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

Carbonaceous material with pores or bilayer spaces is 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 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 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 abilities in suppressing shuttle effect. Charge transfer occurs from Se8 and Li2Sen molecules to AA- and AB-stacking bilayer C2N, giving birth to the formation of strong Li-N bonds. The AA- and AB-stacking C2N-LiPSes systems possess high electrical conductivities, which is beneficial for high electrochemical performance. In addition, the reversible conversion mechanisms of Li2Sen in AA- and AB-stacking bilayer C2N are also investigated through the energy changes and decomposition reaction of 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 rate. Our present work could shed some lights on the possible strategy in designing highly efficient bilayer host materials for the higher performance Li-Se batteries.