Theoretical investigation of Mo2C and Mo2CO2 as anodes for sodium/magnesium-ion batteries

Due to the rapid evolution of the global electronic product industry, the limited availability of lithium resources has prompted extensive research into alternative metal ion batteries that can substitute for lithium batteries. The exceptional potentiality for MXenes as electrode materials in energy storage batteries is demonstrated by excellent conductivity, expansive surface area, and mechanical strength. The performance of Na and Mg on Mo2C and Mo2CO2 monolayers have been investigated employing first-principles calculations, including geometry configurations, electronic structures, ion diffusion properties, open-circuit voltages, and theoretical specific capacities. The conductivity of stable anodes is superior both before and after ion adsorption. Additionally, the formation energies of Na/Mg on the monolayer are negative, indicating a strong binding between metal atoms and the substrate. The migration energy barriers of Na and Mg on Mo2C are estimated to be 0.017 eV and 0.070 eV, respectively, suggesting a significant level of mobility and reversibility for Mo2C. The predicted range of average open-circuit voltages for Na/Mg-ion battery anodes is approximately 0.05–1.00 V in the case of Mo2C and Mo2CO2. The highest concentrations of Na and Mg atoms on Mo2C and Mo2CO2 are achieved through multilayer adsorption up to Mo2CNa3.3, Mo2CMg2, Mo2CO2Na3.3, and Mo2CO2Mg1.8, resulting in corresponding theoretical capacities of 438, 526, 379 and 411 mA·h/g, respectively. In conclusion, the outstanding electrochemical performance of Mo2C and Mo2CO2 anode materials in sodium-ion batteries (SIBs) and magnesium-ion batteries (MIBs) has prompted the exploration of other MXenes electrodes with advantageous characteristics for ion battery applications, contributing to the advancement of renewable energy technology.