中文摘要：

MXenes是一类新型的二维金属碳化物或碳氮化物.本文使用密度泛函理论,分别研究了其中Ti2C、Nb2C和V2C的结构与储锂性能,以及表面氟（F）官能团对其结构和储锂性能的影响.吸附能、态密度和电荷布居的计算结果表明：该二维晶体表面可以吸附双层锂原子.Ti2C、V2C和Nb2C最高储Li的理论比容量分别为995.04、941.31、541.93 mAh·g（-1）.此外,F官能团可以有效提高这三种二维晶体锂化结构的稳定性与导电性。

英文摘要：

MXenes are a new series of two-dimensional （2D） carbides or nitrides. Lithium storage properties and lithiated structures of three MXenes phases, Ti2C, V2C, and Nb2C, are studied by density functional theory. Additionally, the influence of fluorine functional groups on the lithiated structures and properties are also investigated. By calculating the adsorption energy, density of state, and charge population, we observe that double Li atom layers can be adsorbed on the surfaces of MXenes. For Ti2C, V2C, and Nb2C, the calculated maximum Li capacities reach values up to 995.04, 941.31, and 541.93 mAh·g-1, respectively. Fluorine functional groups are observed to effectively enhance the stability and conductivity of the lithiated structures of these three 2D crystals.