性能的影响
(华南理工大学 材料科学与工程学院，广州 510640)
摘 要: 以有机(柠檬酸铁)和无机(Fe2O3或Fe3O4)三价铁混合物为铁源，以有机铁源中的有机酸根为碳源和还原剂，通过固相−碳热还原法制备LiFePO4/C正极材料，考察无机三价铁源对正极材料结构和性能的影响。采用XRD、SEM和恒流充放电测试等方法对正极材料的结构、表观形貌及电化学性能进行研究。结果表明：以Fe2O3为无机三价铁源合成的LiFePO4/C材料的晶相单一、晶粒尺寸较小、电化学性能较好，以0.1C放电时，其第三次放电比容量达136 mA∙h/g，循环20周后基本无衰减；而由Fe3O4为铁源制得的材料中含有其它杂质相，晶粒尺寸较大，电化学性能较差，以0.1C放电倍率放电时，其第三次放电比容量仅为118 mA∙h/g，循环20周后衰减近17%。
关键字: LiFePO4；锂离子电池；正极材料；碳热还原法；三价铁源
LiFePO4/C prepared by carbothermal reduction method
（College of Materials Science and Engineering, South China University of Technology, Guangzhou 510640, China）
Abstract:LiFePO4/C cathale material were synthesized by solid state-carbothermal reduction method using organic (citrate ferric) and inorganic (Fe2O3 or Fe3O4) trivalent iron compounds as iron precursors and using the organic acid radical in organic iron precursor as both reducing agent and carbon source. The influences of inorganic Fe3+ sources on the structures and performances of the material were investigated. The structure, morphology and electrochemical properties of LiFePO4/C were analyzed by XRD, SEM and galvanostatic charge-discharge method, respectively. The results indicate that the sample synthesized by Fe2O3 has fine particle size, single crystal structure and excellent electrochemical performances, the third discharge capacity remains 136 mA/h∙g at 0.1C with almost no capacity fading after 20 cycles. While the third discharge capacity of sample obtained from Fe3O4 with large particle size and some impurities is only 118 mA∙h/g at 0.1C, with about 17% capacity fading after 20 cycles.
Key words: LiFePO4; lithium ion battery; cathode material; carbothermal reduction method; trivalent iron source
