Dynamic Intercalation-Conversion Site Supported Ultrathin 2D Mesoporous SnO/SnSe Hybrid as Bifunctional Polysulfide Immobilizer and Lithium Regulator for Lithium-Sulfur Chemistry.

The practical application of lithium-sulfur batteries is impeded by the polysulfide shuttling and interfacial instability of the metallic lithium anode. In this work, a twinborn ultrathin two-dimensional graphene-based mesoporous SnO/SnSe hybrid (denoted as G-mSnO/SnSe) is constructed as a polysulfide immobilizer and lithium regulator for Li-S chemistry. The as-designed G-mSnO/SnSe hybrid possesses high conductivity, strong chemical affinity (SnO), and a dynamic intercalation-conversion site (LiSnSe), inhibits shuttle behavior, provides rapid Li-intercalative transport kinetics, accelerates LiPS conversion, and decreases the decomposition energy barrier for LiS, which is evidenced by the XAS spectra, Raman, XRD, and DFT calculations. Moreover, the mesoporous G-mSnO/SnSe with lithiophilic characteristics enables homogeneous Li-ion deposition and inhibits Li dendrite growth. Therefore, Li-S batteries with a G-mSnO/SnSe separator achieve a favorable electrochemical performance, including high sulfur utilization (1544 mAh g at 0.2 C), high-rate capability (794 mAh g at 8 C), and long cycle life (extremely low attenuation rate of 0.0144% each cycle at 5 C over 2000 cycles). Encouragingly, a 1.6 g S/Ah-level pouch cell realizes a high energy density of up to 359 Wh kg under a lean E/S usage of 3.0 μL mg. This work sheds light on the design roadmap for tackling S-cathode and Li-anode challenges simultaneously toward long-durability Li-S chemistry.