二维钼基双过渡金属碳化物作为锂离子电池阳极材料的电化学性能研究

As a new type of two-dimensional (2D) material, two-dimensional Mo-based double transition metal carbide or nitride (MXenes) has received extensive attentions because of its simple preparation process, flexible and controllable physical and chemical properties, and high structural stability. However, most studies have focused on the performance of mono-transition metal MXenes. The effect of double transition metal combinations and its surface modifications on electrochemical performances of MXenes have not been systematically reported. Therefore, in this study, the first-principles calculation method based on density functional theory was used to systematically evaluate the electrochemical performance of 35 Mo-based ordered double transition metal MXenes, including intrinsic structures Mo₂MC₂ (M=Sc, Ti, V, Zr, Nb, Hf, Ta) and the corresponding four types of surface functionalized structures Mo₂MC₂T₂ (T=H, O, F, OH). The calculation results show that different modification groups on the surface of the MXenes play a decisive role in both the adsorption of Li atom on the surface and the diffusion ability of lithium atoms. The theoretical capacity is in the range of 121~195mA•h/g, and the ideal OCV (0.5~0.8V) can be obtained by intrinsic and H-modified structures. At the same time, the extremely low ion diffusion barrier (0.03~0.06eV) of the intrinsic structures could greatly improve the charging or discharging rate of lithium ion batteries.