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

Abstract

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 Li₂Se_n 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 Li₂Se_n 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.