Evaluating the potential of planar checkerboard lattice Cu₂N monolayer as anode material for lithium and sodium-ion batteries using first-principles methods

We present first-principles insights into the electrical and electrochemical properties of Cu₂N, a newly synthesized two-dimensional material that features a planar, checkerboard lattice structure [Hu et al., Nano Lett. 2023, 23 (12), 5610–5616]. We evaluate the suitability of monolayer Cu₂N as an anode material for Li and Na-ion batteries by examining its storage capacity, diffusion barrier, open-circuit voltage (OCV), volume expansion, and the impact of defects on its electrochemical performance. The monolayer Cu₂N demonstrates a storage capacity of 379.88 mAh.g⁻¹ for both Li and Na, comparable to that of commercial graphite for Li (372 mAh.g⁻¹) and significantly higher for Na (less than 35 mAh.g⁻¹). The migration barriers for Li and Na are found to be 0.1 eV and 0.01 eV, respectively, substantially lower than those theoretically reported for commercial anodes TiO₂ (0.4–1.0 eV) and graphite (∼0.4 eV), which imply that monolayer Cu₂N demonstrates excellent charge/discharge capabilities. Moreover, the volume growth of monolayer Cu₂N is 4.14 % with maximal Li adsorption, which is 2.4 times less than graphite. The analysis of vacancy defects reveals a significant enhancement in the binding energies of Li and Na atoms, accompanied by minimal changes in diffusion barriers. Since monolayer Cu₂N has already been successfully synthesized, these findings would pave the way for large-scale experimental fabrication of monolayer Cu₂N as a battery anode.