摘要开发高能量密度锂离子电池正极材料，改善其循环稳定性、安全性和极端条件工作性能是动力电池的研究热点之一。

本文利用水热法在220℃、24h合成反尖晶石结构纳米级（50-100nm）正极材料LiCo(VO4)1-X(PO4)X（记为LCV1-XPX）（X=0、0.05、0.1、0.2和0.3），Ｘ射线衍射（XRD）表明取代的(PO4)3-进入了LiCoVO4(记为LCV)晶格内部。扫描电镜（SEM）显示LCV的粒径分布在50～100ｎｍ之间。研究发现，不同(PO4)3-取代量所获得的反尖晶石结构LCV1-XPX中，LCV0.9P0.1首次放电比容量最高，为67.7mAh/g，LCV，LCV0.95P0.05和LCV0.8P0.2首次放电比容量分别为49.8mAh/g，55.7mAh/g和60.1mAh/g；10次循环后，LCV0.9P0.1放电比容量保持率最高，为60.3%，而LCV，LCV0.95P0.05和LCV0.8P0.2放电比容量保持率分别为20%，57.4%和50.7%。通过交流阻抗分析计算得出LiCoVO4的锂离子扩散系数为7.81×10-14cm2/s，LCV0.9P0.1的锂离子扩散系数为3.78×10-13cm2/s，比LCV提高了一个数量级，说明部分(PO4)3-取代有利于提高锂离子扩散系数。同时部分(PO4)3-取代不仅能够改善材料的循环稳定性而且提高了材料的放电电压平台。

毕业论文关键词： 钒酸钴锂；(PO4)3-取代；锂离子扩散系数57354

 Synthesis of LiCo(VO4)1-X(PO4)X by hydrothermal method and its electrochemical properties

Abstract Developing high energy density cathode materials, as well as improving the cycle stability, safty and performance in extreme environment, is one of the research interests for Li-ion batteries.

In this paper, inverse spinel structure nano-size (50-100 nm) LiCo(VO4)1-X(PO4)X (denoted by LCV1-XPX) (X=0、0.05、0.1、0.2 and 0.3) was synthesized by hydrothermal method at 220℃ for 24h. XRD indicates that substitution of (PO4)3- has been into the LiCoVO4 (denoted by LCV) lattice. SEM shows that the diameter of LiCoVO4 distributed from 50 to100nm.Comparing the LCV1-XPX with different content of (PO4)3-, LCV0.9P0.1 has the highest initial discharge specific capacity, 67.7 mAh/g, and LCV, LCV0.95P0.05 and LCV0.8P0.2 initial discharge specific capacity is 49.8mAh/g, 55.7mAh/g and 60.1 mAh/g After 10 cycles, LCV0.9P0.1 discharge specific capacity to maintain the highest rate, 60.3%, and LCV, LCV0.95P0.05 and LCV0.8P0.2 discharge specific capacity retention rate were 20%, 57.4% and 50.7%. Calculated by exchanges impedance analysis, the lithium iondiffusion coefficient of LCV is 7.81×10-14 cm2/s, and compare with LCV the diffusion coefficient of LCV0.9P0.1 lithium ion is 3.78×10-13 cm2/s, It shows that partial (PO4)3- substitution is beneficial to increase the diffusion coefficient of lithium ion. Partial (PO4)3- substitution Not only can improve the cycle stability of the material but the material of the discharge voltage platform..

Key words: LiCoVO4; (PO4)3- substitution; Li+ diffusion coefficient

 目  录

1 绪论 1

1.1 锂离子电池的简介 1

1.2 锂离子电池的发展现状 1

1.3 锂离子电池的结构和工作原理 1

1.4 锂离子电池的正极材料 3

1.5 LiCoVO4正极材料的结构特点 4

1.6 LiCoVO4的制备方法 5

1.6.1 固相法合成LiCoVO4 5

1.6.2 微波法合成LiCoVO4 6

1.6.3 溶胶—凝胶法合成LiCoVO4 6

1.6.4 热液法合成LiCoVO4 6

1.6.5 水热法合成LiCoVO4 6

1.7 LiCoVO4的改性方法