Unraveling the superior anchoring of lithium polyselenides to the confinement bilayer C2N: an efficient host material for lithium-selenium batteries.

Carbonaceous materials with pores or bilayer spaces are a kind of potential host material to confine polyselenide diffusion and mitigate the shuttling effect. In the present work, a theoretical design of bilayer C2N (bi-C2N) as an efficient host material for lithium-selenium (Li-Se) batteries was explored by first-principles calculations. AA- and AB-stacking bilayer C2N could alleviate the dissolution of high-order polyselenides through a synergistic effect of physical confinement and strong Li-N bonds. Lithium polyselenides prefer to anchor on AA- and AB-stacking bilayer C2N instead of the commonly used electrolytes, showing their capabilities in suppressing the shuttle effect. Charge transfer occurs from Se8 and Li2Sen molecules (LiPSes) to AA- and AB-stacking bilayer C2N, giving rise to the formation of strong Li-N bonds. The AA- and AB-stacking LiPSes@C2N systems possess high electrical conductivities, which is beneficial for high electrochemical performance. In addition, the reversible conversion mechanisms of Li2Sen in the AA- and AB-stacking bilayer C2N are also investigated through the energy changes and decomposition reaction of the Li2Se molecule, and the results indicate that AA- and AB-stacking bilayer C2N facilitate the formation and decomposition of Li2Se by decreasing the active energy barriers and improving the selenium utilization rates. Our present work could shed some light on a possible strategy for designing highly efficient bilayer host materials for high performance Li-Se batteries.