Multifaceted insights into pentagonal BeP2 monolayer: From electrochemical to mechanical resilience for alkali-ion batteries using DFT

Abstract

Herein, we elucidated the properties of a pentagonal BeP2 monolayer, emphasizing its robust dynamic, thermal, and mechanical stabilities, as well as its promising electrochemical characteristics. Combining density functional theory (DFT) with a thermodynamic energy decomposition scheme, we identified BeP2 as a potentially excellent 2D material for energy storage devices. It is characterized by large lattice parameters and semi-metallic behavior, exhibiting a zero density of states (DOS) at the Fermi level. It demonstrates favorable open-circuit voltages, low metal ion migration barriers, and negligible structural modifications for Na and K ions. The specific capacities of Li/Na/K reached remarkable values, surpassing those of most previously reported monolayers. Emerging ion battery technology necessitates solid, directly comparable data to establish an optimized standard organic solvent electrolyte. With this objective in mind, we systematically investigated systems combining two Li/Na/K salts with three different alkyl carbonate solvents. Furthermore, we proposed a defect in BeP2 to explore all possible avenues for sustaining the pentagonal BeP2 monolayer (supplementary Fig. S5 and S6). In summary, our findings strongly indicate that the pentagonal BeP2 monolayer holds considerable promise as an anode material for sodium-ion batteries (NIBs) and potassium-ion batteries (KIBs) owing to its high electrochemical and mechanical sustainability and excellent compatibility with electrolytes.