论文总字数：26448字

摘 要

近来，由于新能源供能科技的飞速发展和新时代友好环境建设的需求，高容量、大电流、长循环寿命、安全无环境污染的新型高效Li离子电池得到了广泛的关注。阳离子无序富锂材料Li_2.4FeTi_0.9O₄因其较高的理论容量，三维Li离子扩散通道，Li过量使Li离子能快速扩散等优势而具有成为新型高性能Li离子电池正极材料的潜力。但近年来研究表明，Li_2.4FeTi_0.9O₄材料在大电流、长循环工作条件下，由于其中氧的流失产生了不可逆容量，造成其循环稳定性较差。本文针对Li_2.4FeTi_0.9O₄材料的缺陷，通过氟掺杂对材料微观结构进行调控，以此来抑制充电过程氧的损失，从而优化其电化学性能。

本文拟通过溶胶-凝胶法合成Li_2.4FeTi_0.9O₄材料的前驱体，并通过高温固相反应完成具有阳离子无序岩石结构的Li_2.4FeTi_0.9O₄材料的制备。通过使用LiF对其进行氟掺杂，为研究氟掺杂量与电池性能的变化关系，采用球磨烧结等合成工艺完成不同掺杂量的Li_2.4FeTi_0.9O_4-xF_x电极的制备，制作出多组对比材料，采用X-射线衍射（XRD），扫描电子显微镜（SEM）等方法表征材料的微观结构，采用充放电循环测试、循环伏安测试等手段对材料的电化学性能进行测试，比较不同量的氟掺杂条件下不同实验样品的性能。

通过对前人的研究，对实验结果做了如下预测：

1、氟掺杂对材料的形貌特征没有明显的影响，由此可预测，经过不同量氟掺杂的Li_2.4FeTi_0.9O_4-xF_x材料的微观形貌表征，与Li_2.4FeTi_0.9O₄的微观形貌变化不明显，粒径尺寸均为纳米级。

2、氟掺杂不会改变无序材料的电化学反应基本反应历程，一定程度上抑制了氧的氧化还原反应，材料中阴离子的平均价态降低，会有利于过渡金属发生氧化还原反应，由此可预测，氟掺杂可以提高Li_2.4FeTi_0.9O₄材料的比容量和循环稳定性。

3、氟掺杂的过程中，渗入晶格内部，因此材料结构稳定性得到优化。由此可以预测，对于Li_2.4FeTi_0.9O₄材料，氟掺杂可以一定程度上改善材料电导性，降低材料内部电阻。

关键词：锂离子电池 阳离子无序富锂正极材料 氟掺杂 电化学性能

Study on Fluorine Doping and Lithium Storage Performance of Cation-Disordered Lithium-Excess Oxide Electrode Materials

Abstract

Recently, due to the rapid development of new energy supply technology and the need for a new era of friendly environment construction, new high-efficiency Li-ion batteries with high capacity, large current, long cycle life, safety and no environmental pollution have received widespread attention. The cationic disordered lithium-rich material Li_2.4FeTi_0.9O₄ has the potential to become a new type of high-performance Li-ion battery cathode material due to its high theoretical capacity, three-dimensional Li ion diffusion channels, and excessive Li to rapidly diffuse Li ions. However, in recent years, studies have shown that Li_2.4FeTi_0.9O₄ material under high current, long cycle working conditions, due to the loss of oxygen produced irreversible capacity, resulting in poor cycle stability. In this paper, the defects of Li_2.4FeTi_0.9O₄ material are controlled by fluorine doping to control the microstructure of the material to suppress the loss of oxygen during the charging process, thereby optimizing its electrochemical performance.

This paper intends to synthesize the precursor of Li_2.4FeTi_0.9O₄ material by sol-gel method, and complete the preparation of Li_2.4FeTi_0.9O₄ material with cationic disordered rock structure by high temperature solid phase reaction. By doping it with LiF, in order to study the relationship between the amount of fluorine doping and the performance of the battery, the synthesis of Li_2.4FeTi_0.9O_4-xF_x electrodes with different doping amounts was completed by using a ball milling and sintering synthesis process, and many groups were produced Contrast materials, using X-ray diffraction (XRD), scanning electron microscope (SEM) and other methods to characterize the microstructure of the material, using charge and discharge cycle test, cyclic voltammetry test and other means to test the electrochemical performance of the material, compare different amounts The performance of different experimental samples under fluorine doping conditions.

Through the research of the predecessors, the experimental results are predicted as follows:

1. Fluorine doping has no obvious effect on the morphological characteristics of the material. It can be predicted that the microscopic morphology of Li_2.4FeTi_0.9O_4-xF_x material doped with different amounts of fluorine is different from that of Li_2.4FeTi_0.9O₄. The shape change is not obvious, and the particle size is all in the nanometer range.

2. Fluorine doping will not change the basic reaction process of the electrochemical reaction of disordered materials, to a certain extent, it inhibits the redox reaction of oxygen, and the average valence state of the anions in the material is reduced, which will facilitate the redox reaction of transition metals. It is predicted that fluorine doping can improve the specific capacity and cycle stability of Li_2.4FeTi_0.9O₄ material.

3. In the process of fluorine doping, it penetrates into the lattice, so the structural stability of the material is optimized. It can be predicted from this that for Li_2.4FeTi_0.9O₄ material, fluorine doping can improve the electrical conductivity of the material to a certain extent and reduce the internal resistance of the material.

Keywords: Lithium-ion battery, Cation-disordered lithium-excess cathode materials, Fluorine doping, Electrochemical performance

目 录

摘要 2

Abstract 3

第一章 绪论 6

1.1 引言 6

1.2 锂离子电池的工作原理 6

1.3 几种经典的锂离子电池正极材料 7

1.3.1 层状结构正极材料-LiCoO₂ 7

1.3.2 尖晶石结构正极材料-LiMn₂O₄ 8

1.3.3橄榄石结构正极材料-LiFePO₄ 9

1.4 阳离子无序的岩石型正极材料 9

1.4.1阳离子无序的岩石型材料的结构 9

1.4.2阳离子无序的岩石型正极材料存在的问题 10

1.5 课题意义及内容 11

第二章 实验内容及方法 12

2.1所需仪器和药品 12

2.1.1仪器 12

2.1.2 药品 13

2.2 实验样品制备 13

2.2.1 Li_2.4FeTi_0.9O₄材料的制备 13

2.2.2 Li_2.4FeTi_0.9O_4-xF_x材料的制备 14

2.3 微观结构表征 15

2.3.1 XRD射线衍射分析 15

2.3.2 材料微观形貌分析 15

2.4 电化学测试技术 15

2.4.1 电极制备及电池组装 15

2.4.2 电极材料充放电测试 16

2.4.3 电极材料循环伏安测试 16

2.4.4 电极材料电化学阻抗谱测试 16

第三章 实验结果预测与讨论 17

3.1 SEM分析 17

3.2 XRD分析 18

3.3 电化学性能测试 19

3.3.1 循环伏安分析 19

3.3.2 充放电特性和循环稳定性能 20

请支付后下载全文，论文总字数：26448字