Nb2C and Nb2CO2 MXenes as Anodes in Li-ion Batteries: A Comparative Study by First-Principles Calculations

Abstract Resume: The new generation of Li-ion batteries is based on integrating 2D materials into the electrodes to increase energy density while reducing charging time and size. The two-dimensional transition metal carbides or nitrides (MXene) materials offer ideal electronic properties such as metallic behavior, low energy barriers for Li-ion diffusion, and structural stability. This study focuses on Nb2C and Nb2CO2 MXenes, which have shown promising Li-storage capacity, especially the oxidized phase. By using Density Functional Theory (DFT) and thermodynamics criteria, we study the Li intercalation process in both MXenes. Results show that the Li intercalation process in the oxidized phase is more stable. Also, the Li diffusion barriers are 35 meV and 250 meV for the bare and oxidized phase, because of the strong interaction between Li ions and O functional groups. Nb2C and Nb2CO2 MXenes deliver a maximum gravimetric theoretical capacity of 275 and 233 mAh/gr, respectively, with a stable performance.