Dynamic Intercalation–Conversion Site Supported Ultrathin 2D Mesoporous SnO₂/SnSe₂ Hybrid as Bifunctional Polysulfide Immobilizer and Lithium Regulator for Lithium–Sulfur Chemistry

Abstract

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 SnO₂/SnSe₂ hybrid (denoted as G-mSnO₂/SnSe₂) is constructed as a polysulfide immobilizer and lithium regulator for Li-S chemistry. The as-designed G-mSnO₂/SnSe₂ hybrid possesses high conductivity, strong chemical affinity (SnO₂), and a dynamic intercalation-conversion site (Li_<i>x</i>SnSe₂), inhibits shuttle behavior, provides rapid Li-intercalative transport kinetics, accelerates LiPS conversion, and decreases the decomposition energy barrier for Li₂S, which is evidenced by the <i>ex situ</i> XAS spectra, <i>in situ</i> Raman, <i>in situ</i> XRD, and DFT calculations. Moreover, the mesoporous G-mSnO₂/SnSe₂ with lithiophilic characteristics enables homogeneous Li-ion deposition and inhibits Li dendrite growth. Therefore, Li-S batteries with a G-mSnO₂/SnSe₂ separator achieve a favorable electrochemical performance, including high sulfur utilization (1544 mAh g^-1 at 0.2 C), high-rate capability (794 mAh g^-1 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^-1 under a lean E/S usage of 3.0 μL mg^-1. This work sheds light on the design roadmap for tackling S-cathode and Li-anode challenges simultaneously toward long-durability Li-S chemistry.