【作者】 蔡娜丽；

【导师】 朱梓忠；

【作者基本信息】 厦门大学 ， 凝聚态物理， 2006， 硕士

【摘要】 锂离子电池由于具有高电压、高能量密度、自放电小、循环寿命长、无污染和无记忆效应等优点,已广泛应用于移动电话、笔记本电脑、小型摄像机等电器设备上,在电动汽车、航天航空、卫星、空间军事等领域也显示出了良好的应用前景。但是目前锂离子电池的性能仍有很大的提高空间。关健在于寻找合适的电极材料,使得锂离子电池具有足够高的储锂量和很好的锂脱嵌可逆性,以保证电池的高电压、大容量和长循环寿命的要求。目前商业化的锂离子电池的负极材料主要是石墨和其它各种碳材料,但由于碳负极材料存在一些自身的缺点,因此寻找性能更高的负极材料成为锂离子电池研究的重要方面,许多新型的负极材料特别是过渡金属氮化物尤其受到关注。我们采用第一原理的从头计算方法,对氮化锂及其衍生物锂的过渡金属氮化物Li2.5Cu0.5N的电子结构和几何结构进行了理论计算和分析,对Li2.5Cu0.5N作为锂离子电池负极材料的锂脱嵌性质进行了计算,对锂从此材料中脱出所导致的电子结构的变化和几何结构的变化提供了比较完整的基本理论数据,以期为此类负极材料的进一步的研究提供理论指导。本论文可分为两部分。第一部分包括第一章和第二章,第一章介绍了锂离子电池的工作原理,及其主要材料的性质和特点。第二章介绍了研究工作所涉及的基本理论和方法,包括密度泛函理论的基本思想、Hobenberg- Kohn定理、Kohn-Sham方程和交换关联近似(包括局域密度近似和广泛梯度近似)等。也介绍了本研究工作中所采用的具体的电子结构计算方法,即基于平面波展开的第一性原理赝势法。并对本研究工作所采用的计算工具VASP程序包进行简要的介绍。第二部分包括第三章和第四章,分别对Li3N的几何结构和电子结构、Li3N的脱锂结构稳定性、Li2.5Cu0.5N的电子结构和几何结构、Li2.5Cu0.5N的脱锂性质进行理论计算和分析。第三章计算了氮化锂在D61 h、DO3、A15、DO19、L12这五种可能结构下的能量-体积相图,对这几种结构下的氮化锂脱去一定量的锂后所得到的材料的能量-体积相图也进行了计算。结果表明,对于Li3N完整晶体, D61h更多还原

【Abstract】 High voltages, high energy densities, low self-discharge rate, no memory effect, wide temperature range of operation, excellent cycle life and safety characteristics, so many outstanding features have made lithium ion secondary batteries widely used in cell phone, notebook PC, miniature vidicon etc. The lithium ion batteries also show good application prospect in electric vehicles, space flight, and spatial military. However, the present performances of lithium ion batteries still need to be improved. The key step is to seek for more suitable electrode materials, which should store enough lithium and have excellent reversibility of lithium intercalation/extraction in order to fulfill the cell performance of high voltage, high energy density and excellent cycle life. The commercial anodes are usually graphite and other carbonic materials. But due to the disadvantage of carbon based materials, better anode materials are eager to be found. A large number of alternative possibilities for anode materials have recently been studied and reported. Especially, the lithium ternary transition metal nitrides have attracted special attentions.In the present thesis, the first-principles calculations have been used to study the atomic structures, electronic properties and Li deintercalations in Li3N and in Li2.5Cu0.5N. Our study could provide some theoretical guides for the experimental studies on this anode material.The thesis consists of two parts. The first part consists of Chapter 1 and 2. In Chapter 1 the working principles of lithium ion batteries and the characteristics of primary electrode materials are introduced. In Chapter 2 the basic theories employed in this study and the first-principles methods used for the present calculations are described, including major ideas of density functional theory, the Hohenberg-Kohn theorem, the Kohn-Sham equation and the approximations for exchange and correlations (the local density approximation and the generalized gradient approximation). We also describe some details of the computational method, i.e. the ab initio pseudopotential method with the plane wave expansion. The major characters of the Vienna ab initio Simulation Package (VASP) which is used in our calculations are presented as well.In the second part (including Chapter 3 and 4) the atomic structures and electronic更多还原