A theoretical investigation on the two-dimensional Fe/Mn tricarbides (XC3) as promising electrode materials for lithium-ion batteries

Abstract

2D materials have shown great potential for application in metal-ion batteries due to their promising ionic and electronic conductivity as well as large capacities. In this work, we explore transition metal tricarbides as electrode material to lithium-ion batteries (LIBs) by employing CALYPSO method to conduct a structure search and then perform the first-principles density functional theory (DFT) calculation to study their electronic structure, thermodynamic stability, lithium capacity, lithium diffusion barrier and open circuit voltage. A series of two-dimensional transition metal tricarbides XC3 (X = Fe, Mn) monolayer was obtained from the structure search and four of them (marked by m-XC3 and d-XC3, X = Fe, Mn) were found to possess good dynamical, mechanical and thermodynamic stability from DFT calculation. Further calculation of electronic structure revealed a metallic character for the m-XC3 and d-XC3 (X = Fe, Mn), which ensures good electronic conductivity as electrodes of LIBs. The predicted migration energy barriers of Li diffusion on d-FeC3, d-MnC3, m-FeC3 and m-MnC3 were 0.16 eV, 0.16 eV, 0.19 eV and 0.17 eV respectively, which ensures fast charging/discharging rate. Moreover, d-FeC3, d-MnC3, m-FeC3 and m-MnC3 monolayer were found to have low open-circuit voltage of 1.511 V, 1.423 V, 0.913 V and 0.728 V, which make them suitable for the anode material in LIBs. Finally, the FeC3 and MnC3 monolayer showed theoretical specific capacity of 874 mAhg−1 and 885 mAhg−1. The predicted superior performance of Li storage and transport make the XC3 (X = Fe, Mn) monolayers to be promising candidates as the anode material of LIBs.