Two-dimensional AlB4/Al2B2: high-performance Dirac anode materials for sodium-ion batteries

Abstract

Sodium-ion batteries (SIBs) have attracted much attention due to their abundant earth-reserves and low cost. Two-dimensional (2D) Dirac materials show great application prospects as anodes for SIBs because of their excellent electronic conductivity. We explore the performances of AlB₄ (Al₂B₂) monolayers and bilayers as anodes for SIBs by using first-principles calculations. The AlB₄ (Al₂B₂) monolayer exhibits a high theoretical storage capacity of 954.15 (709.17) mA h g⁻¹ and a low diffusion barrier of 0.36 (0.03) eV. The calculated average open-circuit voltage (0.68/0.18 V) falls within the acceptance range of 0.1–1.0 V for anode materials. The fully sodiated AlB₄ (Al₂B₂) monolayer shows a tiny lattice expansion of 0.9% (2.4%), suggesting good reversibility. Furthermore, in comparison with the AlB₄ (Al₂B₂) monolayer, the AlB₄ (Al₂B₂) bilayer can provide stronger binding with Na on the outside surface. These results contribute to a better understanding of the AlB₄ (Al₂B₂) monolayers and bilayers as potential high-performance anode materials for SIBs.