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首页> 外文学位 >Structure and properties of garnet-type lithium ion conductors Li7-xLa3Zr2-xTaxO12 and their applicability in lithium-ion batteries.
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Structure and properties of garnet-type lithium ion conductors Li7-xLa3Zr2-xTaxO12 and their applicability in lithium-ion batteries.

机译：石榴石型锂离子导体Li7-xLa3Zr2-xTaxO12的结构和性能及其在锂离子电池中的应用。

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摘要

Li-ion batteries have served as the primary energy storage units in portable electronic devices and will continue to play an important role in the sustainable energy future. Despite decades of developments, the energy density and safety of Li-ion batteries still cannot live up to the increasing demands of modern society. Many issues are related to the state-of-art liquid electrolyte due to its intrinsic volatility and flammability. Solid-state lithium ionic conductors have received much attention recently and the garnet-type lithium ion conductors have emerged as the most promising candidate in the oxide system owing to their high conductivity and good chemical/thermal stability. This dissertation describes my PhD research work on the structure and properties of the garnet materials and their applicability in lithium-ion batteries.;In Chapter 3, a series of garnet compounds Li7-xLa3Zr 2-xTaxO12 (LLZTx, x= 0 -- 2) were synthesized and their phases and transport properties were characterized. The highest bulk conductivity of 9.6 x 10-4 S/cm is achieved for the composition Li6.7La3Zr1.7Ta 0.3O12 which marks the highest value reported in the literature at the time of publication. Ta5+ doping stabilizes the cubic garnet structure and the cation Ta5+ and Zr4+ form complete solid solutions for the cubic garnet compounds. A carefully conducted study of the LLZTx series reveals that pure cubic garnet phase forms only when x ≥ 0.6.;To understand the transport properties of the LLZTx series, the structures of selected compositions in this series were studied by diffraction techniques and computer simulation. Neutron diffraction study provided information about the average structure whereas the pair distribution function (PDF) analysis shed light on the local structure. Atomistic simulation based on interatomic potentials was carried out and a statistical approach was employed to extract useful structural information. We found that both tetrahedral and octahedral Li display strong position disorders as visualized via nuclear density maps. The first-neighbor Li-Li interactions strongly influence the lithium distribution. PDF analysis and computer simulation results indicate that mobile Li ions hop through the tetrahedral-octahedral shared faces.;Finally, the applicability of the LLZTx compounds in lithium-ion batteries was evaluated. It was found that the LLZTx compounds were stable against Li metal but unstable against moisture and CO2. The composition LLZT0.3 is more compatible with the cathode material LiCO2 than the LiFePO 4. Partial success was achieved using sol-gel method. The pulsed electric current sintering was successfully applied to the densification of LLZT0.6 powder.
机译：锂离子电池已成为便携式电子设备中的主要储能单元，并将继续在可持续能源的未来中发挥重要作用。尽管有数十年的发展，但锂离子电池的能量密度和安全性仍不能满足现代社会日益增长的需求。由于其固有的挥发性和易燃性，许多问题与最新的液态电解质有关。固态锂离子导体近来备受关注，并且石榴石型锂离子导体由于其高电导率和良好的化学/热稳定性而成为氧化物系统中最有希望的候选者。本论文描述了我对石榴石材料的结构和性能及其在锂离子电池中的适用性的博士学位研究;第三章，一系列石榴石化合物Li7-xLa3Zr 2-xTaxO12（LLZTx，x = 0-2进行了合成，并对其相和传输性质进行了表征。 Li6.7La3Zr1.7Ta 0.3O12组合物的最高体积电导率为9.6 x 10-4 S / cm，这是文献出版时报道的最高值。 Ta5 +掺杂稳定了立方石榴石的结构，阳离子Ta5 +和Zr4 +形成了立方石榴石化合物的完整固溶体。对LLZTx系列进行的仔细研究表明，只有当x≥0.6时，才会形成纯立方石榴石相；为了了解LLZTx系列的传输性能，通过衍射技术和计算机模拟研究了该系列中选定成分的结构。中子衍射研究提供了有关平均结构的信息，而对分布函数（PDF）分析则为局部结构提供了信息。进行了基于原子间电势的原子模拟，并采用了统计方法来提取有用的结构信息。我们发现，通过核密度图可视化，四面体和八面体Li均显示出强位错。第一邻居Li-Li相互作用强烈影响锂的分布。 PDF分析和计算机仿真结果表明，可移动锂离子跳跃通过四面体-八面体共享面。最后，评估了LLZTx化合物在锂离子电池中的适用性。发现该LLZTx化合物对锂金属稳定，但对水分和CO 2不稳定。组合物LLZT0.3比LiFePO 4与正极材料LiCO 2相容性更高。使用溶胶-凝胶法获得了部分成功。脉冲电流烧结成功应用于LLZT0.6粉末的致密化。

著录项

  • 作者

    Wang, Yuxing.;

  • 作者单位

    Michigan State University.;

  • 授予单位 Michigan State University.;
  • 学科 Materials science.
  • 学位 Ph.D.
  • 年度 2014
  • 页码 160 p.
  • 总页数 160
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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