Exploring the anchoring mechanism of polyselenides on C4N3 monolayer as selenium host material: A first-principles study

Lithium-Selenium (Li-Se) batteries encounter several challenges, including low active Se utilization, slow kinetics, volume expansion during charging and discharging, and the shuttle effect of high-order polyselenides. The development of high-performance selenium host materials is essential to suppress the shuttle effect of high-order polyselenides and increase the Li2Se conversion rate. In this regard, a theoretical design of C4N3 monolayer as the potential host material for Li-Se batteries is proposed through first-principles calculations. The analysis of the lowest energy configuration, binding energy, and charge transfer shows that the C4N3 monolayer can inhibit the solubilization of high-order polyselenides by creating the strong Li-N bonds. Compared to conventional electrolytes, the polyselenides are more readily adsorbed on the surface of C4N3 monolayer, which effectively inhibits the shuttling of high-order polyselenides and improves cycling stability. The catalytic role of the C4N3 monolayer was evaluated in terms of the reduction pathway of Se8 and decomposition barrier of Li2Se. The results showed that C4N3 could promote the formation and decomposition of Li2Se molecule during the discharge and charge processes and improve the utilization of selenium active material. Our current study not only offers a theoretical understanding of the anchoring and catalytic roles of C4N3 monolayer but also provides valuable insights into the general principles for investigating C4N3-based host materials for Li-Se batteries.