2D Ca2N/silicene donor-acceptor heterostructure with interstitial anionic electrons as anode material for lithium-ion batteries

Abstract

Two-dimensional (2D) donor-acceptor (D-A) heterostructures with strong bonding interfaces have recently attracted widespread attention due to their promoted catalytic and lithium/sodium storage properties compared with traditional van der Waals heterostructures. The utilization of 2D electride as a proficient donor material presents auspicious possibilities in the realm of anode material development for lithium-ion batteries (LIBs) due to the presence of excess interstitial anionic electrons (IAEs). In this work, through first-principles calculations, we propose a Ca2N/silicene D-A heterostructure as an anode material for LIBs. The Ca2N/silicene heterostructure exhibits metallic properties and structural integrity without structural deformation and large lattice expansion during lithiation. Compared to monolayer silicene, the migration barriers of lithium ion on the surface of heterostructure decrease by about 50% (from 0.23 eV to 0.12 eV), implying rapid charge/discharge process. Notably, the IAE states contribute to the adsorption behavior of more lithium ions and prevent the formation of dendritic deposits. Moreover, the variation in the work function of each layer results in the emergence of inherent dipoles in Ca2N/silicene heterostructure, thereby effectively augmenting the capacity for multilayer lithium storage and ion transport. All findings indicate that the Ca2N/silicene D-A heterostructure with IAE states is a promising LIBs anode material.