Insights into the halogen-induced p-band center regulation promising high-performance lithium-sulfur batteries

Sn-based halide perovskites are expected to solve the problems of the shuttle effect and sluggish redox kinetics of lithium polysulfides (LiPSs) in lithium-sulfur batteries (LSBs) due to their high conductivity and electrocatalytic activity, but their intrinsic catalytic mechanism for LiPSs remains to be explored. Herein, halide perovskites with varying halide anions, Cs₂SnX₆ (X = Cl, Br, I), are purposefully designed to unveil the halogen-induced regulatory mechanism. Theoretical calculations demonstrate that increasing the halogen atomic number induces the shift of the p-band center closer to the Fermi level, which results in the localized charge distribution around halide anions and rapid charge separation/transfer at Sn sites, enhancing the adsorptive and catalytic activity and redox kinetics of LiPSs. Experimental investigations exhibit that LSBs assembled with the Cs₂SnI₆ modified separator deliver a high initial capacity of 1000 mA h g^-1 at 2C, with a minimum decay rate of 0.068% per cycle after 500 cycles. More impressively, the Cs₂SnI₆ battery with a high sulfur loading (6.1 mg cm^-2) and a low electrolyte/sulfur ratio (5.5 μL mg^-1) achieves a remarkable reversible capacity of 768.8 mA h g^-1, along with robust wide-temperature-tolerant cycling performance from -20 to 50 °C. These findings underscore the critical role of p-band center regulation in rationally designing advanced LSBs.