Two-dimensional boron-rich BxN as a potential electrode for synergistic immobilization and catalysis of lithium polysulfides: A first-principles investigation

Lithium-sulfur batteries show high promise as the next-generation energy storage systems due to their impressive energy density, cost-effectiveness, and environmentally friendly characteristics. However, the well-known shuttle effect and the sluggish conversion dynamics of lithium polysulfides (LiPSs) during discharging and charging processes hinder their practical application. Herein, we investigate the potential of two-dimensional boron-rich BxN (x=2, 3, and 5) as a viable additive to enhance the anchoring of soluble LiPSs and improve the LiPSs conversion dynamics by harnessing the flexible B-N cooperative interactions. Through density functional calculations, we demonstrate that these BxN electrodes exhibit desirable anchoring ability towards soluble lithium polysulfides (LiPSs) in a realistic solution environment by employing explicit solvent molecules in conjunction with an implicit solvent model. Furthermore, B3N and B5N exhibit robust electrocatalytic activity in both the sulfur reduction and LiPSs decomposition reactions. Intriguingly, a novel cross-sheet mechanism was discovered in B2N, 2 N, characterized by an Ebarrier of 0.27, 0.20, 0.40, 0.37 and 0.49 eV for the decomposition of Li2S, 2 S, Li2S2, 2 S 2 , Li2S4, 2 S 4 , Li2S6 2 S 6 and Li2S8, 2 S 8 , attributed to its distinctive configuration with a large eight-ring structure. Additionally, the introduction of BxN x N can significantly alleviates the volumetric changes experienced by the sulfur cathode during the charging and discharging processes. BxN x N is a promising catalyst for boosting the electrochemical conversion processes of LiPSs in Li-S batteries and exhibit desirable anchoring ability for inhibiting the shuttle effect induced by soluble LiPSs. These findings offer an alternative approach for the development of advanced sulfur cathode catalysts with reduced shuttle effects and improved rate performance.