(中南大学 冶金科学与工程学院,长沙 410083)
摘 要: 以FeSO4·7H2O,H3PO4,H2O2和NH3·H2O为原料合成FePO4·xH2O前驱体,考察制备过程溶液pH值对合成FePO4·xH2O前驱体性能的影响;将Li2CO3,FePO4·xH2O和乙炔黑球磨混合,通过低温固相反应合成LiFePO4。用X射线衍射和扫描电镜对FePO4·xH2O和LiFePO4进行结构和表面形貌表征,研究不同pH值条件下合成的FePO4·xH2O前驱体为原料对制备的LiFePO4电化学性能的影响。结果表明:溶液pH值1.5时制备的FePO4·xH2O中含有少量Fe(PO4)2(OH)2杂质,当pH分别为2、3、4和5时,合成的FePO4·xH2O均为纯相。pH值为2左右合成的FePO4·xH2O前驱体制备出的LiFePO4具有良好的电化学性能;其振实密度达
关键字: 锂离子电池;LiFePO4;PO4•xH2O;电化学性能
(School of Metallurgical Science and Engineering, Central South University, Changsha 410083, China)
Abstract:FePO4•xH2O precursor was synthesized from FeSO4•7H2O, H3PO4, H2O2 and NH3•H2O under various pH value. LiFePO4 cathode material was then synthesized by low temperature sintering of the homogeneous mixture of Li2CO3,acetylene black and FePO4•xH2O. The effect of the solution pH on the performance of FePO4•xH2O was characterized. The structures of FePO4•xH2O and LiFePO4 were characterized by XRD and SEM. The effect of the solution pH on the electrochemical performance of LiFePO4 was discussed. The results show that no impurities exist in the FePO4•xH2O synthesized at pH value ranging in 2 and 5. LiFePO4 made from FePO4•xH2O precursor synthesized under the condition that the solution pH is about 2 show excellent electrochemical performance, and the tap density reaches 1.11 g/cm3.
Key words: lithium ion batteries; LiFePO4; FePO4•xH2O; electrochemical performance