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摘要：本实验采取以还原铁粉为铁源，磷酸为磷源，氢氧化锂为锂源，并加入石墨烯进行碳包覆制成溶液，采用喷雾干燥技术获得了磷酸铁锂前驱体粉末。经700℃高温煅烧后实现了石墨烯与磷酸铁锂的均匀包覆。研究了不同的石墨烯添加量对磷酸铁锂正极材料的结构和电化学性能的影响。通过X射线衍射仪、扫描电镜、热重对磷酸铁锂正极材料进行物相、形貌及热力学性能的表征与分析。研究结果表明：相比于纯LiFePO4，LiFePO4/石墨烯复合材料的颗粒表面包覆了一层薄薄的导电碳网，石墨烯包覆后的LiFePO4材料的电荷转移电阻显著降低，锂离子扩散路径缩短，循环性能得到较大提高。电化学测试结果表明，当石墨烯添加量在3%的时候获得了性能优异的电池原料，在0.2C的倍率下，电压平台在3.42V左右，首次充电比容量为173.3mAh.g-1，首次放电比容量为167.4mAh.g-1。由此表明，加入石墨烯后合成所得的锂离子电池正极材料磷酸铁锂具有良好的电化学特性，可以在动力电池领域应用。19995
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毕业论文关键词： 磷酸铁锂；石墨烯；喷雾干燥；电化学性能
Studies of electrochemical performance of composite material LiFePO4/Graphene
Abstract: The paper take iron powder, phosphoric acid and lithium hydroxide as raw materials, add the graphene for carbon coating solution, use the spray drying method for a lithium iron phosphate precursor powder, and achieve uniform graphene-coated lithium iron phosphate after 720 ℃ calcination. Studied structures and electrochemical properties of the cathode material by adding different amounts of graphene. The samples’ phase, morphology and thermal properties were characterized by XRD, SEM and DSC/TG. The results show that compared to pure LiFePO4, the graphene-coated LiFePO4 material can significantly reduce the charge transfer resistance, shorten the lithium ion diffusion path and greatly improve cycle performance as its surface coated with a thin layer of conductive carbon network. The electrochemical test results show that the most excellent performance of the battery materials got when the amount of graphene in 3%. Under the ratio of 0.2C and the voltage plateau at about 3.42V, the first charge capacity was 173.3mAh.g-1, the first discharge capacity was 167.4 mAh.g-1. It is suggested that after adding graphene, the iron phosphate cathode material for lithium ion batteries lithium has good electrochemical properties and can be applied in the field of battery power .
Key Words: lithium iron phosphate; graphene; spray drying; electrochemical performance
目录
摘要 i
Abstract i
目录 iii
1 绪论 1
1.1 锂离子电池简介 1
1.1.1 锂离子电池的发展与用途 1
1.1.2 锂离子电池的充放电原理 1
1.2 磷酸铁锂正极材料 2
1.2.1 磷酸铁锂的结构 2
1.2.2 磷酸铁锂的制备 2
1.2.3 磷酸铁锂存在的问题 4
1.2.4 磷酸铁锂的改性方法 5
1.3 实验意义及课题内容 6
1.3.1 实验意义 6
1.3.2 课题内容 7
2 实验部分 8
2.1 实验原料与试剂 8
2.2 实验用仪器设备 8