Two-dimensional phosphorus carbides (β-PC) as highly efficient metal-free electrocatalysts for lithium-sulfur batteries: a first-principles study.

Li-S batteries are considered as the next-generation batteries due to their exceptional theoretical capacity. However, their practical application is hampered by the shuttling effects of lithium polysulfides (LiPSs) and the sluggish Li 2 S decomposition, particularly the slow conversion from Li 2 S 2 to Li 2 S. Addressing these challenges, the quest for effective catalysts that can accelerate the conversion of LiPSs and enhance the performance of Li-S batteries is crucial. In this study, we explored the electrocatalytic activity of two-dimensional phosphorus carbides (β 0 -PC and β 1 -PC) in Li-S batteries based on first-principles calculations. Our findings reveal that these materials demonstrate optimal binding strengths (ranging from 1.09 to 1.83 eV) with long-chain LiPSs, effectively preventing them from dissolving into the electrolyte. Additionally, they show remarkable catalytic activity during the sulfur redox reaction (SRR), with Δ G being only 0.37 eV for β 0 -PC and 0.13 eV for β 1 -PC. The low energy barrier induced by β-PC enhances ion migration barrier and significantly expedites the charge/discharge cycles of Li-S batteries. Furthermore, we investigated the conversion dynamics of Li 2 S 2 to Li 2 S, employing the computational lithium electrode (CLE) model. The excellent performance in these aspects underscores the potential of these materials as electrocatalysts for Li-S batteries, paving the way for advanced high-efficiency energy storage solutions.