indexed selected area electron diffraction, supports a preferential orientation and a symmetric crystallographic configuration involving the (024)/(024̅) sulfur planes. Both theoretical simulations and experimental results indicate that the crystallographically related sulfur facets are associated with abundant, uniform active sites and with improved ion/electron transport behaviour. Comparative analyses of catalytic parameters, including pseudocapacitive charge (Qpsc), active site density (ASD), and specific activity (SA), further indicate that symmetric crystal facet structures markedly enhance the anchoring-catalytic conversion capability toward polysulfides, substantially improving the high-rate capability (294 mAh·g-1 at 10C) of electrode materials. Based on the sulfur mass, the gravimetric energy density and power density of SC/SnS/S composite electrodes are 574.1 Wh/kg and 32.7 kW/kg, respectively. Under the laboratory coin-cell conditions employed here, SC/SnS/S composite electrodes exhibit promising high-rate performance, which supports facet regulation as a useful strategy for developing high-rate cathode materials.