Mechanistic insight into sodium intercalation dynamics and dual-functional electrocatalysis in 2D-FeS₂

The practical deployment of sodium-sulfur (Na-S) batteries, though economically attractive due to low material costs and high energy capacity, is compromised by two intrinsic limitations: the sodium-polysulfides (NaPSs) shuttle effect and inefficient Na-S redox kinetics, leading to rapid capacity fade. Regulating cathode materials is crucial for addressing the aforementioned challenges. An optimized sulfur host material serves a dual role: (i) suppressing NaPSs diffusion through strong chemisorption and (ii) catalytically accelerating the Na-S reaction kinetics, thereby fulfilling indispensable bifunctional requirements. The structural dynamics and bifunctional electrochemistry of 2D-Na_xFeS₂ (0 ≤ x ≤ 2) are studied using the first-principles calculations. 2D-Na_xFeS₂, as a sulfur cathode host, exhibits a robust discharge framework, an expansive voltage range (1.94-0.72 V), superior rate capability, substantial adsorption and catalytic performance. Lower voltage and adsorption energy are beneficial to the decomposition of Na₂S. This study establishes a robust theoretical framework for advancing research on the host materials of sulfur cathodes, while offering actionable insights into the rational design and optimization of next-generation high-performance Na-S batteries.