Polysulfide barrier comprising bismuth selenide nanocrystals well anchored within N-doped carbon microspheres for stable Li-S batteries

The development of functional interlayers to effectively anchor lithium polysulfide (LiPS) and enhance the integrity of sulfur cathodes in lithium-sulfur (Li‒S) batteries has received significant global consideration. However, identifying an interlayer that is both highly conductive and structurally robust remains a major challenge. This study presents the synthesis of three-dimensional nitrogen-doped carbon microspheres embedded with bismuth selenide nanocrystals (referred to as “3D Bi₂Se₃@N‒C” microspheres) and evaluates their role as a polysulfide barrier for enhanced Li‒S battery performance. The embedded Bi₂Se₃ nanocrystals within the microspheres provide numerous active spots for chemical captivity and electrocatalytic transformation of lithium polysulfide species. Moreover, the N-doped carbon framework facilitates speedy transfer of charge moieties, resulting in faster redox activity. Correspondingly, cells paired with 3D Bi₂Se₃@N‒C microsphere modified separator exhibit excellent rate capability (297 mA h g⁻¹ at 2.0 C-rate) and prolonged stable cycling performance at different C-rates (863 mA h g⁻¹ after 100 cycles at 0.1 C, 440 mA h g⁻¹ after 200 cycles at 0.5 C, and 219 mA h g⁻¹ after 500 cycles at 2.0 C). The cell demonstrates satisfactory cycling performance retaining 57% of its capacity after 200 cycles when the active material loading was raised to 3.5 mg cm⁻², confirming the practical feasibility of the prepared nanostructure. The detailed physical and electrochemical results presented in this study offer valuable perceptions for the expansion of structurally superior, conductive, and easily scalable nanostructures for a variety of energy storage demands.