【作者】 侯柱锋；

【导师】 朱梓忠；

【作者基本信息】 厦门大学 ， 凝聚态物理， 2004， 博士

【摘要】 锂离子电池与传统的二次电池相比保持了电压高、能量密度大、重量轻，又具有安全性能好、自放电小等优点，使之在便携电子设备以及电动汽车等方面有广阔的应用前景。开发锂离子电池的关键之一就是寻找合适的电极材料，使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。在应用中，大多以石墨和各种碳材料作为负极材料，但是碳负极材料存在一些自身的缺点。为了寻找性能更高的负极材料，许多新型的锂离子负极材料特别是金属间化合物在近来的锂离子电池研究中引起了相当的重视。 尽管近年来采用第一性原理对锂离子电极材料的理论研究取得了一些成功，但是大多集中于正极材料，对锂离子电池负极材料的理论研究并不多见。为此，我们采用第一性原理对目前一些新型的负极材料金属间化合物的锂嵌入性质进行了理论研究，重点研究了负极材料在首次充放电过程中锂嵌入负极材料时的锂嵌入形成能，以及锂的嵌入对负极材料体积和电子结构的影响。并与已有的实验结果进行比较，以期为锂离子电池负极材料的研究提供了一些有意义的理论指导。 本论文可分为两部分。第一部分介绍了研究工作所涉及的基本理论和第一原理方法。首先介绍了密度泛函理论，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(局域密度近似和广泛梯度近似)等。接着介绍了本研究工作中所采用的具体的电子结构计算方法，即平面波或混合基矢展开的第一性原理赝势法。并对基于平面波赝势法的VASP程序包的特点作了介绍。此外，还介绍了锂离子电池的工作原理，中文摘要以及常见的铿离子电池电极材料的特性。介绍了采用第一性原理对铿离子电池电极材料进行理论研究的计算模型，并给出了在对铿离子负极材料的铿嵌入性质进行从头计算时所作的一些近似和所定义的物理量。 第二部分分为四章，分别给出T对MSb(M为AI，Ga和In)，Cusn，MgZSn，Snsb的Li嵌入性质的从头计算结果、对MgZSn和LiZMgsn的几何和电子结构所进行的研究结果，以及对黄铁矿CuXZ(x=S，Se和Te)的电子结构所进行的系统的从头计算。在第四章中，使用混合基表示的第一原理厦势法，研究了AISb、Gasb和Insb在Li嵌入时的形成能以及相应的电子结构，还给出了Li嵌入时主体材料的体积变化，能带结构、电子态密度以及电荷密度分布等性质，并讨论了AISb、Gasb和Insb作为负极材料的特点，计算表明Li嵌入AISb、Gasb和Insb时的嵌入形成能都在2.0 eV附近，由于Li的嵌入导致AISb、Gasb和工nsb的体积膨胀比较大，表明每单位原胞AISb、Gasb和工nsb的最大铿嵌入量较小，在0.25个铿原子左右。在第五章中，使用混合基和平面波表示的第一原理鹰势法，分别研究了闪锌矿结构Cusn、反CaFZ结构MgZSn和NaCI结构Snsb在Li嵌入时的形成能以及相应的电子结构，给出了Li嵌入时主体材料的体积变化，能带结构、电子态密度以及电荷密度分布等性质，分别讨论了闪锌矿结构Cusn、反CaFZ结构MgZSn和NaCI结构Snsb作为铿离子电池负极材料的特点，计算表明Li嵌入闪锌矿结构Cusn时的嵌入形成能大致在3.seV附近，铿嵌入反CaFZ结构MgZSn的间隙位置时平均每个铿原子的形成都大致在2.ZeV，铿嵌入Snsb的间隙位置时平均每个铿原子的形成大致在2.7eV。在第六章中，使用第一性原理的平面波鹰势法，计算了MgZsn在多种结构下的“结构一能量”相图、各种结构的晶格常数、结合能等，计算表明M歇sn的次稳态相为c23一PbC12结构，并讨论了其电子结构。另外，还计算比较了LiZMgsn在两种不同结构时的结合能以及电子结构，得到LiZMgsn在LiZMgsi结构(空间群为厦门大学博士学位论文尸聪m，No.215)时相对更稳定。在第七章中，使用第一性原理的平面波质势法，系统地研究了铜黄铁矿的CuSZ、CuseZ和CuTeZ，计算表明这三种铜黄铁矿化合物是良导体，费米能级处的导电电子主要来自硫素原子的p电子和铜原子的d电子，前者占优势。 本文应用第一性原理方法系统地计算了Li嵌入到一系列新型铿离子电池负极材料金属间化合物时的嵌入形成能、体积膨胀以及电子结构等嵌入性质，说明采用第一性原理方法研究铿离子电池负极材料确实可行，与实验相比简便，更能从微观的电子结构上来了解铿离子负极材料的电化学性能。这也是第一性原理在研究铿离子电池电极材料中得以广泛应用的原因。使用第一性原理方法，只需从铿离子电池负极材料的结构等基本物理性质从发，就可以讨论和预测铿离子电池负极材料在首次充电过程中的电化学性能，这样就可以在原子尺度上快速方便地搜寻和设计性能优越的铿离子电池负极材料，大大减少设计在实验上探索高性能铿离子负极材料的盲目性以及所需的各种资源。更多还原

【Abstract】 In comparison with the conventional secondary batteries, such as nick-metal hydride, nickel-cadmium or lead-acid, lithium-ion batteries (LIBs) have many outstanding features: high voltages, high energy densities (both volumetric and gravimetric energy densities), low self-discharge rate, no memory effect, wide temperature range of operation, excellent cycle life and safety characteristics. These outstanding properties make LIBs be the current rechargeable power source of choice for portable electrics devices and electric vehicles. In the development of LIBs the key step is to look 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. In commercial applications the graphite and other carbonaceous materials were widely used as negative electrode materials, however, these carbon-based anode materials have some self-blemish. To get better anode materials, a large number of alternative possibilities for anodes of LIBs have recently been studied and reported in the literatures. Especially, the intermetallic compounds have attracted special attentions in the research of anode materials for LIBs.First principles calculations have been successfully used to identify the cathode materials for lithium ion batteries. However, there are less theoretical studies on the anode materials. We therefore apply the model of theoretical studies on cathode to anode materials. We perform first-principles calculations to investigate the lithium intercalations in anode materials such as intermetallic compounds, in order to provide some theoretical guides for the experimental studies of anode materials.This thesis consists of two parts. In the first part we present the basic theories employed in this study and the first-principles methods used for the present calculations. We firstly introduce the density function theory (DFT), which includes major ideas of DFT, Hobenberg-Kohn theorem, Kohn-Sham equations, and the approximations for exchange andcorrelations (the local density approximation and the generalized gradient approximation). We then describe the details of computational methods used in our work, i.e. the ab initio pseudopotential methods with the plane wave and mixed basis expansion of wavefunctions. We also present the major characters of the Vienna ab initio Simulation Package (VASP): a total-energy plane wave code. In addition, the principles of lithium ion batteries and the characteristics of cathode and anode materials were also introduced. We also described the models of first-principles calculations on the electrode materials and presented the approximations and concepts used in these models.In the second part, the ab initio pseudopotential method has been employed to investigate the lithium intercalations in intermetallic compounds anode materials such as MSb (M = Al, Ga, and In), CuSn, MgSn and SnSb, the geometrical structures and electronic properties of Mg2n and Li2MgSn, and the electronic structures of CuS2, CuSe2 and CuTe2. In the fourth chapter, the lithium intercalations in AlSb, GaSb and InSb have been studied by using the mixed basis ab initio norm-conserving pseudopotential method. The formation energies, changes of volumes, electronic structures and charge densities of lithium intercalations in zinc blende-type antimonides Li,MSb (M = Al, Ga, and In) are presented. Our calculations show that during lithium insertions in MSb the lithium intercalation formation energies per lithium atom are all around 2.0 eV. The volume expansions of AlSb, GaSb and InSb due to lithium insertions are relatively large, which might imply that the limit of Li intercalation in antimonides should be small. In the fifth chapter, the pseudopotential methods with mixed-basis and plane waves have been employed to investigate the non-carbon-baring anode materials, such as CuSn with zinc-blende structure, Mg2Sn with anti-CaF2 structure and SnSb wi更多还原