摘要橄榄石型LiCoPO4正极材料合成条件相对比较简单，能耗低，有利于进一步投入生产和应用，被认为是一种极具应用潜力的动力型锂离子正极材料，但因其电子导电率低和锂离子扩散系数低导致其循环性能和倍率性能较差，阻碍了它的商业化应用进程。本文采用微波溶剂热法合成LiCol-xFexPO4（x=0.2，0.3，0.4，0.5）正极材料并对其进行改性研究，采用XRD表征方法和恒流充放电、循环伏安和交流阻抗测试对其电化学性能进行分析比较。57441

以LiOH、Li3PO4和CoSO4为原料，蔗糖为碳源，FeSO4为取代铁源，通过碳包覆和Co位取代复合改性制备LiCol-xFexPO4/C（x=0.2，0.3，0.4，0.5）材料，取代后的样品属于单一的橄榄型晶体结构，没有明显的杂质峰，说明少量的Fe取代不会改变LiCoPO4的晶型结构。当x=0.5时LiCo0.5Fe0.5PO4/C材料显示了良好的充放电性能、循环性能、倍率性能和最低的电化学阻抗，其0.1C下第三次循环下的比容量为104mAh/g，比能量分别为405.8mAh/g，比其他铁取代材料都要高，说明LiCo0.5Fe0.5PO4/C电极具有最佳的充放电性能。循环伏安和交流阻抗测试表明，LiCo0.5Fe0.5PO4/C电极具有最低的电化学极化作用和电化学阻抗，循环性能测试表明，LiCo0.5Fe0.5PO4/C电极具有最佳的循环性能，0.1C充放电循环20次后容量达到初始容量的88.5%。

毕业论文关键词：锂离子电池；正极材料；微波溶剂热法；碳包覆；电化学性能 

Abstract Olivine type LiCoPO4 cathode material synthesis conditions are relatively simple， low energy consumption， is conducive to further investment in production and application， is considered to be a kind of highly applied potential of power type lithium ion cathode material. However， due to its low electronic conductivity and low lithium ion diffusion coefficient， its cycle performance and low rate performance is poor， which hinders its commercial application process. In this paper， the microwave solvothermal synthesis LiCol-xFexPO4（x=0.2，0.3，0.4，0.5）cathode materials and the was modified and characterized by X-ray diffraction (XRD) method and constant current charge discharge， cyclic voltammetry and AC impedance test on the electrochemical performance of comparative analysis.

LiCol-xFexPO4/C（x=0.2，0.3，0.4，0.5）materials were prepared by LiOH， Li3PO4 and CoSO4 as raw materials， glucose as carbon source， FeSO4 as the substitute of iron， and Co was prepared by carbon coating and substitution. The substituted samples belong to a single olivine type crystal structure， with no obvious impurity peaks， which indicate that a small amount of Fe substitution does not change the crystal structure of LiCoPO4.LiCo0.5Fe0.5PO4/C material shows good charge discharge performance， cycle performance， rate performance and the lowest electrochemical impedance when x=0.5.The specific capacity of the 0.1C under the three cycles was 104mAh/g， and the specific energy was 405.8mAh/g， which was higher than that of the other iron substituted materials， indicating that the LiCo0.5Fe0.5PO4/C electrode had the best charging and discharging performance. Cyclic voltammetry and AC impedance tests show that the LiCo0.5Fe0.5PO4/C electrode has the lowest electrochemical polarization and electrochemical impedance. Cyclic performance tests show that the LiCo0.5Fe0.5PO4/C electrode has the best cycling performance， and the capacity of the 0.1C charging and discharging cycle is 88.5% after 20 times of the initial capacity.

Keywords: lithium ion battery; cathode material; microwave solvent thermal method; carbon coating; electrochemical performance 

目录

1 绪论 1

1.1 研究背景 1

1.2锂离子电池的发展现状 1

1.3锂离子电池的工作原理