A‐Site Spin‐State Engineering in Antiperovskites for Enhanced Polysulfide Adsorption and Sulfur Redox Catalysis

ABSTRACT Lithium‐sulfur batteries (LSBs) possess exceptionally high theoretical energy density and specific capacity, making them promising candidates for next‐generation energy storage systems. However, the sluggish adsorption and catalytic conversion kinetics of lithium polysulfides severely hinder their practical application. In this work, a functional separator modified with antiperovskite nitride (IZNC) was developed. The precise incorporation of In at the antiperovskite. A‐site regulation effectively modulated the spin state of Co active sites, inducing a low‐spin to high‐spin transition of Co ions and thereby enhancing their affinity for polysulfides. Furthermore, the antiperovskite transformed the conventional two‐dimensional Li 2 S deposition behavior into a mixed 2D/3D growth mode, Such altered deposition morphology facilitates Li 2 S nucleation‑growth kinetics and enhances the overall reaction reversibility of the sulfur cathode. Consequently, the assembled cell exhibited outstanding cycling stability, with an average capacity decay of only 0.06% per cycle over 600 cycles at 1 C. Moreover, even at a high sulfur loading of 4.3 mg cm −2 , an impressive areal capacity of 6.1 mAh cm −2 was achieved. This work provides valuable insights into the rational design of functional separators for high‐performance LSBs.