Hexagonal Boron Nitride with Vacancy Engineering as an Efficient Polysulfide Anchor and Electrocatalyst for Na-S Batteries

Abstract

Sodium-sulfur (Na-S) batteries have become a major focus of research because they can supply large amounts of energy at a minimal cost, depending on the natural abundance of sodium and sulfur. Despite these benefits, their widespread application remains limited because of several persistent issues, particularly brought on by the significant capacity loss caused by the dissolution of sodium polysulfides (NaPs) and the intrinsically sluggish reaction kinetics connected to their electrochemical conversion. In this work, we systematically analyzed the impact of vacancy-induced modifications in hexagonal boron nitride (h-BN) that enhance its catalytic performance and its ability to anchor sulfur species. Density functional theory calculations indicate that pristine h-BN interacts weakly with NaPs. On the other hand, introducing vacancy significantly enhances the interaction strength. Single nitrogen and single boron vacancies substantially boost the adsorption, and even stronger binding is attained when double nitrogen or double boron vacancies are created, thus lowering the polysulfide shuttle. The promise of vacancy-engineered h-BN as an efficient anchoring material is further demonstrated by the polysulfides' stronger binding to vacancy-engineered sheets compared to electrolyte molecules. The density of state calculations demonstrate that the h-BN lattice's electrical characteristics are much improved by the creation of vacancies, changing it from an insulating material to one with semiconducting or even semimetallic behavior. Overall, our results provide fundamental insights and demonstrate that vacancy-engineered h-BN is an excellent host material for reducing the shuttle effect in Na-S batteries because of its favorable electronic properties, structural robustness, and strong affinity for NaPs species.