论文总字数：23488字

摘 要

采用固态电解质替换锂离子电池中的有机电解液开发全固态锂离子电池，有利于大幅度提高传统锂二次电池的能量密度和安全性能。本课题的主要研究内容是利用固相法制备了石榴石型固态电解质Li₇La₃Zr₂O₁₂（LLZO），然后在LLZO体系的基础上进行Ce、Sm、Gd、Nd、Nb元素掺杂，从而达到提高电解质的电导率的效果。采用XRD以及SEM对电解质的物相组成和微观形貌进行研究和表征，结果表明样品均为立方相结构。采用电化学阻抗谱对电解质的电化学性能进行了表征，实验结果表明，进行Nb和Sm共同掺杂的体系效果最好，电导率在室温下达到8.12×10^-4S·cm^-1，采用直流恒压极化曲线得到其电子电导率为3.75×10^-9 S·cm^-1，并且由阿伦尼乌斯曲线得到其活化能为0.41eV。

关键词：锂离子电池 固态电解质 石榴石结构 锆酸镧锂 离子电导率

Effects of Lanthanide Doping on the Structure and Properties

of Garnet-type Solid Electrolyte

Abstract

Replacing organic electrolytes in lithium-ion batteries with solid-state electrolytes to develop all-solid-state lithium-ion batteries is beneficial to greatly increasing the energy density and security. The main research content of this subject is to prepare garnet-type solid electrolyte Li₇La₃Zr₂O₁₂ (LLZO) by solid-state reaction method, and then doping Ce, Sm, Gd, Nd and Nb elements on the basis of LLZO system to improve the conductivity of electrolyte. The phase composition and morphology of the electrolyte were studied and characterized by XRD and SEM. The results showed that the samples were cubic phase. The electrochemical properties of the electrolyte were characterized by electrochemical impedance spectroscopy. The experimental results show that the system with Nb and Sm co-doping has the best effect, and the conductivity reaches 1.06×10^-3S·cm^-1 at room temperature. The electron conductivity of the constant voltage polarization curve was 3.75×10^-9 S·cm^-1, and the activation energy was 0.41 eV from the Arrhenius curve.

Key Words: Lithium ion batteries; Solid electrolyte; Garnet-type; Lithium lanthanum zirconium oxide; Ionic conductivity

目 录

摘要………………………………………………………………………….……………………I

ABSTRACT……………………………………………………………………………………II

第一章 文献综述…………………………………………………………………………1

1.1引言…………………………………………………..……………………………………1

1.2 全固态锂离子电池……………………………………………………………1

1.3 固态电解质……………………………………………………………………………2

1.3.1 固态电解质的概述……………………………………………………………2

1.3.2 固态电解质的分类……………………………………………………………2

1.3.3 石榴石型固态电解质……………………………………………………………2

1.4 LLZO固态电解质的晶体结构…………………………………………………………3

1.5 LLZO固态电解质的合成方法……………………………………..……………………3

1.5.1高温固相反应法……………………………………………………………….4

1.5.2 溶胶-凝胶法……………………………………………………………………….4

1.5.3 场辅助烧结法……………………………………………………………………..5

1.5.4 其他制备方法……………………………………………………………………..5

1.6 LLZO的掺杂改性研究…………………………………………………………………..5

1.6.1 LLZO的离子电导率………………………………………………………………5

1.6.2 Zr位掺杂改性……………………………………………………………………...6

1.7 研究目的和内容………………………………………………………………………….6

1.7.1 研究目的…………………………………………………………………………..7

1.7.2 研究内容…………………………………………………………………………..7

第二章 实验及表征……………..……………………………………………………………8

2.1实验原料与实验仪器……………………………………………………………………8

2.1.1 实验原料…………………………………………………………………………..8

2.1.2 实验仪器…………………………………………………………………………..8

2.2实验方法…………………………………………………………………………………9

2.3 表征方法……………………………………………...…………………………………11

2.3.1 X射线衍射分析…………………………………………………………………..11

2.3.2 扫描电子显微镜分析…………………………………………………………….11

2.3.3 密度与气孔率分析……………………………………………………………….11

2.3.4 电导性能表征……………………………………………………………………12

第三章 结果与讨论…………………………………………………………………14

3.1 引言……………………………………………………………………..………………14

3.2 La系元素掺杂对LLZO固态电解质密度的影响…………...…………………………14

3.3 La系元素掺杂对LLZO固态电解质气孔率的影响…………………………………...16

3.4 La系元素掺杂对LLZO固态电解质微观形貌的影响………………………………...17

3.5 La系元素掺杂对LLZO固态电解质物相分析的影响………………………………...17

3.6 La系元素掺杂对LLZO固态电解质电化学性能的影响……………………………...19

3.6.1 离子电导率……………………………..………………………………………..19

3.6.2 阿伦尼乌斯激活能………………………………………………………………23

3.6.3 电子电导率………………………………………………………………………25

第四章 结论与展望………………………………………………………………………26

4.1 结论…………………………………………………………………………..………….26

4.2 展望……………………………………………………………………………………...26

参考文献………………………………………………………………………………….……27

致谢…………………………………………………………………………………………...30

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