(1. 湘潭大学 材料设计及制备技术湖南省重点实验室，湘潭 411105； 2. 湘潭大学 材料科学与工程学院，湘潭 411105； 3. 中南大学 冶金与环境学院，长沙 410083)
摘 要: 采用基于密度泛函理论的第一性原理计算Li嵌入VSi2的各种可能反应的嵌Li形成能、理论比容量和体积膨胀率，从热力学上证实VSi2可以与Li反应，并得到最有可能的反应路径为：Li嵌入VSi2中首先生成V5Si3和Li13Si4；然后Li13Si4与Li反应形成Li21Si5；V5Si3不再与Li反应；最终态为V5Si3和Li21Si5。通过对嵌Li路径的分析，得到Li-Si-V三元系0K相图。进一步计算VSi2和V5Si3的电子结构和弹性性质，发现嵌Li前后硅化物的导电性质没有改变，但嵌Li产物V5Si3的导电性和延展性优于基体VSi2。计算结果表明：VSi2在嵌Li过程中生成的V5Si3，可以作为缓解体积膨胀的缓冲相和具有更好导电性能的导电剂，从而提高其脱嵌Li的循环性能。
关键字: 第一性原理；VSi2；嵌锂性质；相图；电子结构；弹性性质
（1. Key Laboratory of Materials Design and Preparation Technology of Hunan Province, Xiangtan University, Xiangtan 411105, China; 2. School of Materials Science and Engineering, Xiangtan University, Xiangtan 411105, China; 3. School of Metallurgy and Environment, Central South University, Changsha 410083, China）
Abstract:First-principles calculation based on the density functional theory was employed to calculate the Li-insertion formation energy, specific capacity and volume expansion rate of every possible reactions of Li intercalation into VSi2. VSi2 can react with Li, and the most possible reaction pathway of Li intercalation into VSi2 is found. Firstly, Li reacts with VSi2 to form Li13Si4 and V5Si3, then Li reacts with Li13Si4 to produce Li21Si5, while V5Si3 cannot react with Li. So, the final reactants are V5Si3 and Li21Si5. The 0K phase diagram of Li-Si-V ternary system can be determined by analyzing the reaction pathway of Li intercalation into VSi2. The electronic structure and elastic properties of VSi2 and V5Si3 were calculated further. The results show that both VSi2 and V5Si3 are characterized with a metallic conductor, but the conductivity and ductility of V5Si3, production after Li-insertion, are better than those of VSi2 substrate. The results of calculation predict that V5Si3 can act as a buffer phase to release the mechanical stress due to volume change during cycling of the electrode and a conductive agent to provide better conductivity, while improve the cycle performance of lithium intercalation/extraction.
Key words: first-principles; VSi2; Li-insertion properties; phase diagram; electronic structure; elastic properties
