Investigation of 2D Nb3C2-Based MXenes as the Anode Material for LIBs: A Theoretical Study

Abstract

MXenes, two-dimensional transition metal carbides/nitrides, have gained substantial interest owing to their distinctive properties. This study utilizes density functional theory (DFT) calculations to study the electronic, magnetic, and thermoelectric properties of pristine, molybdenum (Mo), and Te-doped Nb₃C₂ monolayer MXenes. Both doped structures exhibit metallic characteristics with indirect band gaps, as revealed by band structure and density of states (DOS) analysis. This fulfills a crucial requirement for electrode applications in lithium-ion batteries (LIBs). Pristine Nb₃C₂ displays diamagnetic, while Mo doping induces ferromagnetism and Te doping leads to ferrimagnetism behavior. Notably, doping significantly impacts electronic and thermoelectric properties, Seebeck coefficient, electrical conductivity, and thermal conductivity, which demonstrably depend on the chosen structure. Te-doped Nb₃C₂ consistently exhibits a larger bandgap, less Seebeck coefficient, and lower thermal conductivity compared to Mo-doped Nb₃C₂ attributed to a narrow bandgap, exceptionally high Seebeck coefficient, and high thermal and electrical conductivity. Additionally, positive open-circuit voltage (OCV) values suggest favorable lithium-ion intercalation for all materials. Theoretical capacities of 592, 745, and 668 mAh/g are computed for pristine, Mo-doped, and Te-doped Nb₃C₂, respectively, comparable to reported values for pristine V₃C₂ (606.42 mAh/g). These results suggest that Mo- and Te-doped Nb₃C₂ MXenes exhibit potential as anode materials for LIBs due to their improved electronic conductivity, reduced operating voltage, and comparable theoretical lithium storage capacity.