Unveiling the potential of Mo2C and Mo2CO2 MXenes for Na-ion batteries: An ab initio study

This study employs density functional theory (DFT) calculations to investigate the potential of Mo₂C and Mo₂CO₂ MXenes as promising anode material candidates for Na-ion batteries under varying biaxial strains. The findings indicate that O-termination significantly enhances the Na adsorption energy compared to bare Mo₂C, due to a stronger O-Na interaction. Under compressive strain, the diffusion energy barrier decreases while it increases under tensile strain for both forms of Mo₂C-based MXenes. Ab initio molecular dynamics (AIMD) simulations at 300 K, which verify the thermal stabilities of both calculated MXenes, suggest their maximum theoretical capacities at operational temperatures, calculated to be 131.43 mAh/g for Mo₂C and 227.21 mAh/g for Mo₂CO₂. The open-circuit voltages (OCV) calculated from DFT total energies for the Na loadings retained after AIMD. The OVC is in the optimal range of 0–1.0 V, which helps prevent dendrite formation. The OCV values of 0.47 V for Mo₂C and 0.65 V for Mo₂CO₂ highlight their suitability as anodes. These results show that Mo₂C and Mo₂CO₂ have low energy barriers, high structural stability, and low OCV values, making them promising candidates for Na-ion battery anodes with properties that can be adjusted through biaxial strain modifications.