(1. 湘潭大學(xué) 材料設(shè)計(jì)及制備技術(shù)湖南省重點(diǎn)實(shí)驗(yàn)室，湘潭 411105； 2. 湘潭大學(xué) 材料科學(xué)與工程學(xué)院，湘潭 411105； 3. 中南大學(xué) 冶金與環(huán)境學(xué)院，長沙 410083)
摘 要: 采用基于密度泛函理論的第一性原理計(jì)算Li嵌入VSi2的各種可能反應(yīng)的嵌Li形成能、理論比容量和體積膨脹率，從熱力學(xué)上證實(shí)VSi2可以與Li反應(yīng)，并得到最有可能的反應(yīng)路徑為：Li嵌入VSi2中首先生成V5Si3和Li13Si4；然后Li13Si4與Li反應(yīng)形成Li21Si5；V5Si3不再與Li反應(yīng)；最終態(tài)為V5Si3和Li21Si5。通過對(duì)嵌Li路徑的分析，得到Li-Si-V三元系0K相圖。進(jìn)一步計(jì)算VSi2和V5Si3的電子結(jié)構(gòu)和彈性性質(zhì)，發(fā)現(xiàn)嵌Li前后硅化物的導(dǎo)電性質(zhì)沒有改變，但嵌Li產(chǎn)物V5Si3的導(dǎo)電性和延展性優(yōu)于基體VSi2。計(jì)算結(jié)果表明：VSi2在嵌Li過程中生成的V5Si3，可以作為緩解體積膨脹的緩沖相和具有更好導(dǎo)電性能的導(dǎo)電劑，從而提高其脫嵌Li的循環(huán)性能。
關(guān)鍵字: 第一性原理；VSi2；嵌鋰性質(zhì)；相圖；電子結(jié)構(gòu)；彈性性質(zhì)
（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
