Understanding the anchoring and catalytic effect of the Co@C ₂ N monolayer in lithium–selenium batteries: a first-principles study

The practical applications of lithium-selenium (Li-Se) batteries are impeded due to the low utilization of active selenium, sluggish kinetics, and volume change. The development of highly efficient host materials to suppress high-order polyselenide shuttling and accelerate Li₂Se conversion is essential for Li-Se batteries. Herein, a theoretical design of a Co@C₂N monolayer as a host material for ultra-high areal capacity Li-Se batteries is proposed by first-principles calculations. The investigations of the lowest energy configurations, binding energies, and the charge transfer indicate that the Co@C₂N monolayer could alleviate the reciprocating motion of high-order polyselenides and improve the cycling performance. Further electronic property calculations show that the semi-metallic characteristics of the Co@C₂N monolayer material are retained even after chemical adsorption with Se₈ or Li₂Se_n molecules, which is beneficial for the utilization of active selenium. In addition, the crucial catalytic role of the Co@C₂N monolayer is investigated and the results indicate that the Co@C₂N monolayer could facilitate the formation and decomposition of Li₂Se molecules during the discharge and charge processes. Our present work would not only provide a deep understanding on the anchoring and catalytic effect of the Co@C₂N monolayer, but also demonstrate a general principle for the rational design and screening of advanced materials for high energy density Li-Se batteries.