First-Principles Study of Two-Dimensional M₂B₂ (M = Mo, Cr, Ti) Materials as Anodes for Zinc-Ion Batteries

Two-dimensional transition metal borides (MBenes) have demonstrated outstanding electrochemical properties, making them highly promising candidates for energy storage applications. To enhance the anode performance of rechargeable zinc-ion batteries (ZIBs), this study employs first-principles calculations to systematically investigate the application potential of orthorhombic (o-M₂B₂) and hexagonal (h-M₂B₂) phases of Mo₂B₂, Cr₂B₂, and Ti₂B₂. The results reveal that both o-M₂B₂ and h-M₂B₂ structures are thermodynamically stable and possess good electrical conductivity. For the same transition metal (M), o-M₂B₂ and h-M₂B₂ exhibit identical maximum zinc intercalation concentrations, corresponding to theoretical capacities of 502.03 mA·h·g⁻¹ for Mo₂B₂, 853.40 mA·h·g⁻¹ for Cr₂B₂, and 913.46 mA·h·g⁻¹ for Ti₂B₂. Notably, Cr₂B₂ and Ti₂B₂ offer significantly higher theoretical capacities compared to conventional zinc anodes. In addition, Zn atoms exhibit very low diffusion barriers on h-Mo₂B₂ (84 meV), h-Cr₂B₂ (82 meV), h-Ti₂B₂ (76 meV), and o-Ti₂B₂ (206 meV), indicating excellent ion transport properties. These findings suggest that two-dimensional M₂B₂ (M = Mo, Cr, Ti) materials are highly promising anode candidates for ZIBs.