Unlocking the potential of TiB5 monolayer as an appealing anode material for magnesium-ion batteries: A first-principles study

Abstract

Rechargeable magnesium-ion batteries (MIBs) have garnered extensive consideration as an exceptional alternative to lithium-ion batteries due to their high volumetric capacity, suitable reduction potential, good safety and low production cost; nonetheless, the lack of an outstanding anode material has significantly impeded the advancement of MIBs. Herein, we conducted a comprehensive first-principles calculation to assess the potential of a new-developed TiB₅ monolayer as an anode material for MIBs. The projected band structure and density of states calculations reveal that the resulting TiB₅ anode exhibits an intrinsic metallic behavior, primarily due to the B-band. Moreover, Mg ions are stably adsorbed on the TiB₅ anode surface with an adsorption energy of −2.09 eV and a slightly high diffusion barrier of 1.25 eV. Based on the charge density difference, Bader charge, crystal orbital Hamiltonian population (COHP) and crystal orbital bond index (COBI) calculations, it is found the main interaction between Mg and TiB₅ originates from the ionic Mg-B bonds. Remarkably, the TiB₅ anode demonstrates a high specific capacity of 1577.77 mA h/g, a low average open circuit voltage of 0.22 V and a small lattice expansion of 1.30 %, outperforming many reported 2D anodes. Additionally, the TiB₅ anode possesses excellent thermal stability without any Mg dendrite formation. These exceptional attributes highlight the potential of TiB₅ monolayer as a perspective anode material for MIBs.